Table of Contents

Green Roofs

Before actually into the thick of the topic, we need to understand the need for the green roos. Perhaps some statistics will help us illustrate this.

  • The rate of construction and ‘construction utilisation’ has more than tripled in developing countries in the last two decades.
  • Land reclamation, has emerged as the only option of dealing with this issue. However, land reclamation is not only extremely expensive, it is also largely detrimental to the environment.[1]

As a result of increasing levels of construction projects and various man-made activities, vast landscapes have been cleared out of vegetation in the last century or so. These land areas, once teeming with vegetation and animal life that depended on it, are not converted into ‘concrete jungles’ that have no positive impact on the environment.

Every construction project, regardless of its nature, size and structure, has a detrimental impact on environment, in that it requires immense amount of energy utilisation, natural resources and of course, a clean and clear piece of land. Thus, every construction project, even before it is actually constructed, has a negative environmental footprint, something that ecologists call ‘green deficit’ or ‘environmental negative credit’.

Because of this very green deficit, there arises a need to compensate for it in one way or another in order to ensure that buildings less indebted, environmentally speaking. Many multinationals such as PepsiCo, IBM, Google and Facebook actively try to tackle this issue as the green deficit they have is quite substantial. A common way, over the last few decades, has been to actively fund green projects, in a way to make amends.

For individuals, on the other hand, compensating for their construction green deficit can be difficult and expensive. Gardening is one way however, not everyone has the luxury of both time and space.

‘Green roofs’ can be considered to be a great alternative in this regard. Green roofs have the ability to account for the environmental dues that a construction project may have had, all the while not requiring any additional piece of land.

[1] Statistics elicited from the UN Climate Council Reports of 2012, 2013 and 2014

Green Roofs: The Concept & History

It may be a surprise to many the concept of a ‘green roof’ (or ‘green roofing’) is not a novel one. It’s true that the sophistication green roofs possess is a direct result of advancements in technology, however, the idea of green roofs can be traced back many centuries. In Scandinavian countries, especially Norway and Sweden, sod roofs have been a fairly common. Sod roofs are roofs that are designed to blend in perfectly with the surrounding vegetation in summer, as well as being a great medium for heat retention during harsh and cold Scandinavian winters. Many Nordic mythological stories and Viking tales are known to make references to sod roofs that were ground above ground. The next sub-point in this article will be helpful for the readers who wish to know more about these sod roofs and their history.

While talking of mythological tales, it would be fitting here to mention that J.R.R. Tolkien, the famous British author and creator of the Middle Earth, borrowed the idea of green roofs in many of his books. His most famous creations, the Hobbits, are known to live in burrows among hills that have artificially crafted green roofs.

Reverting to the Scandinavian roots of green roofs, it’s worth noting the Vikings are generally known to be wanderers, and not settlers. So, having an easily manufactured green roof, made entirely of vegetation, must have been the reason for using green roofs.

Going further a few centuries ahead, rapid advancements in tech, industry, digitization and relevant manufacturing methods, green roofs have, today, become much more than just crude vegetation. Today, green roofs can be manufactured, installed, transported, custom designedand even gardened. Due to those advancements, green roofs are capable to solving many problems at once. (more about the benefits below).

Sod Roofs

As mentioned in the above sub-point, sod roofs in Scandinavian culture are definitive precursors to green roofs. Sod roofs have many alternative names, from grass roofs to turf roofs and from Finnish roofs to Viking roofs.

Researchers have concluded that the tradition of covering wooden or log houses in Scandinavian countries with sod roofs is a fairly common one that has been in existence for centuries. It’s interesting to know that this tradition, unlike others, wasn’t found in other parts of the world until the late 19th century.

A sod roof is a wooden roof or a log roof with a slope that is not too steep, but has enough of a slant to drain water, and is covered with one or more layers of birch branches, leaves and barks. These layers of birch branches are then covered with a specially grown layer of sod that can then be maintained throughout the summer.

A Typical Scandinavian Sod Roof

Figure 1: A Typical Scandinavian Sod Roof (Image Credit:

In the context of Scandinavian countries, sod roofs are fashionable as well as useful:

  1. easy to construct.
  2. very low to no maintenance.
  3. strengthen wood logs that make up the roof
  4. efficient insulators of heat

Green Roofs: Recent History and Present Day Status

Green Roofs in NYC
Figure 2: Green Roofs in NYC (Image Credit: InHabitat)

Modern day adoption of green roofs was predominantly started in Europe, in particular Germany. Germany has been at the forefront of embracing greener technologies for over three decades, even before it was advocated globally. As a result of widespread education about environmental issues, it is estimated that over 10% of all roofs in Germany are green. This is widely believed to be the highest percentage in the world.

In other European countries like Netherlands and Belgium, green roofs are found in many villages. As mentioned earlier, Scandinavian countries, too, boast of a high degree of green roofs – albeit the chief reason for this lies more in tradition than anything else.

In the United States, green roofs adoption is low. That being said, it’s well worth mentioning that extensive efforts are being made, especially in states that have conducive weather for plant growth (Florida, Georgia, California, Alabama etc.). With sustained efforts, one can expect green roofs to be a prevalent product in the coming times. Many ecologists have advocated for the inclusion of green roofs in codes of construction, such as the the International Building Code. The present growth rate of the green roof industry is estimated to be around 10% to 12%. Experts have expressed a need to improve this rate to at least 20%.

Brown Roofs: An Extension of Green Roofs

The idea behind green roofs is to utilize vacant space for purposes of growing vegetation and making a positive impact on the local environment. As an extension of this concept, another idea – termed as brown roofs by researchers and scholars – has been proposed and even implemented in certain parts of the world (most notably Germany and Australia). The idea entails using rooftops for promoting local biosphere. In many places, as a direct result of diminishing plant life in localities due to increasing construction results into a severely damaged ecosystem where many of the species and life forms suffer. To mitigate the effect, building rooftops are used as ‘growing media’ or ‘artificial habitats’ for local species. The outcome is the assistannce to the local biosphere. Although the idea of brown roofs is unique, more research and testing needs to be done, before it is accepted as mainstream. In the sense that brown roofs use rooftops, they can be considered an offshoot of green roofs.

How Do Green Roofs Work?

The functionality of a green roof is not different than that of any sustainable artificial ecosphere (for example, greenhouses or artificial beehives).

Typical Green Roof Structure

A typical green roof is a multi-layered structure. Depending upon the application and complexity of construction, it can contain layers that can number between 3 to 25. Even though green roofs with many layers are not quite common, they serve a greater purpose in terms of allowing researchers and academics to evaluate various aspects of growth and potential for vertical as well as horizontal scalability of ideas.

A typical green roof consists of nine to ten layers. The following figure depicts the cross section.

Cross Section of a Generic Green Roof

Figure 3: Cross Section of a Generic Green Roof (Image Credit: Purdue University)






The layers that make up a green roof, thus, are (from the bottom to the top):

  1. Roof (Support Surface)

    The roof acts as the support surface that all of the other layers rest on. It is a standard practice to install layers that do not exceed the 60% – 70% the max frame load.

    In newer buildings, however, better weight management is achieved through weight distribution on additional support beams.

  2. Vapor Control Layer

    The second layer typically consists of a vapor control layer. This layer goes on top of the first layer and is typically made of up of polymerized membranes that do not allow vapor in.

  3. Insulation Layer (Optional)

    An optional layer is thermal insulation. It is not required and hence, is deemed an optional layer. When present, however, thermal insulation can contribute significantly to the cross sectional thickness of a green roof.

    Thermal insulation layers are generally made of foam based materials that can block the sectional flow of heat by reducing conductive, convective and radiative heat losses. A layer of foam reinforced by thick polymeric plastic sheets (like HDPE) can work as a an insulator and prevent heat from being transferred to or from the support layer i.e. the roof.

    Insulation layers are of great utility in cold climates. They can not only block the escape of indoor heat, they can also provide a much needed thermal equilibrium that helps heating equipment like radiators and heaters (indoors) performing at an optimum efficiency, saving energy.

  4. Reinforcement Layer (Support Layer)

    The insulation is followed by a moderately thick, but rigid and strong support layer. This layer is generally 20 to 40 mm in thickness and acts as a solid, rigid support for the assembly.

    Using a waterproofed sheet of ply as a reinforcement layer, is considered to be a common and standard industry practice.

  5. Waterproofing Layer(s)

    Top of the reinforcement layer, another thin layer of waterproofing material (hardened polymers) is added. This layer prevents seepage of water into the layers below.

    It was a common practice to use waterproofing paint in place of hardened polymers. However, the fact that a layer of hardened polymer can act as a waterproofing agent as well as a root blocker has prompted industry experts to discard the use of waterproofing paint. Having a root blocking layer in place ensures that roots of the vegetation planted on a green roof do not penetrate the roof itself. Again, this is important because penetration of roots into the body of a roof can seriously compromise the strength and the structural integrity.

  6. Drainage Layer

    This is perhaps the most significant layer that makes up a green roof. If the drainage layer is not designed optimally, it can quickly render the whole exercise ineffective as the vegetation cannot sustain its own growth in unfavorable moisture conditions.

    It is a common practice to use standard gardening methods while designing the drainage layer for green roofs. It should also be noted here that the design and construction of a drainage layer is dictated by many factors such as:

    • Type of the vegetation being grown
    • Weather
    • Availability of water
    • Retention factor required for the optimum growth

    Typical composition of a drainage layer consists of:

    • Sand
    • Gravel
    • Shredded plastic
    • Wood chips (rare)
    • Metal fragments

    Drainage layers are generally constructed with a subtle inclination that mimics the original inclination of the roof so that the existing rainwater drainage systems on the roof can be used to drain excess water.

  7. Membrane Layer

    This is the most fragile and delicate layer of the entire installation. It also happens to be the largest contributor to the overall cost of a green roof (in terms of weight to cost ratio).

    A membrane layer is a layer of semi-permeable polymeric or organic membrane that filters out soil and other debris from excess water seepage, allowing largely filtered stream of water to be drained. The presence of membrane layers has two advantages:

    • The layer blocks soil or growth material from getting washed out.
    • Crudely filtered drainage stream is easier to recycle and treat for further usage. 

  8. Growth Medium

    Growth medium, to put it in the simplest of terms, is what you see on a green roof.

    In most cases, growth medium is predominantly a locally sourced layer of soil that is enriched by fertilizers, minerals and bio-synergetic organism such as earthworms.

    The growth medium sustains the growth of the vegetation. The composition of growth / soil medium is generally decided by ‘trial and error’ methods. The reason for this is in many cases, a green roof comprises of many various types of plants. What’s favorable for one plant may be not so favorable for another. Considering this aspect is perhaps the biggest challenge while designing a green roof because, unlike natural soil and ground, a green roof has only so much resources.

Functionality of Green Roofs

A typical green roof constructed on the rooftop of a residential building can vary in thickness from a range of 5 inches to 10 inches. In certain cases, green roofs that are as thin as 2 inches can also be developed. However, these are often ‘portable’ green roofs and are constructed in pre-fabricated trays that are housed on a rooftop. These portable green roofs are often used to grow sod and grass and other finer vegetation that doesn’t require much of a growth medium.

Industrial level green roofs can, at times, be constructed with over 20 layers and are known to range in thickness from 15 inches to over 30 inches.

  1. Plantation

    Vegetation on a green roof is generally added ten or twelve days after the construction of other layers. The idea behind this is the delay allows all the layers to cure.

    In some parts, the growth medium in a green roof is left in a sodden condition for a period of three to four days and then allowed to dry completely to ensure a uniform porosity profile.

    In rare cases, especially on a large scale, pre-planted green roofs can be installed on rooftops, much like ready-to-roll grass turfs. These green roofs are typically thinner than site-planted green roofs and are mainly used for beautification purposes, other than anything else.

  2. Nutrition

    Nutrition is an important aspect of maintaining a healthy roof and is usually achieved through fertilizers.

    After a period of about 12 to 18 months, it is recommended that green roofs be ‘refurbished’ either by transferring the existing vegetation to a new medium, or by entirely removing it and planting a new batch. This is necessary as the nutritional profile diminishes in quality.

  3. Irrigation

    There are three main problems that are commonly faced regarding irrigation:

    1. Maintaining a uniform level of moisture in the growth medium is a problem as the growth medium has no access to groundwater. Hence, one needs to keep tweaking the water levels according to the weather.
    2. Drainage of excess moisture is something that can be taxing on the entire assembly, as excess water tends to drive nutrients away from the growth medium. Also, the slope of the roof plays a big part in the efficiency of drainage. If the roof has a slope of 5% or higher, it can become very difficult for the growth medium to retain uniform levels of moisture.
    3. Not allowing excess water to drain, on the other hand, results in stagnation. Stagnated water invariably leads to root rot and growth of parasites.

    To counter these problems, many innovations have been designed. 

    1. Aautomate the ingoing stream of water based on the present level of moisture in the growth medium. Sensors present at strategic points in the growth medium are used to measure the present level of moisture. Depending upon this reading, the ingoing stream of water is adjusted. This is, however, an industrial solution, and is not exactly feasible at domestic level.
    2. To ensure efficient irrigation, use of drip irrigation or channel irrigation is advocated by experts. Drip irrigation is perhaps the best option as it negates the possibility of local excess of moisture. To act against the existing slope of the roof, offsetting measures can be adopted while structuring and installing bottom layers, most notably the drainage layer.
    3. To counter the possibility of stagnation, internal channelling methods can be used. Channelling methods allow for the growth medium to retain enough moisture, while draining excess water through orifices that are designed as per requirements. Internal channels can also be beneficial for air circulation inside the growth medium, thereby helping avoid root rot.

Green Roofs: When are they feasible?

Green roofs, even though extremely useful and positive in their green footprint, are not always a good or viable idea. There are some basic criteria that need to be assessed before implementing green roof.

Construction and Strength Criteria

The very first criterion that needs to be checked before installing green roofs, especially in old building is the strength of the roof. Typically, green roofs (domestic versions) are known to weight in the range of 50 lbs per square foot (at about 5’’ thickness). Thicker green roofs weigh in the range of 100 lbs per square foot (at about 12” of thickness).[2] So, it should be quite clear that green roofs can put considerable normal and lateral load on the roof because of this weight. Understanding this limitations of a roof in handling these stresses is important before installing green roofs.

[2] Weight ranges are only indicative. With heavier vegetation and water saturation, weight of a green roof per square foot can significantly increase.

Types of Vegetation

Another thing to consider before installing a green roof is the viability of vegetation. For domestic purposes, best choice of vegetation can be smaller shrubs and/or bushes coupled with variants of grass. Plants that are short in structure, shallow in growth, have limited spread and do not require extensive soil depth for the proliferation of their root network can thrive on green roofs.

Here is a list of some common plants that can grow extra-ordinarily well as a part of the green roof ecosystem.

  • Sedum
    An exemplary Sedum Green Roof
    Figure 4: An exemplary Sedum Green Roof (Image Credit:

    Sedum is perhaps the best known genus of plants that can be easily grown on green roofs. The most distinguishing characteristic of the Sedum genus is that the species it consists of are all shallow in growth and have succulent, uniform leaf growth. In addition, Sedum genus plants do not have much underground root network to speak of, as they tend to thrive on superficial nutrients. Because of these properties, plants in this genus are quite well suited for green roofs.

    Sedum plants are generally very attractive in appearances. They have very peculiar foliage and flower patterns and they do not require any considerable maintenance. They have very little water and nutrient requirements and can be easily transferred to other media if the need arises.

    Some common examples of Sedum genus flowering plants are:

    • Stonecrops
    • Goldmoss
    • Ruby Glow
    • Matrona
  • Ice Plants

    Ice plants are another excellent choice for green roofs. Ice plants are short, thick leaved flowering plants that can act as a roof cover. They often have brightly colored flowers that can further increase their value as a green roof plant.

    Like Sedum, Ice plants have succulent leaves and are known to survive without significant moisture for sustained periods of time. They entail little to no maintenance at all and can survive long periods of drought.

    Some common examples of Ice plants are:

    • Living stone
    • Delosperma
    • Yellow Hardy
    • Cooper’s Plant
    • Starburst
    • Sunburst
  • Vegetables

    Many people are taken up with the idea of having access to home-grown vegetables. While it’s not always possible to have such vegetables all year round, it’s certainly possible to enjoy these wholly organic delights that you yourself have grown at home every once in a while, if you plant them on the rooftop of your home.

    Most of the domestic vegetables can be successfully grown on roof tops as they are not deep rooted and can be planted with ease. The best course of action, as many experts advise, is to divide the rooftop into alternate vegetable and grass/flowering plant sections. This ensures that the resources in the substrate are distributed more evenly throughout the roof, instead of getting concentrated locally.

Area to be Covered

While probing the possibility of installing or growing a green roof, another important thing that needs to be considered is the total area that needs to be covered.

In normal residential buildings and households, a green roof can be a great small scale value addition that can be greatly beneficial in the long run. On large scales, however, various aspects like return on investment and maintenance aspects, along with the capital that goes into growing a green roof at such scales need to be assessed with a good deal of deliberation.

Availability of Resources

Needless to say, before installing or growing a green roof, it must be ascertained that there is an adequate availability of resources to sustain the roof. These resources generally include water, sunlight, skilled labor for maintenance, fertilizers, technology etc.

Main Reason for Implementation

Before actually considering the implementation of a green roof, the chief reason for it needs to be pondered over very carefully. Even though it’s true that green roofs of today can be easily set up and removed, it’s certainly in the best interest of the investor to choose wisely. In domestic condition, the chief reason for implementation is beautification coupled with utility – and quite rightly so. Green roofs on houses can not only contribute marginally positively to the environment, they can also enhance the beauty of the house.

On the other hand, green roofs that are to be designed and set up over large roof tops (on industrial levels, or on the roofs of community buildings), the chief driving force should be the compensation of negative environmental footprint that can be directly attributed to the building.

If the incentive behind setting up a green roof is clear, it becomes easier for the investors to understand the level of economic commitment that the whole project should be accorded with.

Manifold Advantages of Green Roofs

The advantages of green roofs are manifold, to say the least. As mentioned in the introductory portion of this article, the major motivator for the idea of a green roof to be adopted in many countries of the world is the ecological attractiveness of the concept. Along with and in extension of this very advantage, there are quite a few other advantages that green roofs entail. These advantages will be listed and discussed in brief in this sub-point.

Environmental Benefits of Green Roofs

Green roofs are best known as roofs that can help buildings reduce their environmental deficit by restoring the green balance that was disturbed when the land was claimed for construction.

However, to understand exactly how green roofs work in this regard, we need to understand the whole gamut of environmental benefits that green roofs entail. 

  • Compensating for the Carbon Footprint

    This is the most obvious of advantages that green roofs have, and perhaps the most attractive as well – especially when we consider the present times. The need for doing anything and everything that we – as a species – can in order to curb or compensate in the least for all the detrimental carbon footprint our activities leave on this planet has never been direr. Green roofs can be considered a little step forward in this direction. The real attraction for green roofs in battling climate changes lies in the fact that green roots are very highly scalable. Green roofs can be extended to most rooftops in the world, converting them into small-scale environment restorers.

    Green roofs have tremendous potential to reduce the impact of carbon emissions in a local context. Considered cumulatively, the positive environmental impact of green roofs can be easily understood to be quite high, if widespread adoption is initiated.

    Because of the very virtue of being ‘vegetation’, green roofs are active photosynthesizers. Hence, they utilize carbon dioxide and nutrients from the substrate and convert these into active useable energy with the help of sunlight. In the process, oxygen is released. Covers of green roofs are also known to capture other greenhouse gases like methane by way of adsorption and assimilation.

  • Restoration of Urban Habitat

    Careful urban observers would agree with the statement that the unprecedented prevalence of buildings of various kinds has, quite literally, robbed precious habitat from thousands of species of organisms. These organisms are eventually pushed into a situation in which they have nowhere else to resort to. The situation becomes so dire that, at times, certain species are forced on the brink of extinction. Perhaps the best known example in this regard is that of the Domestic Sparrow (also known as House Sparrow). Ever since urban areas around the world have gone on building sprees, leaving no acre unbuilt, there has been a marked decline in the sightings of sparrows that used to be very commonly observed earlier. Prominent media houses have even gone on to announce campaign prizes for carrying out case studies in this connection.  The point being made here is that green roofs, by restoring local habitat to a certain degree, can offer local organisms a suitable shelter. From birds to insects, many species who otherwise find it impossible to find shelter in urban areas can benefit immensely from green roofs.

    Insects, bees, butterflies, domestic birds and other related microorganisms can thrive with ease on and around green roofs. This can, to some extent, help in the restoration of the local habitat that was disrupted due to the construction of the building.

  • Plant Conservation

    Another effective way in which green roofs can positively influence eco-systems locally is by allowing for plant conservation. Couples with brown roofs (discussed in the introductory parts of this article), green roofs can provide a great platform to conserve local species of plants that are rarefying because of various man-made activities. Such local plants, as suited on various green roofs, can be planted, grown and allowed to thrive in order to save them from further rarefaction, and perhaps, even extinction.

    One prominent example that has been a guiding light for plant conservationists is the Chicago Botanical Garden. The garden features a vast expanse of green roof – over 16,000 sq. ft. in spread – that is single-handedly responsible for saving over 50 species of plants from experiencing extinction. The green roof garden is a thriving living laboratory of sorts, visited by thousands of tourists every year.

    This effect, at much smaller and private scales, can be easily achieved at homes.

  • Natural Filtration of Rainwater

    Rainwater of the day, unlike fifty years ago, is not exactly pure. It is contaminated with a number of pollutants that range from dust particles to dissolved chemicals. These pollutants get mixed with groundwater reserves when such polluted rainwater is allowed to seep into them.

    Even though it’s next to impossible to curb this phenomenon unless we curb pollution, it’s certainly possible to somewhat curtail it by allowing rainwater to pass through the substrate bed of green roofs. Substrate best (i.e. growth media) absorb and adsorb most pollutant, leaving a purer stream of drain water stream that can either be used through recycle or just allowed to be drained into the ground. Another subtle – yet important – effect that green roofs have is that they significantly reduce the momentum of water runoff. Reduction in the momentum of runoff streams robs them of potential to cause erosion via friction. Thus, it can be said that green roofs have the potential to improve the overall quality of runoff water streams.

  • Mitigating Local Heat Spikes

    People who have lived in both rural and urban areas would know that it’s certainly hotter in comparison in urban areas than in rural areas. This is due to the fact that rural areas are generally covered with a lot of vegetation that combats any presence of greenhouse gases in the surrounding atmosphere. In urban areas, however, there is little to no presence of vegetation. Furthermore, many man-made activities in such areas – from industries to offices and shopping malls to movies – contribute to the overall emission of greenhouse gases. Increased emission and reduced absorption of greenhouse gases leads to local heat spikes – also known as Urban Heat Island Effect.

    Green roofs can help urban communities combat this effect by providing invaluable absorption capabilities. Having a green roof atop every house and building in a city can easily bring urban, local heat spikes down by a significant degree.

  • Reuse and Recycle

    Reusing and recycling are deemed to be two sure-fire ways of dealing with material and resources shortages. Reusing helps in saving up on processing costs of materials while recycling helps in saving up on the materials themselves. Even though these two tenets have been widely advocated, many people still are clueless regarding the ways in which they can embrace these ideas at domestic levels.

    Green roofs can provide answers to some of these questions. The drainage layer of green roofs is often made up of recycled plastic, discarded gravel and shredded rubber tires. Rubber and plastic, in particular, are very difficult to get rid of when their active utility life is over. It can be a practical solution then to use such materials in green roofs that will help reduce the green deficit.

  • Eco-Education

    Eco-Education is a concept that has become deep-rooted in urban communities in last few years. Eco-Education involves educating oneself through various media on numerous environmental issues on local as well as global levels, and learn more about one’s part in the fight to tackle these issues.

    Green roofs provide an easily accessible learning center of sorts for all of us, especially young children. By learning why we need green roofs and how they help keep our environment positively influenced, we can put ourselves in a better position to learn global environmental problem with clarity and deep understanding.

  • Energy Savings

    Another one of direct benefits of green roofs comes through the fact that green roofs are known to offer substantial energy savings. Even though it is true that these savings are not realized in one year, over the course of many years, the cumulative savings can be very attractive.

    Green roofs, by virtue of their various layers, provide excellent insulation to the roof of the building. It is a well-known fact that roofs can be the biggest means of escape for indoor heat as they are generally left open and do not have any other layer to stop this loss of heat. Green roofs provide just the perfect solution for this problem by acting as an active insulator. This is especially of use in cold climates where indoor heating accounts for the bulk of the energy expenditure of a building. Green roofs can not only help save energy in this regard, they also further contribute to the environment by curtailing the use of electricity by the building.

    Alternative green roofs, as mentioned earlier, employ means like solar photovoltaic panels to utilize vacant roof space. The said infrastructure is streamlined for utilizing solar energy in order to generate a cleaner source of electricity. Use of renewable energy is subsidized in most states in America, and hence, making vacant rooftops greener by way of combining vegetated roofs and solar roofs can be a very attractive solution for homeowners as well as businesses – both environmentally and economically. 

Financial Benefits of Green Roofs

Apart from being extremely beneficial in environmental sense, green roofs are also very beneficial in financial sense. It should be reiterated at this point that like most long term investments, financial benefits of green roofs can be evident and attractive only when they are considered over a period of years. At about 5 to 7% estimated annual return on investment, green roofs can be considered akin to regular bank savings or most stock market investments of low risk.

Financial benefits of green roof arise from various factors. The most prominent of those have been detailed below.

  • Reduction in Construction Costs

    Green roofs, it may come as a surprise to many, actually benefit buildings by reducing various construction costs. Even though green roofs entail a certain level of initial capital investment, it is quite interesting to state here that they help building owners avoid various subsequent construction costs like roofing maintenance costs and roof insulation costs.

    Having green roofs in place also helps owners avoid investing money in expensive screed infrastructure. Green roofs entail zero falls and hence can easily be considered as viable alternatives for screeds. Improved performance of the building in other areas such as acoustic proofing and rain/storm water management due to green roofs can allow owners to spend less on external performance improvement specialty units.

  • Utilities

    Green roofs, over the course of years, can help the building spend lesser energy – especially for heating purposes. Green roofs improve the insulation of roofs quite impressively, thereby reducing the total loss of heat that can be directly attributed to the surface of the roofs. As this loss is minimized, quite understandably so, lesser energy is needed to be spent to keep the indoor temperature at a high enough point.

  • Subsidies and Incentives

    Green roofs are considered as a Viable Green Technology by the Environmental Protection Agency (EPA) of the United States. This means that green roofs are eligible to receive various grants, subsidies and incentives that the EPA (on behalf of the Federal Government of the United States) and various state and local governments offer. These incentives are meant to encourage the use and adoption of green technologies at households and businesses in order to endorse greener ways of operation.

  • Planning Expediting

    Getting planning permits for new construction projects can be a very tough proposition in some parts of the country. This is true especially in already heavily urban areas. There are newer rules and norms put in effect every few years so as to account for various environmental laws. It has been a unanimously positive experience of many designers and planners that inclusion of green roofs in the design of a new construction project can expedite the whole planning permission procedure as green roofs allow the design to become environmentally laminar – a virtue that most planning offices hold in high regard.

  • Increments in the Property Value

    Green roofs turn out to be a positive addition in an overall sense for almost every building imaginable. Green roofs provide a valuable patch of greenery that houses in urban areas cannot afford for the lack of land space. These green patches can, in turn, help the owners financially by upping the value of the building in the property market.

Constructional Benefits of Green Roofs

Along with providing a host of ecological, environmental and financial benefits, green roofs have some benefits that directly influence the constructional existence of a building. These discussed in brief in the following points.

  • Rain/Storm Water Management

    It is a very difficult proposition to manage rain/storm water in areas that experience heavy rainfall, even for a brief window in the whole year. Managing the streams of rain/storm water is difficult because of:

    1. Erosion that incoming streams cause
    2. Seepage of moisture into building walls and roof(s)
    3. Water stagnancy
    4. Associated perils like mold and heightened breeding of insects like mosquitos

    To deal with these issues in one go, green roofs prove invaluable. It is estimated that a green roof that covers at least 60% of the roof area can easily reduce the run off volume of rain/storm by up to 50%. Green roofs, on account of their various levels and efficient drainage system, can manage rain/storm water very effectively by:

    1. Robbing incoming streams of momentum
    2. Allowing for uniformly sustained drainage
    3. Mitigating peak flow drainage
    4. Utilizing incoming streams for green purposes
  • Acoustics

    Acoustics of a building are areas that are usually paid least attention to while planning. They are often left to be dealt with when problems eventually arise, and the solutions – rubber padding, roof clads, plaster mats, vacuum mattresses – are neither cheap nor pleasant to look at. In fact, they turn the building into an eyesore with their obstructive appearances and bulky presence.

    Green roofs can, albeit unintentionally, work as great insulators of noise through the roof because of their dense packing and multi-layered structure.

  • Low Maintenance Benefits

    A green roof, due to above mentioned constructional benefits, invariably lengthens the strength and efficient life of the roof of the building. Roof renovation and maintenance activities are rendered less frequently necessary because of green roofs.[3]

Other Benefits of Green Roofs

Let’s briefly round up other miscellaneous benefits that green roofs bring to the property owners, residents and users.

  • Recreational Benefits of Green Roofs

    In increasingly urban areas of the United States – particularly in mega-cities like New York City and Chicago – having a bit of green around the house has become a luxury that costs thousands of dollars in the form of escalated property prices.

    In such conditions, green roofs can provide a much-needed green ambiance for homeowners and office employees. Simple recreational activities that would have been taken for granted a few decades ago like taking a stroll on a grassy patch of land have become rarities in such areas. Again, green roofs can provide an excellent solution in this respect.

    Reading, lounging and spending time with one’s loved ones atop such green roofs can be a great way to relax and truly, feel at home.

  • Health Benefits of Green Roofs

    There are quite a few passive ways in which green roofs can help home and property owners and/or residents.

    Having some greenery around the house has been researched and proven to influence residents in a palpably positive way. The American Psychological Association, after an extensive survey and research campaign, has found it to be true that having greenery around workplaces, residences and places of business can greatly and positively influence the psychological state of people working, living or visiting such places.

    In the same vein, it can be asserted that green roofs have tremendous potential to positively affect the state of mind of residents and users of buildings that house them.

  • Aesthetical Benefits of Green Roofs

    The easiest to perceive advantage of having a green roof is the fact that it can remarkably beautify the building roof – previously an empty and unused surface.

    Green roofs can add a touch of nature, even in the most densely built-up areas of cities. They can be easily altered and manipulated in terms of the variety of vegetation hosted, in order to change around the looks of the roof on a regular basis. Just like gardening, green roofs can provide a very good source of keeping busy for seniors and those who take active interest in gardening.

  • Business Benefits of Green Roofs

    For businesses and office complexes that choose to employ green house in order to bring vacant roof space into utility, the benefits of passive kind are many.

    Being green in operations is the need of the hour. It is a commonly observed phenomenon that almost all successful corporations seem to make conscious efforts to become green and let their consumers/customers know about it, as well. This has a passive impact on the customers, as it is likely that people would prefer a greener product/service over others. Hence, businesses can turn their operations a touch greener by implementation of green roofs so as to passively appeal such customers who are growing in numbers every passing year.

    In case of office complexes, green roofs can increases the efficiency and productivity of employees by presenting them with a natural and more pleasant ambiance.

Types of Green Roofing

So far, in this article, we have taken a look at what green roofs are, why they are beneficial, how they are beneficial and what makes them relevant, if not outright necessary, in this day and age.

Moving on, in this point, various types of green roofs will be discussed. It must be noted here that green roofs are, despite immense development in last few years, new phenomena to most people. Many are not even aware of the fact that green roofs are not just for businesses and corporations, but they can be implemented at houses, as well. Hence, categorization of green roofs is something that is done based on instincts and relevant industry practices. There is no rigid guide dictating how green roofs should be categorized or how they should be classified.

By popular consensus, however, green roofs are classified into three broad types, based on their reach, types of vegetation and level of indulgence.

[2] This can also be counted under the head ‘Financial Benefits of Green Roofs’.

  • Extensive Green Roofs
    A Typical Extensive Roof
    Figure 5: A Typical Extensive Roof (Image Credit: Reuters)

    Extensive green roofs are the commonest of all green roofs. They are often found on residential buildings, small community building, other small utility buildings like sheds, garages, warehouses and stables and miscellaneous roofs.

    Extensive green roofs are small-scale green roofs that cannot house large plant species. They are often used for growing area covering grasses, perennial flower plants and various small shrubs.

    Another characteristic of extensive green roofs is that they can be prepare off-site and transported to the site of use like grass turfs. They require very little to no maintenance at all, apart from regular irrigation. Extensive green roofs can provide two or three extra layers of insulation to the roof of the building, along with adding to the overall aesthetics of the building.

    It is a common practice to drop in extensive green roofs on already built roofs. They do not add much to the normal load on the roof (below 35 lbs per sq. ft. which is tolerable by most modern buildings) and hence, do not generally require a specific planning permission from local authorities. However, it is always the best idea to procure appropriate planning permissions before making any changes to the building that can potentially alter the structural stability and integrity of the building.

    Extensive green roofs are shallow in structure and rarely contain more than 5 layers of construction. Typically, extensive green roofs are less than 6 inches in thickness. They are designed to use the existing slope of the roof for drainage purposes, rather than optimizing the internal drainage layer/channels to ensure uniform moisture profile.

    The substrate/growth media used in extensive green roofs are neither specifically designed nor optimized for plant species. A layer of locally sourced soil that is moderately improved in nutrition by occasional feeding of fertilizers can act as a satisfactory substrate for the kind of plant species extensive green roofs are advised to host.

    Extensive green roofs are often installed or planted in various separated components or departments. These departments can be connected internally for drainage and aeration, however, they are not connected through substrate or root network. Compartmentalization of substrate allows the growth of various conflicting plant species without any ill-effect on the growth of vegetation.

  • Intensive Green Roofs
    A Large Scale Intensive Green Roof
    Figure 6: A Large Scale Intensive Green Roof (Image Credit: Zincoa Canada)

    Intensive green roofs are of grander and larger kind than extensive green roofs. They are often observed atop large commercial, public or office buildings. It is quite unlikely for one to be able to see an intensive green roof atop a residential building.

    Intensive green roofs are mainly designed in order to bring into utility vast expanses of vacant rooftops on commercial and public buildings such as factories, large warehouses, train stations, stadia, auditoriums, townhouses, churches, museums, schools, colleges and theaters.

    Intensive green roofs are pre-designed, meaning that they are not generally added into the existing structure as they carry considerably higher loads than extensive green roofs (to the tune of 100 to 150 lbs per sq. ft. or higher). Intensive green roofs cover vast expanses and hence, require various planning permissions from local authorities.

    Intensive green roofs are generally much thicker than extensive green roofs. Typical thickness hover around 15 inches, but it is not entirely uncommon to see intensive green roofs that boast of cumulative layer thickness to the order of 30 to 40 inches.

    Almost all garden plant species (except large trees and deep rooted, tall trees) can be hosted on intensive green roofs. They allow for a deeper proliferation of root network and hence, can house shrubs, bushes and bonsais. All flowering plants and vines can be successfully planted and grown on intensive green roofs. In that sense, an intensive green roof is not too different from a small scale garden. There have been precedents of owners installing park paraphernalia such as garden walkways, water fountains, benches and even small-scale playgrounds for children on intensive green roofs.

    Intensive green roofs require specialized, internally connected irrigation system that is clear and free of the original slope of the roof. This ensures that the drainage efficiency of the roof is not dependent on the original inclination of the roof. Aeration of roots can be a bigger worry when it comes to maintaining such a large scale of vegetation in a state of thriving. The problem of aeration is generally tackled through pumping of aerated water on a haphazard basis.

    The substrate used in intensive green roofs is generally not compartmentalized as it beats the purpose of creating a rooftop garden. Because of this, extreme caution needs to be observed while designing the substrate. Substrate used in generally locally sourced soil enriched highly by specialized minerals and fertilizers. In many cases, an on-site composting plant of small scale is also installed on the roof in order to further increase the greenness of the whole exercise.

    Because of the sheer scale of operations, intensive green roofs often require customized construction plans. For example, using more than one root control barriers is quite common in intensive green roofs. Similarly, multiple support layers are also used in many applications.

  • Semi-Intensive Green Roofs

    Semi-Intensive green roofs (sometimes also referred to as, semi-extensive green roofs) present a middle-ground between intensive and extensive green roofs.

    They are mostly used for aesthetics purposes and/or diversity and habitat promotion purposes. From small sized residential buildings to large sized commercial buildings, most buildings can host semi-intensive green roofs as they carry a lot of flexibility in terms of maintenance and cost.

    Semi-intensive green roofs generally entail a load of around 50 lbs per sq. ft. – a number that lies within the permissible load range of most buildings built in recent times. The average thickness of semi-intensive green roofs is around 5 to 8 inches and they are normally used for the plantation and growth of flowering plants, area covering grasses, Sedum genus of plants and perennials.

    The advantage of having a semi-intensive green roof in place is that they are highly customisable and can be used effectively in tandem with brown roofs.

  • Comparison of Green Roof Types

    Following table summarizes the three types of green roofs mentioned and discussed above.

Table 1: Comparison of Green Roof Types


Extensive Green Roofs

Intensive Green Roofs

Semi-Intensive Green Roofs


Less than 6 inches

15 to 40 inches

5 to 8 inches


Below 35 lbs per sq. ft.

100-150 lbs per sq. ft. (can be higher)

Around 50 lbs per sq. ft.

Primary purpose


Garden, recreation, environmental benefits

Aesthetics, bio-diversity, habitat conservation

Found commonly at

Residential buildings

Public, commercial buildings

Private and public buildings alike





Maintenance requirements




Irrigation requirements

Low (manual)

High (automated)

Moderate (usually automated)

Vegetation grown

Grass, small plants, perennials, succulents, drought plants, stonecrops

Shrubs, bushes, trees, grass, flowering plants

Perennials, Sedum genus plants, small shrubs, shallow root trees, succulents

Installing/Building a Green Roof

Green roofs have numerous advantages in environmental, ecological, financial and structural regards, as we have overviewed so far. Considering this slew of advantages, one would be inclined to think that installing or building green roofs must be a very expensive undertaking that would require a high degree of skilled labor operation for many hours. While it’s true that intensive green roofs do require such level of commitment and investment in terms of capital, time and labor, the same doesn’t really apply to extensive – or even, semi-intensive green roofs, for that matter.

This brings us to the next point in line for the discussions – installing/building a typical green roof.

A generic guide to building and installing an extensive green roof atop your house or office is described in a step-wise manner below.

  1. Consulting a Structural Engineer

    Before installing or building any sort of green roof, you need to consult a qualified structural engineer – preferably the one who had involvement in the design and construction of your house. Many people tend to ignore this fact and subject the very roof they live under to a grave and easily avoidable risk of failure.

    It must be understood that green roofs, however small in scale and size, do put a certain amount of load on the roof of your house. While most houses are designed to successfully carry such loads up to a certain limit, it is best advised not to test it out without the advice of an expert backing up your plans.

  2. Assessing the kind of green roof your house needs

    There are three main types of green roofs, as detailed in the previous point. Before trying to design or install a green roof atop your house, you need to understand in great details how these types compare against each other. While it’s true that most residential buildings will be best left to house extensive green roofs, there might be an odd chance that your house will be better suited to a semi-intensive green roof. Hence, understanding these finer points of differentiation (as noted in Table 1) can help you decide the type you want to go ahead with.

  3. Understanding costs

    Another obvious and widely asked question revolves around various costs involved in the process of designing, building, installing or just buying ready-to-install green roofs.

    It should be considered a rule of thumb that an extensive green roof of average substrate depth (say, 5 inches) will cost somewhere between $15 to $25 per sq. ft. The cost mentioned here is only indicative and can vary to a certain extent depending upon the variation in variables like commodity prices and special requirements.

    Root blockers and waterproofing membranes are two components of a green roof that contribute the most to the total cost. Hence, understanding these costs is of essence while building, installing or buying extensive green roofs.

  4. Choosing the right plants

    The next step involves selecting the right species of plants for the green roof. For extensive green roofs, plant species to be used are generally expected to meet the following criteria: 

    1. They are required to have shallow growth.
    2. They should not have deep root network.
    3. They should be able to thrive even with irregular irrigation.
    4. They should have wider growth.
    5. They should not weigh too much.
    6. They should be easy to maintain.
    7. They should be attractive in appearances. 

    Considering these criteria, regular flowering plants, vegetables, grass, sod, Sedum genus plants, stonecrops etc. are the usual suspects for green roofs.

  5. Building the frame for a green roof

    One aspect of a green roof’s structure that was deliberately not discussed in the earlier part of this article when the cross section of a green roof was explained in details is the frame of a component, or a sidewall.

    Sidewall of a green roof can be made either of strong wood or PVC material. The sidewall should be thick enough to sustain the whole assembly and the lateral pressure it exerts. By measuring the available space, sidewalls can be cut out of strong wood and then waterproofed with regular oil paint or turpentine for longevity.

  6. Choosing the base layers

    The base layers of a green roof are important structural parts of it as they are difficult to service once installed. It’s a common practice to buy ready-made base layers (vapor control layer, support layer, root blockers and drainage layer).

    The root blocking layer and the membrane layer can be designed to order based on requirements. Many manufacturers specialize in durable and affordable membrane layers for extensive green roofs.

  7. Choosing the substrate

    Choosing the substrate for extensive green roofs is usually a straightforward process. In most cases, locally sourced soil is enriched with a moderate dose of fertilizers and external minerals to create a nutritious organic substrate.

  8. Designing the green roof

    The design of a green roof is largely dictated by three factors:

    • Availability of space
    • Chief purpose of the green roof
    • Present state of the rooftop (age, load capacity, slope etc.)

    Depending upon these factors, appropriate designs can be made for the green roof. For small scale household green roofs, any suitable design that doesn’t obviously defy logic is good enough. For moderate or large scale green roofs, assistance from professionals should always be sought.

    The steps in the installation process of a green roof can be summarized as:

    1. Place a rigid PVC or HDPE surface for support at the location.
    2. Cover it with a layer of waterproofing membrane.
    3. Place a thin and sloped layer of drainage material (gravels, sand etc.)
    4. Top it off with a root blocker mesh.
    5. Internal aeration channels can be installed for larger roofs.
    6. A layer of substrate (growth media) is to be placed on top of the root blocker mesh.
    7. The substrate layer is to be levelled horizontally and then planted with vegetation.

Green Roofs: Sustainability and Maintenance

One of the most attractive factors that pushes building owners and businesses to opt for green roofs is the fact that green roofs are inherently sustainable, for the best part of their existence. That having said, green roofs are not without their needs for regular maintenance, like most useful things. In this point, we will try to take an overview of the sustainability and maintenance of green roofs.

Sustainability of Green Roofs

Green roofs, owing to the fact that they are green in existence and operation, are inherently sustainable. Most of these points of sustainability have already been covered earlier in this article under the head ‘Environmental Benefits of Green Roofs’. Hence, a quick rundown of these points will suffice at this juncture.

  • Air Quality

    Green roofs improve air quality around their existence by trapping toxic gases, absorbing carbon dioxide and adsorbing various pollutants.

  • Improved Rain/Storm Water Management

    Green roofs reduce erosion of buildings caused by rain/storm water. They also reduce drainage by up to 50%. Runoff streams are greatly enhanced in quality, as they are free of dirt and pollutants

  • Saving Energy

    Green roofs act as efficient insulators of heat. During winters, indoor heat is prevented from escaping through the roof via conduction, convection and/or radiation because of this insulation provided by green roofs. This effect is estimated to help buildings consume up to 25% lesser electricity for heating.

  • Helping the Biosphere

    Green roofs are great hosts of local habitat and can be used to allow local species of plants and various organisms thrive in familiar conditions. Green roofs can bring back a touch of much needed greenery back to our cities.

  • Economic Sustainability

    In terms of economics, green roofs are sustainable, albeit only over long terms. They should, however, not be looked at financial investments as a host of other benefits they entail more or less make them intrinsically sustainable in the economic sense.

Maintenance of Green Roofs

Another very commonly asked question about green roofs revolves around the level of maintenance they are supposed to require. While it’s really difficult to quantify the level of maintenance that a green roof may need over time, there are certain factors that we can discuss to get close to this notion.

Before doing that, however, answering another tangential question is necessary. As many manufacturers and installers advertise, a lot of building owners are lured in by the words ‘no maintenance’. It should always be remembered that a green roof is not a machine, but it’s a natural, living habitat. It’s called a ‘living roof’ for a reason. Hence, it would be really undue to expect this micro-habitat to not require any sort of maintenance whatsoever for healthy existence. That’s why, if you are a building owner or a business probing the possibility of installing or building a green roof, you should always take the fact that green roofs do require maintenance in your stride.

Intensive green roofs are often handled by professionals who are experts in building and maintaining green roofs. However, when it comes to extensive or semi-intensive green roofs, owners seem to be at a loss regarding how exactly to go about it. Many try to maintain green roofs the same way that they would maintain a garden, a mistake that often results with the roof being left in a disarray.

Following major maintenance points will help building owners take better care of their green roofs.

  • Scheduling is the key!

    While maintaining a green roof of any type, scheduling of good precision is the real key. All maintenance activities that will be discussed below are only effective when implemented in a scheduled and timely manner.

  • Maintaining the substrate

    The substrate, or the growth media, will have direct impact on the state of health of the vegetation being grown. Maintaining the substrate on a regular (weekly or bi-weekly) basis is important. Following activities should be taken up in order to ensure a healthy state of the substrate:

    1. Aeration via internal channelling should be ensured. If that’s not possible, regular roughing up and rolling over of substrate layers can be satisfactory enough.
    2. Weeds and other unwanted plants that inadvertently come about should be removed regularly as they sap valuable nutrients.
    3. Fertilizers and mineral should be used on a sporadic (monthly or semi-annually) basis to enrich the substrate. After a period of about 18 months, substrate should be replaced.
    4. Substrate should be checked semi-annually for quality in soil laboratories. 
  • Maintaining the vegetation

    Maintaining the vegetation can be the easiest part of the whole maintenance cycle. Following points should be considered as guidelines to keep the vegetation in a well maintained state of existence and growth.

    1. Vegetation should be checked regularly for signs of fungal or yeast infection. If found, such infections should be treated with appropriate fungicides as recommended by experts.
    2. For plants and bushes and that can grow unchecked, a regular trimming of leaves is necessary. Same applies for grass. 
  • Maintaining the Irrigation 

    This is the most challenging aspect of the maintenance of a green roof. In most cases, drip irrigation is the best course of action for green roofs. If the roof is extensive in nature and very small in area, manual irrigation can be just as effective.

    In most parts of the United States, soil (without additives) has a moisture retention period of 10 to 15 days. This means that an effective irrigation cycle should have a frequency of no more than two weeks. Weekly irrigation works well with the Sedum genus of plants (described earlier) as they are classified as drought plants. For area covering grasses, moisture requirements can be higher. Hence, in such cases, maintaining the moisture in the substrate every two to three days is necessary as well as sufficient.

  • Maintenance during Winters

    Green roofs are prevalent in places where winters are harsh and long. What, then, should be the strategy for the maintenance of a green roof during winters? It’s quite common for green roof owners to either shift sizeable vegetation (plants, not grass) indoors during winters. If that is not a practical feasibility, it is best advised to remove the vegetation just as the winter sets in and start afresh after the winter concludes. Leaving the plants as they are can also be effective, especially as it adds another layer of insulation – a great asset to have during winters.


Slate Roofing

Slate roofing, in the American context, is a very traditional type of roofing. Found extensively in East Coastal and Southern towns of the country, slate roofs provide the house with a certain vintage look that many homeowners seem to savor for the sake of nostalgia. However, nostalgia is not the only reason why slates are still the in-thing when it comes to roofing. There are many other associated advantages, as well.

What are slates?

Slates are, contrary to popular opinion, not manufactured. They are natural sedimentation rocks found in shallow sea-beds all across the East Coasts of the United States. They are metamorphic rocks that are strong yet a tad brittle. They are multi-layered and are formed over thousands of years as the water pressure pressurizes sedimentation layers together in a dense structure (not unlike layers of an onion).

What makes slate rocks particularly attractive in the roofing sense is the fact that they can be cut to precision using special tools by simply fracturing them normal to the angle of their layers. There are two axes of fracture to all slate rocks – along the grain and along the perpendicular. This allows one to fabricate uniform batches of slate tiles with no internal fractures.

Slates are found in many countries, most notably Japan, Brazil, China, Australia and the United States. In the United States, slates are predominantly found in Maine, Vermont, Massachusetts, Connecticut, parts of Pennsylvania, Georgia and North & South Carolina. In Canada, Newfoundland is a prominent slate producing state.

Slate Roofing

Slate roofing is a conventional method of roofing (predominantly sloping roof). Uniform slate tiles are interlocked and/or interspersed with precision in order to create a mat-like pattern that efficiently and effectively covers the area of the roof. The best feature of slate roofing is that it is very attractive and does not take more than a few hours for small and medium sized roofs (less than 2,000 sq. ft.).

Attractive Slate Roofing
Figure 7: Attractive Slate Roofing (Image Credit:

Slates have been used for hundreds of years all over the world (especially in coastal areas) for roofing.

Pros and Cons of Slate Roofing

The very fact that slate roofing has been in practice for centuries is good enough to know that the pros of slate roofing far outweigh the cons of the same.

Let’s take a look at the prominent pros and cons of slate roofing.

Pros of Slate Roofing

  • Aesthetics The most prominent advantage of using slates for roofing is that slate roofs have a certain naturally pleasant demeanor to them. A slate roof can render the entire building more attractive with the natural beauty of slates. Slates are often associated with grandeur and that helps in this respect, too.

  • Durability Slates are far more durable than their counterparts (brick shingles, rock shingles, wooden roofs etc.). It is a common sight for us to observe slate roofs on historical buildings, monuments, churches, town houses and museums. In fact, most slate roof fabricators do provide a natural life warranty (notwithstanding destruction by disasters) of 100 years or more.

  • Weatherproof Slate is a rock that has already undergone the harshest of climatic conditions imaginable for thousands of years. These conditions render slate rocks with a characteristically dense structure that is completely waterproof. Slate doesn’t absorb a single drop of water, and hence, can easily withstand rain and snow, without allowing for any seepage whatsoever. Moreover, slate can resist a high temperature gradient, meaning that a high difference in indoor and outdoor temperatures won’t cause slate to contract or expand to the point of breaking, because slate is a very poor conductor of heat. Slate rocks are fire-proof and shock-proof. Hence, they can easily sustain indoor fires, extreme heats and occasional impacts.

  • Low on Maintenance Slate rocks are markedly low on maintenance. Once installed, slate roofing does not require much in the way of maintenance, apart from occasional inspections, washing cycles and collected debris (leaves, dust etc.) removal. 

  • Slates are GreenUnlike many other roofing materials, slate roofs are 100% natural in origin. They are not processed at all, apart from cutting and installing operations. They can last for decades and being natural, do not pose any harm to environment. In fact, using slates is akin to avoiding precious landfill space that would otherwise be used up by alternative roofing materials. 

  • Property Value Addition Because of the all the advantages listed above, an automatic advantage that follows is that a slate roofing can significantly increase the real estate value of a building.

The value addition has, in part, to do with the attractiveness that slate roofing imparts to the building, as well as its durability and longevity.

Cons of Slate Roofing

  • Weight and Stress Slates are highly dense sedimentation rocks. Because of this, they are also quite heavy. A typical slate roof is estimated to exert a load of around 1,000 to 1,500 lbs per sq. ft. on the building in the normal direction. This load is generally higher than what other alternative roofing materials exert. Hence, buildings with sufficient load bearing capacities are the only ones who can house a slate roof. Old constructions are usually advised against having a slate roof for the same reason.

  • Installation Difficulties For an expert slater[4], installing a slate roof may not be a job that entails much complications. However, if not done properly, a slate roof can quickly unravel in efficiency, leaving much more work to be done as maintenance.

  • Expensive Slate roofing is one of the costliest roofing options you can hope to find in America. A regular sea-bed slate roof can cost to the tune of $1,000 per sq. ft. Adding transportation and installation costs to it, building owners can expect to pay at least $1,200 per sq. ft. for a quality slate roofing.

Types of Slate Roofing

Slates used in roofing are commonly classified according to the most obvious of criteria – their color. Besides that, slate roofing (not slates themselves) can be classified into three broad categories:

  • Uniform Slate Roofing Uniform slate roofing, as the name suggests, uses slates of even sizes, colors, textures and patterns to create a highly structured and ordered look. Uniform slate roofing is often used in places of business and public buildings like churches and schools.

  • Graduated Slate Roofing Graduated slate roofing, for the better part of it, is just like uniform slate roofing. However, it is different in the sense that it employs varying sizes of slates at different parts of the roofs. For example, a graduated slate roof will commonly have thicker and stronger slates at the eaves and at the beams, while relatively thinner slates will occupy the body and the top of the roof.

  • Random/Uneven Slate Roofing In random/uneven slate roofing, slates of varying sizes, patterns, colors and styles are employed in a single roof creating a very attractive abstract pattern. Such roofing can be observed in modern buildings that use slate roofing.

  • Types of Slates Following table (table 2) sums up various types of slates widely used in the United States.

[4] It is a common practice to refer to a slater roofing specialist as a slater

Various Types of Slates Found in the United States
Table 2: Various Types of Slates Found in the United States

Installing a Slate Roof

Installing a slate roof is not something that most people would be advised to undertake by themselves, especially if they are not trained in handling and operating various equipment that would be needed. In addition, installing a slate roof means climbing up to heights, and hence, people who are not comfortable at heights should refrain from undertaking such exercises.

In addition, slate roofing tiles are generally expensive. Hence, proper care needs to be taken while installing a slate roof. A very rough guideline to install a slate roofing, for those who are interested, is presented below.

  1. Measure the roof area accurately and then calculate the number of standard tiles (12’’x 10”, 10”x8”, 16×12” etc.) that will be needed.
  2. Buy appropriate number of styles with appropriate thickness. Consulting a structural engineer before buying slates is recommended.
  3. Arrange the tiles on the ground in the same pattern that you have envisaged for the roof.
  4. Drill holes into all tiles (if they are not already drilled).
  5. Affix each tile to the roof with the help of nuts, bolts and gaskets provided with tiles.
  6. Make sure that all tiles are firmly fixed to the roof and they interlock with perfection.
  7. Corner tiles and eave tiles can be installed before body tiles to get an idea of how the structure would look.
  8. You might need to cut some tiles to fit them in the available space.

Sustainability and Maintenance of Slate Roofing

Slate roofs are self-sustainable for decades. As noted earlier, most fabricators furnish a warranty of at least 100 years for slate tiles. This makes slate roofs eco-friendly as durability equates to greenness. Furthermore, slate tiles are just natural rock plates, and hence, do not pose any threat to the environment.

As far as maintenance is concerned, slate roofing requires very less of it, as well. That said, there are certain maintenance aspects that can ensure that slate tiles actually last for decades.

  1. Regular inspection is the key here. A thorough inspection of the roof on a regular basis (say, once every three months), can reveal any flaws, if present. These can then be remedied before they grow in gravity.
  2. Cleaning of a slate roof is important for its longevity. Rotting organic matter on the roof can give rise to fungal infestation that not only looks unpleasant, but also structurally hampers the roofing.
  3. Getting rid of water stagnancy points is important for the same reason, as well (despite the fact that slates do not absorb water).
  4. During winters, special care should be provided to a slate roof. The only natural factor that can have detrimental effect on slates is cold. Hence, it should be ensured that there is no prolonged collection of snow on tiles. 

Bitumen Roofing

Modified Bitumen Roofing
Figure 8: Modified Bitumen Roofing (Image Credit: Alpine Roofing Co.)

Bitumen roofing (also known as modified bitumen roofing) is a popular roofing option in many countries around the world, including the United States. Bitumen roofs are still relatively newer and their widespread adoption cannot be traced back to more than 50 years ago.

What is a bitumen roofing?

Bitumen roofing is a standard form of membrane roofing in which a membrane of modified and processed bitumen is used as the exposed part of the roof, along with various base layers such as support layer, surfacing layer, adhesive layer, waterproofing layer and insulation layer. A modified bitumen roof is low in cost and maintenance and can easily provide a satisfactory active life of 50 years or so. Bitumen roofing is, furthermore, very cheap in comparison with other options as one would be required to pay less than $15 per sq. ft. of the roof for materials as well as installation.

Bitumen roofing, in functionality and construction, is just like any other membrane roofing like a PVC roofing or a metal roofing.

Pros and Cons of Bitumen Roofing

Various pros and cons of bitumen roofing are mentioned below in order to allow readers to have an idea about whether a bitumen roofing is a good option for their own houses.

Pros of Bitumen Roofing

  • Low Cost Bitumen roofing is extremely cost-effective because it costs a fraction of what other roofing options do, and still provides long, durable functionality.
  • Winter Effective Bitumen roofing has another massive edge over alternative roofing strategies in that bitumen membranes are extremely pliable. They do not stiffen up even during the harshest and longest of winters, meaning that you won’t be required to replace them just as the winter passes by.
  • Easy Installation Installation of a bitumen roof is very easy and quick. It only involves pasting the membrane onto base layers. Even large areas of a roof can be covered in a day’s work.

Cons of Bitumen Roofing

  • Not So Green Bitumen is a natural pseudo-polymer that is often processed before using as a roofing membrane. It does not decompose naturally and hence, is not quite eco-friendly in the long run. 
  • Fire Hazards Bitumen is an inflammable substance (a distant form of amorphous coal) and therefore, presents the roof with vulnerability to fire hazards. 

Installing a Bitumen Roof

Installation of a bitumen roof, though easy, should be approached with care as it involves health and fire hazards.

  1. The very first step is to procure base layers (bound in one) and the bitumen membrane.
  2. The next step is to clean your roof thoroughly by washing and scrubbing.
  3. After scrubbing, the roof needs to be torched heavily with the help of a propane lighter before applying the base layer bundle. You will need help from one or two fire-safety trained assistants for this task.
  4. One adequately hot (locally), the base layer bundle can be affixed onto the roof.
  5. As the base layer bundle gets cured (it takes two to three hours), you can easily paste the bitumen membrane sheet onto it. Further curing of about five to six hours will ready the bitumen roofing for all weather conditions!

Sustainability and Maintenance of a Bitumen Roof

Bitumen roofs are not really environmentally sustainable in the long run as they are made of processed asphalt and quarried bitumen. Hence, from the ecological point of view, their sustainability is poor. However, bitumen roofs tend to reflect sunlight, meaning that indoor temperatures are controlled during summers. This reduces the load on air conditioners, allowing them to consume lesser electricity. This is perhaps the only sustainable aspect of a bitumen roof.

Regarding the maintenance, regular maintenance cycle and thorough inspection are adequate.

Following things can be used as a checklist of sorts:

  1. Checking for curling edges
  2. Checking for tears, rips and fades
  3. Checking for nuts, bolts, gaskets, joints and welds
  4. Checking for adhesive unity and creases
  5. Checking for air intrusions

Roofing Shingles

When the word roofing is referred, it is the image of a roofing shingle that greets the eye of most people, and quite rightly so. Roofing shingles are the most commonly used components of innumerable roofing techniques, throughout history, all over the world.

Roofing Shingles: What are they?

Roofing shingles are flat, often curved tiles built from a variety of materials that can be locked together to create a closely knit pattern that covers the entire area of a roof. Roofing shingles are often used on sloping roofs and they channel rain/storm water through their interlocking pattern, without allowing for any seepage.

Some of the popular materials that roofing shingles are often made of are listed below:

  • Wood
  • Slate
  • Asphalt
  • Concrete
  • Cement
  • Polymers
  • Ceramic
  • Rubber
  • Metal

How Roofing Shingles Work

Roofing shingles are arranged in such a way that the bottom edge (eave) of every shingle covers the top edge (neck) of the shingle that follows it down the slope. The intricate pattern that is created is good enough to make the entire assembly watertight. Channelling creases present strategically on every shingle allow for any water cast on the shingle to run down the slope easily, without causing any sort of erosion.

Pros and Cons of Roofing Shingles

Roofing shingles have many advantages when it comes to easy and efficient use of available resources. There are, quite understandably, some cons associated with them, as well. Let’s overview the pros and cons of roofing shingles.

Pros of Roofing Shingles

  • They are lightweight, and most buildings can support them without additional strengthening.
  • They are weatherproof to a high degree.
  • They are cheap and easy to procure.
  • They are easy to install, maintain and replace.
  • They are inconspicuous in appearances.

Cons of Roofing Shingles

  • They are not as durable as slates.
  • They can get displaced during high wind or storm.
  • They do not add much to the beauty of the building.
  • They need to be serviced more frequently than slates.

Types of Roofing Shingles

There are far too many types of roofing shingles in existence and practice to mention. This has primarily to do with the fact that various people in various parts of the world have taken up the concept of shingles and modified it to suit their own requirements and resources.

Some of the commonest of these are noted below.

  • Wood Shingles Perhaps the oldest type of roofing shingles, wood shingles are still used in places where wood logging is easy and prevalent. Wood shingles are easy to procure, design, cut, install and replace. Depending upon the wood used and the level of processing, wood shingles can provide a life cycle of 25 years or more. Cedar, pine, spruce and oak are some of the common types of wood that are used for making shingles.Wood shingles are definitely the most attractive type of roofing shingles, and hence, the most expensive one, too.
  • Asphalt Shingles Another very prevalent type of roofing shingles is asphalt shingles. Found almost everywhere, irrespective of climatic conditions, asphalt shingles are cheap, easy to install and easier to replace.Even though they do not offer an active life of more than 30 years on an average, they are still cost-effective in the long run.
  • Metal Shingles Metal shingles are customary in the coastal towns of the United States. They are, however, gaining traction in other parts – especially the Midwest – too, in recent years.Metal shingles are generally lightweight metal (galvanized steel) casings that are weatherproofed by further coats of paint. Metal shingles are available in the form of tiles and can be installed in a matter of hours. They are expected to serve the roof for 50 years, on an average.

Apart from these three major types, there are other popular types like stone shingles, slate shingles, rubber shingles and PVC shingles.

Installing Roofing Shingles

Installing roofing shingles is relatively easy if you are well-familiar with the structure of the roof of your house and how shingles are supposed to interlock. A brief guide to installing roofing shingles is given below.

These steps should be used only as guidelines, and assistance from professional quarters while installing roofing shingles is always best advised.

  1. As the very first step, you will be required to clear the roof of all collected debris. Scrubbing it to thoroughly clean it is highly recommended.
  2. Before getting on with the shingles, you will need to inspect flashings, eaves, fascia (if any), chimney joints and other structurally weak points. If they need maintenance or repair, it should be taken up before installing shingles.
  3. You will be required to have a design pattern (if at all) ready to guide you before installing shingles on the roof. According to the design pattern, you can then arrange shingles on the roof to be bolted firmly in place.
  4. Before installing the body of the roof, it is a good idea to install eave and ridge shingles. Once that part is dealt with, you can proceed to carefully install the body shingles with proper interlocking to leave no space in between.
  5. You may choose to caulk the space between shingles with a caulking gun, but it’s generally not necessary.

Sustainability and Maintenance of Roofing Shingles

As far as sustainability is concerned, roofing shingles are neutral in most cases (apart from rubber and asphalt shingles). They serve their life cycle fully well and then can either be landfilled or recycled with relative ease. Shingles help in insulating the roof, as well as managing the rainwater runoff with higher efficiency.

Maintaining roofing shingles is not a difficult task either. Here are some quick points to help you intensify your roofing shingles maintenance schedule:

  1. Always make sure to clean out roofing shingles of debris and dust so that there is not accumulation that can lead to fungal infestation.
  2. At least thrice a year, a thorough inspection of roofing shingles for breakage, damage, distortion and position should be carried out. Such inspections are quite necessary after a sustained spell of rain, snow and/or storm.
  3. If you find that one or more shingle tabs are damaged for whatever reason, it’s quite easy to unbolt them and put new tabs in place.
  4. All caulking jobs and sealed spots should be re-caulked and re-sealed every two months to ensure their efficiency in blocking moisture.

EPDM Rubber Roofing

Rubber Roofing on a House
Figure 10: Rubber Roofing on a House (Image Credit: YouTube)

EPDM rubber roofing has, in a quick period of time, become one of the most popular roofing methods used in the United States.

EPDM (ethylene propylene diene-terpolymer) is a special polymeric substance derived from heavy oil residues and recycled rubber tires. EPDM is hard, pliable, weatherproof and does not disintegrate naturally – properties that make it an ideal choice for roofing.

There are two main ways in which EPDM rubber roofing can be used to top-off building roofs.

  • Rubber Shingles Rubber shingles are chiefly made from recycled rubber from discarded vehicle tires. Installation and maintenance of rubber shingles is just like that of other roofing shingles discussed in the previous point of this article. The only difference lies in the fact that rubber shingles are often glued to the roof with elastic industrial adhesive, and not bolted to the roof.
  • Rubber Roof Mats/Rolls This is perhaps the modern day variant of shingles, used primarily on roofs of no or little natural slope. Rubber roofing mats are ready-to-roll rubber mattings that can be adhered, glued or ballasted to the roof using industrial adhesives.

Pros and Cons of Rubber Roofing

Relative advantages and disadvantages of having a rubber roofing instead of other options are discussed in brief below:

Pros of Roofing Shingles

  • Rubber roofing uses many discarded tires through recycle. This makes them eco-friendly. It is estimated that every square foot of rubber roofing helps get rid of at least 5 discarded car tires.
  • Rubber roofing is cheap and easy to install.
  • It provides a cost-effective option, as a rubber roofing is expected to last 50 to 70 years from installation.
  • Installation does not require expertise.
  • Rubber roofs are low on maintenance and can be replaced easily.
  • Rubber roofs are weatherproof and provide good insulation – especially in places where average year-round temperatures are on the lower side.

Cons of Roofing Shingles

  • Rubber roofing is susceptible to fire hazard, just like bitumen roofing.[5]
  • Rubber roofing does not provide good stabilization of thermal gradient in places where average annual temperatures are on the higher side.
  • Rubber roofing can get torn by accidental falls of tree branches or during hailstorm.
  • Rubber roofing does not contribute much in way of beauty or attractiveness to the outlook of a building.

Types of Rubber Roofing

There are three major types of rubber roofing, viz. fully adhered, loosely laid and fastened rubber roofing.

  1. Fully Adhered Rubber Roofing Fully adhered rubber roofing is the type that is most widely used because it provides flexibility of installation. Such roofing is adhered to the insulation base layer using high strength industrial glue that does not give in, even during the harshest of climates. A fully adhered rubber roofing can be expected to provide a service life of at least 50 years. It is best suitable for roofs with irregular slopes and contours (protrusions, troughs etc.). A special layer of non-permeable insulation membrane can be used to reinforce the temperature performance of the roofing.
  2. Loosely Laid Rubber Roofing A loosely laid rubber roofing is also known as a ballasted rubber roofing. It is generally used on rooftops that are large in areas. A ballasted rubber roofing is heavier and there is no mechanism other than the dead weight of the roofing material to keep it in place. A ballast rubber roofing is often found on warehouses and factories.
  3. Fastened Rubber Roofing A fastened rubber roofing is not much different than a fully adhered rubber roofing. The only difference lies in the way the roofing material is bound to the roof. In case of a fastened rubber roofing, mechanical means of attachment like rivets, plates, fasteners and gaskets are used to affix the roofing material firmly to the roof.A fastened rubber roofing can be expected to provide an active service life of at least 35 years. It, however, needs the highest degree of maintenance among all rubber roofing types, as attachments tend to wear or come off in the course of time.

Installing a Rubber Roof

A quick step-by-step guide to installing a rubber roofing (mechanically fastened) is given below.

  1. Just like before installing any type of roofing, the roof needs to be cleared out and scrubbed to get rid of all debris.
  2. A 3 or 4 mm plywood board is often used as a base layer for rubber roofing. This board, in composites, can be attached to the roof with the help of nuts and bolts.
  3. Once the roof is entirely covered with the base material, insulation layer (present with the roofing material) can be glued to it using any industrial strength hot glue.
  4. Thereafter, the roofing material can be spread and affixed atop the insulation layer (after de-creasing) using mechanical fasteners (a combination of rivets and gaskets).
  5. Care should be taken to not tear the roofing material, as once torn, the entire patch (10 to 50 sq. ft.) of the material becomes useless.

Sustainability and Maintenance of a Rubber Roof

It is really difficult to judge the sustainability of a rubber roof. The fact that most EPDM rubber roofing mats and shingles are made out of recycled rubber from tires makes them quite eco-friendly. However, another fact that they are themselves just as difficult to get rid of nullifies that positive effect.

Regarding maintenance, there’s not much required in case of a rubber roofing. Following points will help you look after a rubber roof and perhaps, extend its service life.

  • Inspecting the roofing on a regular basis (at least once a month) is very important.
  • Rubber roofs should be regularly (twice a month) cleaned to get rid of all collected dust, debris and plant matter that can eventually rot and give rise to a number of associated problems like pests and fungal infestations.
  • In case of mechanically fastened rubber roofs, special inspection of fastening means (rivets and gaskets) should be carried out on a regular basis. These fasteners, even though they are generally rust-proof and chrome plated, tend to weaken due to incessant exposure to the outdoor air.
  • Over a period of time (say every five years), rubber roofing material tends to come loose and allow for air to infiltrate the roofing material-insulation layer conjunction. Hence, complete de-creasing using special hot irons is required to tackle creases.
  • Cleaning a rubber roof, on the other hand, is a very easy job. Any mild detergent and cotton washcloth can suffice to clean a regular rubber roofing with ease and efficiency. Use of hot water and caustic detergents is strictly prohibited on rubber roofing materials.
  • One very important thing that needs to be mentioned here is that when you observer the presence of slight wear and tear on rubber roofing, do not ever try to conceal or remedy it using duct tapes. Duct tapes are common reasons why rubber roofing comes off the base layer. Wear and tear should always be treated with an insulation paint coat or a rubber paint coat. Pasting a single rubber shingle can also be another good remedy in such cases.

[5] Modern EPDM roofs are fire-resistant. However, they are costlier than the normal variant.

Ice Dam on a Roof

Ice Dam formed on a roof in rural Minnesota
Figure 11: Ice Dam formed on a roof in rural Minnesota (Image Credit: Heritage Lane Builders)

Ice dams on roofs can be observed very commonly in places where average annual temperatures are on the lower side, and winters are long and harsh. Ice dams, if not treated properly in due time, can cause immense damage to the roof, as well as the structural integrity of the building.

What are Ice Dams?

Ice dams, to put it very simply, are sizeable ridges or levees of ice that are normally formed at the edge of a sloping roof, or on the eaves. Ice dams, once formed, can cause a load of water to remain stagnant on the roof.

What causes Ice Dams on Roofs?

A number of factors need to come together for an ice dam to form on the roof. These factors, however, are very common and hence, ice dams are common phenomena in cold regions.

Here’s how these factors combine together to form an ice dam:

How an Ice Dam gets formed
Figure 12: How an Ice Dam gets formed (Image Credit:
  1. There are three most essential prerequisites for the formation of an ice dam: a sloping roof, temperature below freezing and warmer indoor conditions, particularly attics and stairways.
  2. As the temperature falls below the point of freezing, snow falls and over time, snow gets accumulated on top of the roof.
  3. If everything went to the plan, one would expect this snow to melt gradually, turn into water, flow down the sloping roof into the gutters and drain off. However, when there are sustained periods of cold, snow doesn’t melt naturally.
  4. But in occupied homes, indoor conditions are warmer, keeping the base layer of the roofing warmer. This heat melts the base of accumulated snow and it flows down the roof.
  5. However, at the eaves or at the protruding edges of the roof, there is no indoor heat gradient present. So the runoff stream gradually freezes again, forming a mass of ice at the edges.
  6. Over time, this mass goes into size and forms a dam like structure.
  7. The indoor heat keeps melting a part of accumulated snow. However, because of the ice dam, this runoff stream cannot reach the gutters. This forms a pool of water on the roof.
  8. This pool of water often seeps into the roof, causing fungal infestation, structural weakening and unnecessary dampening of building walls.

How to Remove an Ice Dam?

An ice dam can be remove by breaking the ice ridge formed at the edges of the roof using metal tools. Clearing downspouts is also necessary while removing ice ridges. However, merely breaking the ridge is of no use, as it will form again in no time. Permanent solutions (noted below) must be implemented to avoid recurrence.

How to Prevent Ice Dams from Forming?

Removing ice dam is just a quick solution. To prevent ice dams from forming altogether (or at least, minimizing their damage potential), there need to be made some indoor changes, rather than outdoor ones.

The very first area to address is attic temperature. By reinforcing attic insulation, you can prevent heat from losing to the roof, thereby preventing the melting of snow. Improving attic ventilation can also achieve the same objective.

Another preventive measure is to regularly clean out snow accumulation at eaves and edges of the roof.


Metal Roofing

Metal Roofing
Figure 13: Metal Roofing (Image Credit:

Coming back to various types of roofing, metal roofing cannot escape a mention here. It is estimated that over 10% of all residential as well as commercial buildings in the United States boast of metal roofs of various types and sizes.

Metal roofs have never been first-choice roofing in America. However, as more and more people have come to realize the cost-effectiveness of metal roofing despite their high initial costs, there has been a significant rise in their popularity as a premium roofing type.

An out-and-out metal roofing can be quite costly for a residential building. The first recorded mention of a metal being used for roofing purposes can be found as much as 1,500 years back in time, in Asia. Copper sheets, copper plates and copper coated wooden shingles have been common roofing materials in China and Japan for centuries. Even today, corrugated steel and tin are extensively used in many parts of the developing world, most notably in South Asia and Africa.

In the United States, metal roofing is mostly used to reinforce the roof in terms of aesthetics, insulation and weather-protection.

Which Metals are used for roofing?

Stainless steel is the most commonly used metal (an alloy, technically oofing purposes. Other than steel, copper, aluminium, tin and various alloys are used depending upon requirements.

Pros and Cons of Metal Roofing

Relative pros and cons of metal roofing are listed below.

Pros of Metal Roofing

  • Metal roofing can provide excellent stability to the roof.
  • Metal roofing is generally made of entirely recycled metal scrap, making it eco-positive. Furthermore, it doesn’t diminish much in value, even after years of service.
  • Metal roofs are much more durable than asphalt shingles and other common roofing types. A typical metal roof will last for over 50 years, as opposed to the 20-30 year service of an asphalt roof.
  • Metal roofs can provide great insulation against cold.
  • Metal roofs help a building consume a lot less electricity. Hence, metal roofs are profitable in the long run.

Cons of Metal Roofing

  • Metal roofing involves significant initial capital investment. This is probably the single most disadvantage that prevents many building owners from installing metal roofs.
  • Metal roofs are, because of their value, susceptible to thefts.
  • Metal roofs can rust in the long run, diminishing in functionality and value.

Sustainability and Maintenance of Metal Roofing

Metal roofs, apart from the energy that mining and fabricating processed consume, are relatively eco-positive. Furthermore, most metal roofing units are fabricated from 100% recycled metal scrap. Metal roofs have high reuse value, as well – making them very sustainable.

From the maintenance point of view, there are some rudimentary precautions that can easily extend the life cycle of a metal roofing. These are:

  1. Metal roofs are highly susceptible to rusting. Hence, it should be made a point that they are, very regularly, coated/painted properly to avoid the natural oxidation process.
  2. Metal roofs can, very rarely, show signs of local failures like wear and tear, thinning, chipping and even disintegration. When such signs are visible, qualified metal workers should be hired to remedy the problem.
  3. Checking seams, joints, welds and holding glands at least once every two months can ensure that the roof is in a solid position, structurally.

Flat Roofing

Flat roofing is a very common type of roofing in which the entire roof does not have a significant slope. If the slope of the roof is less than 10 degrees at every edge, the roof is generally said to be a flat roof. Flat roofs are mostly built in areas where it does not rain or snow much.

Pros and Cons of Flat Roofing

Following points sum up the major pros and cons of a flat roof.

Pros of a Flat Roof

  • A flat roof is easier to construct.
  • It can be doubled up as space for occupation, or for green roofing. 

Cons of a Flat Roof

  • Because it doesn’t have significant slope, a flat roof shows poor drainage characteristics.
  • This also means that a flat roof is high on maintenance.
  • Flat roofs have smaller lifespans than pitched or sloping roofs.

Types of Flat Roofing

Flat roofing is generally built up using one or more variants of membrane roofing technology.

Three major types of flat roofing are discussed below:

  • Built-up Roof Membrane Built-up roof membrane (BUR) is the commonest of flat roofing examples. It is pre-cast and assembled on site using additives. It contains three or more layers of base and insulation that are reinforced with bitumen and/or coal. Another layer of aggregate, such as sand and stone, is cast on top to prevent UV rays from damaging the inner layers.
  • Fluid Roof Membrane Fluid roof membrane is a type of flat roofing in which adhesive fluids are used to bind base, insulation and top layers together, without creating a rigid surface. Fluid roof membranes are most commonly use on domes and non-uniform roofs.
  • Polymer Enhanced Membrane Polymer enhanced membrane roofs employ polymers or elastomers like HDPE, PVC and EPDM to create a level-surface atop the base and insulation layers.

Installing Flat Roofing

A short and quick guide to installing a flat roofing is given below.

  1. Before installing a flat roofing, you need to make sure that you have gained all the relevant grants from local authorities.
  2. A flat roofing should be designed and approved by a qualified contractor and engineer first, before you actually move on to the installation.
  3. For installing a flat roof, construction of steel skeleton is first necessary. Once the steel frame is ready, you can rest the base layer ply and insulation layers on it. These layers can the either be mechanically affixed or glued in place.
  4. Once the base layers are in place, the membrane layers needs to be attached to them using suitable methods(s). Common methods include torching, adhering, bolting and gluing.
  5. The roof needs to be allowed to weather cure for at least 48 hours before it can be inspected and tested for strength.

Sustainability and Maintenance of a Flat Roof

Flat roofs are generally considered to be non-sustainable due to the fact that they have a shorter life span than most other types of roofing. The only factor that can possibly contribute to their eco-positivity is the reduction in the consumption of power they effect due to improved insulation.

For efficiently maintaining a flat roof, following guidelines can be followed:

    Torch-down roofing can be considered as a clever manipulation of two method – on site tar boiling and on site membrane application.

    In torch-down roofing, a sheet of modified asphalt/bitumen is rolled over base layers of gravel that are heated locally using a high-temperature propane blowtorch.

    A 100 sq. ft. area covering mat would weigh around 100 lbs. 

Torch-down Roofing

Torch-down Roofing being installed
Figure 14: Torch-down Roofing being installed (Image Credit: YouTube)

Torch-down roofing can be considered as a clever manipulation of two method – on site tar boiling and on site membrane application.

In torch-down roofing, a sheet of modified asphalt/bitumen is rolled over base layers of gravel that are heated locally using a high-temperature propane blowtorch.

A 100 sq. ft. area covering mat would weigh around 100 lbs. 

Pros of Torch-down Roofing

  • Torch-down roofing is relatively cheaper.
  • It provides excellent UV protection and insulation.
  • Torch-down roofing does not need much maintenance.
  • It has a long life of over 30 years.

Cons of Torch-down Roofing

  • Torch-down roofing carried fire hazards during installation.
  • It is not entirely eco-friendly.
  • Torch-down roofing has nothing much to add to the outlook of the building from the aesthetic viewpoint.

Installing Torch-down Roofing

Installation of a torch-down roofing is exactly the same as that of bitumen roofing that was discussed earlier.

The only difference lies in the fact that a torch-down roofing requires a longer curing period (72 hours, in the least) than bitumen roofing.

Sustainability and Maintenance of Torch-down Roofing

Torch-down roofs, because they are usually made of polymeric materials or asphalt, are not entirely sustainable. They cannot be easily recycled and hence, do not possess a high-degree of reusability.

From the maintenance point of view, a torch-down roof is really user friendly. As few as two inspections every year are good enough to ensure good functionality of a torch-down roof. Occasional wear and tear should be dealt with compatible PVC glues and/or bitumen/HDPE/PVC/EPDM patches.


Domestic Roof Construction

After discussing various types of roofs, a brief discussion about generic roof construction procedure is to follow here.

Without going into the technicalities of the whole procedure, domestic roof construction can be divided into three broad stages:

  1. Design

    Design of every roof involves a large number of considerations from the following points of view:

    • Structural
    • Financial
    • Mechanical
    • Aesthetic
    • Utility
    • Maintenance
    • Cost-effectivity
    • Durability

    Based on these considerations, a design that suits the building is prepared and is processed for planning permissions.

  2. Preparation

    Preparation state of domestic roof construction involves creating a framework for roofing material to rest on. This framework usually takes help of steel members, wooden planks, ply members, timber framework etc. – depending upon the availability of materials and purpose of the construction.

  3. Roofing

    The actual roofing process follows next. In this process, base layer is first affixed to the framework. Insulation layers, if any, follow next. The roofing material (modified bitumen, for example) is the applied over the insulation layers, and allowed to cure naturally for a designated period of time.


Owens Corning

Owens Corning is a well-known name in the global roofing industry. It is the first truly multinational roofing company that operates in over 100 different countries.

The company was founded in Toledo, Ohio in 1938, in the wake of a depression decade in the United States, and at the mouth of the World War II. The company was offered to the public in 1955, and holds the distinction of being a Fortune 500 Company for over six decades without failure.

The company is best known for:

  1. Their ground-breaking research in improving domestic roofing insulation that has led to enormous savings in power consumption at homes.
  2. Their range of excellent insulation technologies that are easy to adapt and adopt.
  3. Their customisable roofing solutions for domestic as well as commercial buildings.
  4. Their incessant efforts towards creating public awareness towards efficiency of roofing and related environmental implications. The company has been at the forefront of environmental sustenance and its extension to roofing technologies.

Owens Corning has corporate offices in over 30 countries and over 15,000 professionals are employed by the company. Total assets of the company are estimated to be worth over $7 billion, with average annual revenue for the last five years being upwards of $200 million.


Wood Shakes

Wood Shakes
Figure 15: Wood Shakes (Image Credit:

Wood shakes are often confused for wood shingles. There’s a subtle difference between the two. Wood shakes are often broader, thicker, coarser than wood shingles and are often hand-split or crafted.

Wood shakes render a certain rustic and natural feel to the roof, making them more expensive than wood shingles.


Wood Shingles

Cider Wood Shingles on a roof in Arkansas
Figure 16: Cider Wood Shingles on a roof in Arkansas (Image Credit:

Wood shingles are like all other shingles. They are uniform, can interlock and intersperse with each other and can create a knitted pattern that is water and weather proof.

Wood shingles are often opted for domestic roofing applications because they create a beautiful frontal look that few other roofing techniques can – without compromising with the quality of the roofing to any extent!


Roof Coating

A roof coating is a coating that is applied to the roof in order to add or enhance certain performance factors of the roof.

Most coatings – excepting certain elastomeric coats – are cold applied, meaning that they are applied at the room temperature, without any special pre-heating of the roof.

Some of the commonest of purposes and aims achieved by applying various roof coatings are:

  1. The commonest purpose that roof coatings are applied for is to proof the roof against UV rays of sunlight.
  2. Another common reason for applying roof coatings is to enhance the waterproofing degree of roofs – especially aged roofs.
  3. Roof coatings are also applied in order to improve insulation provided by the roof. White coats are applied in regions to reflect sunlight in order to keep indoor temperature lower.

There are certain facts about roof coatings that, however, need to be noted before actually opting them. Roof coatings do not make a roof stronger or more efficient. Roof coatings should always be looked at as performance enhancers – not performers in themselves.


Membrane Roofing

Membrane roofing is a type of roofing that has gained tremendous popularity in recent years because of its easy installation and durability.

What is Membrane Roofing?

Membrane roofing involves the use of a membrane of polymeric or elastomeric material (PVC, EPDM, HDPE etc.) in order to enhance the performance of a roof. The layer of membrane is often applied once the base layer and the insulation layer have settled. A membrane roof is often more efficient in water and weather proofing areas than a regular asphalt roof.

Types of Membrane Roofing

There are three major types of membrane roofing:

  • Modified Bitumen Roofing We have already discussed this type earlier in this article. Modified bitumen roofing is a great insulator and is used widely in colder climatic conditions.
  • Thermoset Membrane Roofing Thermoset membrane roofing involves the use of a thermal polymer lie EPDM that sets in to create a giant covalent polymeric structure after allowed to cure in natural sunlight for over 48 hours.
  • Thermoplastic Membrane Roofing Thermoplastic membranes work quite similar to thermoset membranes. However, instead of chemical polymerization, they are linked and strengthened via external heat, often using a propane blowtorch.

Installing Membrane Roofing

Installation guidelines for bitumen and rubber roofing have already been discussed in brief in sections that preceded this one, during the course of this article. Those guidelines can be referred to as generic guidelines for installation of all membrane roofing types.

There can be certain varieties – especially in cases where thermoplastic membranes are being used. Excess care needs to be taken to maintain the safety of the personnel performing the installation, as well as the building itself.


CertainTeed Corp. is a widely known building material manufacturer and distributor operating chiefly across North America.

Table 3: CertainTeed Corporation – A Fact File

Name of the Company

CertainTeed Corp.

Wholly Owned By

Compagnie de Saint-Gobain SA

Founded In



Over $5.5 billion[6]

Operations Spread Over

50 countries

Number of Employees

Over 6,500


  1. Roof coatings
  2. Roof insulation products
  3. Vinyl roofing solutions
  4. Roofing tiles (cement, plastic, vinyl, composites)
  5. Over 100 trademarked shingle variants (metal, rubber, composites, EPDM, asphalt, bitumen etc.)

[6] Source – Forbes USA, 2014


Slater’ is a term that has been traditionally used in the United States to refer to a professional who specializes in setting up and installing slates to form a slate roof.

Today, slating has become a more and more mechanized process that has made the very profession of slaters a bit redundant. However, there is still high demand for expert slaters who can seamlessly join slates to create a perfect slate roof.