Asphalt Shingling, Built-Up Roofing and Wood Shingling
Asphalt shingles are the most common type of roofing material used on pitched roofs. They are lightweight, comparatively inexpensive, and available in many different colors, sizes, and shapes.
Asphalt shingles are sold in the form of individual shingles or as strips of shingles joined together in two, three, or four tab units. The strips are 36-inches long. Their width will vary from slightly over 11 inches to 12 inches wide, depending upon the style and manufacturer. Lock-type asphalt shingles are also available in a number of different styles.
Before laying a new roof with asphalt shingles, you must first calculate the total area to be covered. A high school plane geometry text will provide you with the formulas necessary to calculate the square footage of surface area. Many roofs form uncomplicated rectangular or squares.
Unfortunately, hip roofs, dormer roofs, and other types of minor roofs present more complicated surfaces. In any event, the total square foot area of the roof covering the structure must be calculated.
When you are satisfied with your calculations, go to your local building supply dealer and purchase the shingles. Large quantities of shingles are sold in units (squares) that will cover 100 square feet of roof area. Each square will contain 3 bundles of asphalt shingles. You will also need nails. The type and number of nails is generally recommended by the shingle manufacturer. The manufacturer will also recommend the amount of exposure (usually about 5 inches) for the shingles and instructions for nailing.
Additional supplies for asphalt shingling include enough roofing felt or paper to cover the roof and serve as a base for the shingles; a suitable flashing material; and enough roofing cement to do the job.
Before asphalt shingles are applied, the entire roof must be covered with asphalt impregnated roofing felt. The roofing felt is stapled or nailed to the sheathing with each course overlapping the preceding one by approximately 2-3 inches.
When used, flashing along eaves and gable ends should be applied after the roofing felt has been laid. The flashing around chimneys, vents, and dormers, and along the roof ridge can either be applied before the shingles are laid, or when the asphalt shingles reach those points on the roof.
Many professional roofers begin by laying a starter strip of asphalt shingles along the roof eave. The shingles in the starter strip are laid face down with their top edge flush with the eave or flashing. The first course of asphalt shingles is laid directly over the starter strip and nailed to the sheathing.
A chalk line is used to establish the position of successive courses of asphalt shingles. Each course is laid so that there is approximately 5 inches of exposure and the tabs are staggered. The shingle manufacturer will generally recommend the type of nail and nailing pattern to use.
Each course of shingles should be laid so that the breaks between individual shingles (or tabs) are staggered. This can be done by beginning at the center of the roof and working toward the gables (or hips) and then cutting off the excess shingle to conform to the edge of the roof when it meets the gable. Another method is to begin at one end of the roof and work toward the other. Both methods involve trimming the shingles to conform to the roof edge.
On some roofs, the valleys are left exposed. The shingles are cut at an angle parallel to the roof joint, but overlapping the flashing by 2 or 3 inches. A chalk line should be struck the length of the flashing 2 or 3 inches in from each edge. The shingles that form the border with the flashing should be coated with asphalt roofing cement and nailed to the roof. When the flashing is left exposed, it should be the same color as the shingles.
Some workers prefer to cover the roof valleys with shingles rather than to leave them open. There are two ways to do this. One method is to cut the shingles on both the main and minor roofs so that they form a close fit. The valley is lined with a double course of roofing felt first, and the shingles in the valley are fastened to the roof with nails and asphalt roofing cement.
The second method of covering a roof valley consists of shingling over it in overlapping courses. This is possible with asphalt shingles, because they are flexible and can be bent to conform to the angle of the valley. Care must be taken, however to bend them carefully and not break them.
Because these overlapping courses of shingles do not lie flat against the surface of the valley, you should apply valley flashing beneath them to protect the roof joint from leaks (see Valley Flashing).
SHINGLING HIP ROOFS
A hip roof is one which slopes upward from each wall toward the ridge. The degree of slope will depend on the pitch of the hip rafters, which extend from the outside corners of the structure to the ridge or a common rafter.
The recommended method of shingling a hip roof is to lay each course of shingles completely around the entire roof. Cut and fit the shingles of each course around each hip ridge. When all the courses have been laid, cover each hip ridge with a course of shingles.
Begin at the eave and lay the course of hip ridge shingles in the direction of the main roof ridge. The hip ridge shingles must be applied before the shingles on the main roof ridge. Four nails are used with each hip ridge shingle. Two of the nails should be very close to the hip ridge. The other two are approximately 1 inch from the outside edge of the shingle.
Ridge shingles are used to cover the ridge line of the main roof. The ridge shingles on a main roof are started at both ends. The work moves toward the center of the roof where both courses meet. Four nails are used to attach each ridge shingle. Ridge shingles can be made by cutting ordinary shingles to the size required, or specially made shingles for this purpose can be purchased.
REPAIRING AN ASPHALT SHINGLE ROOF
One problem encountered when repairing an asphalt shingle roof is getting new shingles that will match the old ones. There are quite a few different manufacturers, and it is not uncommon for them to discontinue a color or style.
If the asphalt shingles on your roof represent a discontinued line, you will have to find replacements that match the old ones in color and style as closely as possible; otherwise, the new shingles will provide a sharp contrast with the older ones. Take a piece of the damaged shingles into your local building supply house and try to match it in weight, color, and style. Try to get the overall dimensions of the shingle (e.g. 36 inches x 12 inches, 12 inches x 12 inches, etc.) so that you can also match sizes.
Strong winds will sometimes cause a shingle or shingle tab to bend and peel up from the roof. If the shingle has not been broken, it can be repaired by spreading asphalt roofing cement on the bottom of the shingle and pressing it down. If the shingle won’t lie flat, nail it at the edge and cover the nail head with a dab of roofing cement.
Small tears can be mended in the same way if they do not extend up under the overlapping shingles of the next higher course. Coat the bottom of the torn shingle with roofing cement, firmly press the two sections together and down with roofing cement.
Seriously damaged shingles must be removed and replaced. Insert a hacksaw blade under the shingle and cut the nails holding it to the roof. Pull out the shingle and repair any holes or rips in the roofing felt with a patch and some roofing cement. Install a new shingle and nail it in place. Use roofing cement on the bottom of the shingle.
A good roof should last quite a number of years, but eventually you will be faced with the problem of laying a new roof. This can be done by completely removing the old one and laying a new one, or reroofing over the old material. Reroofing is possible if the old roof consists of a single layer of asphalt shingles, roll roofing, or wood shingles.
You should never reroof if the sheathing shows signs of damage or rot. You can check for this by examining the bottom of the sheathing in the attic or attic crawl space. If these conditions exist, remove the old roofing materials, repair the sheathing, and lay a new roof.
When reroofing with asphalt shingles over an existing roof of the same material, begin with a starter course of shingles along the roof eave. Lay a second course of shingles over the first one to form a double row, staggering the breaks in the shingles. Lay each course toward the ridge with about a 5 inch exposure for the shingles. The nailing method is identical to the one described in the section covering asphalt shingling.
There are also a number of special roofing compounds available in different colors that can be used to cover an old shingle roof. Your local dealer will have information about them and instructions on how to apply them.
Labor costs and the time required to do the job are significantly reduced if the old shingles (or other roof covering materials) do not have to be removed. Furthermore, the additional thickness of roofing material reduces the amount of heat loss in the winter. Finally, if the work should be interrupted by rain, the interior of the structure is protected by the old roof. Asphalt shingles can also be applied over wood shingles.
In order to do this, the wood shingles should be in reasonably good condition and dry. Replace rusty or loose nails with new ones, and cover the heads with roofing cement. Before reroofing, nail down loose shingles and repair any leaks you find.
Some roofers prefer to remove the old wood shingles along the eave and gable, and replace them with 1 X 4 (or 1 x 6) boards nailed to the rafters. The roof is then covered with ply’s-cord sheathing which is nailed to these boards and to the rafters under the wood shingles with nails of sufficient length. Roofing felt, flashing and a starter strip of asphalt shingles is then applied as previously described.
GUTTERS AND DOWNSPOUTS
Gutters and downspouts (leaders) are generally made from metal or plastic, although wood gutters are sometimes encountered on older houses and buildings.
There are two methods of attaching gutters. One method is to nail or screw the gutters to the roof sheathing by means of a flange or strap after which the shingles or other roof covering materials are applied. Another method is to nail or screw the gutter to the fascia of the structure after roofing has been completed.
Aluminum gutters and downspouts are recommended for replacing existing ones, because they are light, strong and seldom subject to corrosion. When they do corrode, it is generally in a locale near salt water. Gutters can become clogged with leaves or other debris.
This can result in water overflowing from the gutters and running down the walls, resulting in possible interior wall damage. The gutters can be kept free of debris by covering them with screens. The screens must be cut wide enough to extend up under the shingles or other roof covering materials, and to bend over the outside edge of the gutter. Make sure the gutter screen also covers the opening to the downspout.
Clogged downspouts can be flushed out with a garden hose or cleaned out with a plumber’s auger. If neither of these methods works, the downspout should be replaced with a new one, preferably one made of aluminum.
If water collects in the gutter and does not drain toward the downspout, then the gutter does not have enough slopes to it. Detach the gutter and reattach it so that there is at least a slight downward pitch toward the downspout. Before reattaching the gutter, fill in the old nail or screw holes with roofing cement. The heads of all nails or screws used to attach gutters should be covered with roofing cement. If the gutter strap or flange is fastened to the roof sheathing rather than the fascia, it should be fastened under the roofing felt.
Small holes in gutters can be repaired with a sealer, but it must be one that will bond with the gutter material. For example, aluminum caulking is recommended for aluminum gutters. Galvanized gutters on the other hand, should be soldered. A suitable epoxy cement or glue can be used successfully on a number of different materials. Your local building supply dealer can recommend a suitable sealer.
Roll roofing is an asphalt coated material used both as a roof covering and as an underlying base for tile, slate, and other roofing materials. Both smooth surfaced and mineral surfaced roll roofing are available. The latter is recommended if the roll roofing is to be used as roof covering, because the mineral granules protect the asphalt coating of the material from weather Conditions.
Smooth surfaced roll roofing is often used on farm out buildings, sheds, or temporary structures. It is inexpensive, easy to install, but rather unattractive. Mineral-surfaced roll roofing is preferred when appearance is an important factor, and is available in a number of different colors or color combinations.
Follow the manufacturer’s instructions when applying roll roofing. It is generally available in 36-inch wide strips, and should be applied with each course overlapping the preceding one by approximately half the width of the roll.
Roll roofing is also available with the lower half coated with mineral granules and the upper half smooth. With this type of roll roofing, the smooth portion is overlapped by the next highest course.
The manufacturer of the roll roofing will generally provide instruction on how to apply it, and will recommend the type and spacing of nails to use. Some roofers use a starter strip laid along the roof eave.
The starter strip should be at least one half the width of a regular roll roofing course (i.e. 18 inches). If it is mineral surfaced roll roofing, then the mineral surfaced slide should be laid against the sheathing.
Whenever applying roll roofing, cover the area over which the material is to be laid with asphalt roofing cement. As you lay each course, roll it smooth with a roofer’s roller to eliminate air pockets and wrinkles, and to insure a tight bond.
After each course has been rolled, nail it to the sheathing every foot or so. The nails are placed in the upper half of each course (i.e. the portion to be overlapped by the next highest course).
ROLL ROOFING REPAIRS
Small holes, rips, or loose seams that are not too extensive can be repaired by applying roofing cement and pressing the roll roofing back in place. Procedure can be out lined as follows:
1. Cover the damaged area with a piece of roll roofing cut several inches larger.
2. Coat the bottom of the roll roofing patch with roofing cement.
3. Nail the patch in place with roofing nails (large head types).
4. Apply roofing cement to the top and edges of the patch to seal it.
Built-up roofing is installed on flat roofs or roofs with a very low pitch. This type of roof covering consists of several layers of lapped roofing felt and alternating layers of asphalt roofing cement, or hot roofing pitch. Applying built-up roofing is difficult and requires special equipment. Only those with experience should try to apply built-up roofing.
The first layer of roofing felt is laid along the roof eave or edge and nailed to the sheathing. The nails should be positioned approximately 5 inches apart and about 1 inch from the edge of the strip. Each strip of roofing felt is 36 inches wide. Measure in one third the width and strike a line parallel to the edge of the strip. Nail along these two lines so that the nail heads are one foot apart and staggered.
Cover the first layer of roofing felt with asphalt roofing cement, and immediately cover it with a second course of roofing felt. The second course should overlap the first one by at least 6 inches, but not more than 10 inches. Nail the bottom edge and then roll the second course so that it is securely bonded with the first course and all air pockets and wrinkles have been eliminated. Finish nailing the second course in the same way that you nail the first one.
Continue laying courses of roofing felt until the entire roof is covered. Use the same procedure described for the first and second courses.
When you have completely covered the roof with roofing felt, cover the entire surface with a layer of asphalt roofing cement. Greater resistance to weather conditions can be obtained by sprinkling gravel or some other suitable mineral before the final coat of roofing cement dries. If you finish with gravel, a retainer strip should be nailed along the roof edge.
REPAIRING BUILT-UP ROOFING
Leaks in built-up roofing usually result from blisters or cracks that develop on the surface. Both blisters and cracks should be cleaned first before attempting to repair them.
Brush any gravel, dirt or dust out of the damaged area. If the damaged area is small enough, it can be covered with roofing cement. Larger areas should be repaired with a patch cut from roofing felt.
Wood shingles are generally available in lengths cut to 16, 18, and 24 inches. The widths will vary on a random basis. Shakes are similar to wood shingles in appearance, but are cut thicker and larger. Wood shingles are most commonly used on roofs with a ‘A pitch (i.e. 4 inches rise for each 12 inches or run) or more. On roofs with less than ‘A pitch, a professional roofer should do the work because special application procedures are involved.
Many workers lay wood shingles directly over the roof sheathing on new roofs. Wood shingles tend to retain moisture. If there is no roofing felt between the sheathing and the shingles, the extra ventilation will enable them to dry out faster. Even better ventilation is provided by laying the shingles on wood slats (shingle lathe). The slats consist of nominal 1 X 3 or 1 X 4 boards nailed to the roof rafters and spaced an equal distance apart. Three slats joined together, or a board of approximately equal size, is nailed along the roof eave when wood shingles are used.
Wood shingles are nailed to the sheathing or shingle lathe with zinc coated, corrosion resistant nails. At least two nails should be used to fasten each shingle. They should be placed at least 1 inch from any shingle edge, and at least 1inch under the overlay of the next course. Because wood shingles absorb moisture, they should be spaced approximately VA inch apart to allow for expansion. If you do not allow for the expansion, the shingles will buckle and split.
Each shingle should be attached to the roof with two nails spaced 1 inch from the edge of the shingle and 1 inch above the bottom edge of the next course.
The procedure for applying wood shingles to a new roof may be summarized as follows:
1. Cover the sheathing or shingle lathe with asphalt roofing felt and lay the flashing in the valleys.
2. Nail a starter course of shingles spaced 1/4 inch apart along the roof eave. Allow the starter course to over-hang the roof edge 1Vz inches.
3. Cut a shingle to fit the angle of each valley and nail it to the roof.
4. Lay the first course of wood shingles over the starter course so that the vertical joints do not align with those below.
5. Stagger the vertical joints in each course as you lay the shingles up the slope of the roof.
REPAIRING WOOD SHINGLES
The expansion and contraction of wood shingles sometimes causes them to crack and split. This tends to be one of the principal problems with wood shingle roofs, but it is not a difficult one to correct. Cut a piece of copper, aluminum, tin or roofing felt to size and insert it under the damaged shingle. Nail both halves of the shingle to the roof, and cover each nail head with a dab of roofing cement. Galvanized roofing nails are recommended for nailing the shingle, because they resist corrosion well. Warped shingles should be split lengthwise with a chisel, and repaired in the same way.
Badly damaged or rotten wood shingles should be replaced. Remove the unwanted shingle by slipping a hacksaw blade under it and cutting the nails. The new shingle should match the color of the old one as closely as possible. Never paint wood shingles. Shingles can be stained if you want to change or add color, but this should be done before they are laid.