If your home has the original (or only one) shingle roof on it, the building code allows you to overlay it once with a new roof. If your roof has already been overlaid once, you must tear off both the overlay and the original roof down to the plywood or plank sheathing.
Weight is a key reason for the maximum limit of two roof systems on a home.
22 squares = 66 bundles: 66 bundles x 75 lbs./ bundle = 4,960 lbs.: 4,960 lbs./2,000 lbs./ton = 2.48 tons
Overlaying this roof will double the amount of the permanent weight, or “dead load,” to a total of five tons. This is within the code. If someone disregards the code and puts on three roofs, they now have seven and a half tons overhead. Ice or snow will add tons of weight (“dead load”). Wind causes loading, but the wind is shifting and variable so it is considered a “live load.” Seven and a half tons of roofing material and a few tons of snow and ice combined with the “live load” from a blast of high wind can cause a roof to fail without warning.
The other key reason for only two roofs is that you want your roofing nails to penetrate the sheathing to give you maximum hold. If you try to put on a third roof, the shaft of your roofing nail has to go through three overlapping layers of shingles and may just barely penetrate the wood sheathing. When you nail new shingles to nothing but old shingles, a high wind will peel your new roof like a banana.
Having said all that overlaying, the original or a single roof is by far the preferable situation in terms of labor mess and risks due to weather.
An unscrupulous contractor may try to talk you into an overlay even if you already have two roofs on your home. If you are dealing with someone who isn’t licensed and isn’t insured anyway, what does he care?
A favorite ploy of unscrupulous contractors is to “cut the tabs” on a shingle roof that is badly curled. This is cutting and removing the exposed portion of each course of shingles. They simply go along with a knife and use the bottom of the exposed tabs of each row of shingles to cut off the exposed tabs of the course down the roof. They cut their way up the roof, and all they have to do is throw away a bunch of 5″ x 12″ shingle tabs with no nails in them.
They don’t have to replace the felt, pop new chalk lines, treat the valleys, etc., so they can naturally discount the price to the consumer ever so slightly.
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Some homeowners spring for this kind of deal, but remember, if the tabs are cut on an existing second roof, less than XU of the overhead weight is removed, and there is still the problem of full nail penetration through the sheathing.
DON’T PUT IT OFF
Procrastination does not pay when you are deciding to overlay your original roof. If your original roof was laid using twenty-year shingles, start keeping a close eye on it at the fifteen-year mark. While it is true the roof can last twenty years, the shingles at twenty years may be so brittle, curled, and broken up that you can’t overlay it.
A brittle roof will crunch like com flakes when you walk on it. Don’t try to overlay a roof that is brittle. Small chunks of shingle and grit will roll down the roof as you work on it, and they will get between and under your new shingles unless you constantly brush away the pieces that roll down the roof. It will take less time and be less aggravating to go ahead and tear off an old roof like this.
If you look up the pitch of your roof from the ground, and your shingles look swollen in sections or have a “bear claw curl,” the unevenness will not only show through your new shingles, but you will still contend with the broken pieces rolling under your new shingles. My advice again is to tear it off.
Contractors who don’t own a dump truck are especially prone to push for an overlay, no matter what the condition of your original roof.
When a roof is torn off and the shingles and asphalt felt underlayment, or “paper,” are thrown in the back of a pickup and sit in the sun for several days, everything tends to weld together into a single nail- and metal-laden mass. Think about trying to get that stuff off by hand. When we emptied our big dump truck, we usually had the tear-off from three houses in it. Despite being dumped and occasionally dragged, the material stayed in the perfect shape of the dump bed. If you are doing a tear-off, don’t let the trash sit long enough to bond.
BASIC INFORMATION ABOUT SHINGLES
The standard modem shingle is a rolled laminate of fiberglass matting and asphalt with a surface of various colored grit. The top of the shingle is solid across its entire 36-inch width. The grit on the top is basically black. The bottom of the shingle will be the exposed portion, and the grit on the bottom gives the shingle its color. The bottom of the shingle is notched out at 12 inches and 24 inches with keys that are 3/s inch across and 5lk inches long. Each end of the shingle is trimmed to form a half-key. The keys form three “tabs” in the bottom of the shingle. You will make your measurements and lay your courses based on the top, full 36-inch width, of the shingles.
The tabs allow the shingles to be flexible, so they will lie flat over imperfections in the original shingle roof or sheathing underneath. The tabs also limit the amount of damage from severe winds. The shingle is cut into tabs so that a high wind can tear the tab off. It is better to lose a fairly small 12-inch tab than a full 36-inch shingle.
The manufacturer cuts the shingles within certain fairly small tolerances (usually +/-V16 inch). How-ever, trouble with odd-sized shingles does occasionally happen. The first time I saw this, the key-way s (vertical alignment of the keys up the roof) on the house I was roofing were waving all over the place. The last thing I checked was the width of the shingles themselves. I found some to be not 36 inches but 36V2 inches across the top.
A poor contractor is not going to worry about whether your keyways are straight A shoddy contractor’s keyways aren’t very straight even if his shingles are cut perfectly at the factory. He will try to convince you that straight keyways aren’t important
Nails should be driven above the keys and just below the asphalt self-sealing strip. Nailing in this spot ensures that the tab for the next course up the roof will center over the nail head and cover it fully.
Also the pressure from the nail tends to raise the self-sealing strip, which makes it seal more fully to the shingle above.
If you are nailing into plank sheathing, you may find that you nailed directly over a gap between the planks. If you already drove a nail that didn’t “bite,” leave that nail in place so there won’t be a hole. Nail the shingle again, keeping your nails up higher above the gap in the planks. Now nail your new course higher. If necessary, stay above the self-sealing strip with your nails. Don’t go any higher above your optimum nailing position than you have to, but make sure you nail into solid wood.
Your nail head should be driven down snug with the surface of the shingles. Don’t drive the head into or through the shingle. (If you use a nail gun, be especially careful to set your air pressure low enough so the nail heads don’t tear into the shingle.) When the head goes through, the asphalt has been cracked and the fiberglass torn. It’s a weak spot. It may never leak, but why take the chance? If you are using a gun, carry a claw hammer with you to drive down the occasional nail the gun doesn’t drive flush.
Now get roofing! The first thing you need to do is cut off your shingles where they protrude over the edge of your roof or rake. The trim board that runs up the side of your roof from the gutter to the caps is called your rake board. Cutting off the protective overhang of your old roof is called cutting the rakes.
On most homes, the carpentry on the rakes is straight, but as a precaution, sight up your rakes from the ground. Are the rake boards straight? Are they bowed in or bowed out? If they are bowed in toward the house, it’s not a problem as far as reroofing is concerned. If the rake is bowed in more than half an inch, you need to decide if you are going to cut the rake off the old roof, following the bow in the rake board, or if you will follow a straight line up the roof to support your new shingles over the bowed area.
Go to the rake, just above the fascia. Using your hook blade, trim the shingles back gradually to the face of the rake board. Now make a short slice up the roof and all the way through the shingles, making sure it is even with the face of the rake. Go to the peak of the roof just below the cap pieces and again gradually notch back to the face of the rake. Go back down the roof and hook the metal nail hook from your chalk line securely in the short slice you made. (If you don’t have a metal nail hook, tie the end of your line to a standard metal washer.) Now reel your chalk line out. (You may need to bang the side of the box on your hand to loosen the chalk powder as the line comes out.) Pull the chalk line taut and hold it directly above the face of the rake board so that you can see through your notch at the caps. Holding the line firmly with one hand, raise the line straight up and “pop it” (release it). You have just “popped a line” above the face of your rake board.
Now you need to cut the rake. It is easiest to start at the top and cut down the rake. Tuck one leg and use your other leg as a brake and brace. Use the hand closest to the roof to hold the top outside edge of the shingle to be cut. With your other hand, slowly pull the hook blade down the blue chalk line on the top shingle. Cut the upper portion of the next shingle down the roof using the edge of the shingle you just cut as a guide for your blade. Finish cutting this shingle, using the chalk line to guide your blade.
Don’t cut toward your hand or your body — ever! Lay the pieces you trim on the roof above you and collect them when you finish cutting the rake. It’s easier to pick the pieces up off the roof than to fish them out of a flower border or shrubs. When you get close to the bottom of the rake, turn around and pull your hook blade up the roof.
If you have tough knees, you can just squat with your back up the roof to make this cut. If you are like me and want to be able to walk the next day, tuck one leg under and plant your other foot firmly on the roof, using your leg as a brace and the sole of your shoe as a brake. If you are right-handed, tuck your right leg and get it out of your way. Be careful not to pull against the knife so hard that you pull your-self off balance.
Too many contractors “cut the rake” on the old roof with the hatchet end of a roofing hammer. They hack the overhang off along a jagged line an inch or so behind the face of the rake board. New shingles won’t stay straight over this hacked area plus the required 1-inch overhang beyond the rake.
The edges of the new roof soon curl in a pronounced downward hump, which begins before the shingles even reach the rake board.
Your new shingles will be strong and come straight off the lower edge of your roof (fascia) above your gutter. Your old shingles may have drooped down and become ragged where they overhang the trim board covering the end of your joists (fascia board). To make your new roof look neat, you need to cut along the fascia. Repeat the same notching process at both ends of your fascia and pop a line across the lower edge of your roof. If your roof is extremely long, you may have to cut another notch in the middle and pop the line in two steps.
Now you need to “cut the third course.” Let me give you some background on this. Your roof is already two shingles thick at its lower edge. Your new roof will also be two shingles thick at its lower edge. This means your new roof will be four shingles thick at the fascia. This extra thickness will create an unsightly hump where the extra thickness changes down to a normal thickness. To eliminate this hump, you need to taper the thickness of shingles gradually from four back to two. You do this by cutting the third course.
Your shingles are 12 inches high, and you will let them overhang your gutter 1V2 inches. The top edge of your new shingles will be IOV2 inches above the fascia cut you just completed. (12.0 – 1.5 = 10.5 inches)
Some roofers cut off the third course and use the cut edge as a guide for laying the new shingles. You should give yourself a little room and measure 11inches up from the face of the fascia board and notch the shingles at the rake. Hook a chalk line in the notch and measure up 11 inches on the other end of the roof. Pop a line at 11 inches. Now cut the tabs of the third course at the chalk line and remove the cut tab sections from the roof.
A bad contractor won’t do any of the preparation and cutting covered so far. He will leave the ragged rake and fascia edges of the old roof showing under your new one. By not cutting off your third course, he will leave a pronounced and unsightly hump in your shingles. Some contractors who do cut off the third course, do exactly that.
They cut off the third course even with the bottom of the shingles of the fourth course. This removes the entire 5 inches of the tabs of the third course instead of just the few inches at the bottom of the tabs that do need to come off. Removing the entire course causes a 2V2- to 3-inch gap underneath your new shingles. Your new shingles will try to bridge this gap, but will eventually dip down into it. Worse yet, your contractor will nail your new shingles down into this gap.
BOTTOM COURSE LINE
Allowing an overhang greater than IV2 inches will cause a standard strength twenty-year shingle to droop over the fascia. Measure up your roof IOV2 inches from your fascia. Use your straight blade to make a horizontal arrowhead mark at IOV2 inches.
Pull IOV2 inches at the other end of the fascia and drive a nail partway down at this measurement. Attach the nail hook on your chalk line and pop the 1072-inch line across the roof.
BASE LINE AND OFFSET LINE
I don’t recommend that you lay out your roof this way, but this is the way most roofers lay out the verticals, or vertical key ways up the roof. Your shingle is 36 inches wide, so if you measured in 36 inches from the face of your rake board and popped a line parallel to the face of your rake, the outside edge of your shingles will be exactly even with the face of your rake. But you have to have an overhang to protect the rake. A 1-inch overhang is generally accepted, but you will need to have enough shingle hanging out there that you can cut it easily with a hook blade. Allow yourself an extra inch to cut.
Subtract the amount of the overhang from the 36 inches to get the measurement from the rake to the base line.
36″ – 2″ = 34″
At the top of the roof, just below the caps measure in exactly 34 inches from the face of your rake. Mark the 34-inch measurement, using your straight blade to cut the point of an arrow in your old shingles. While your tape is still in place, mark a point 6 inches back toward the rake from your 34-inch base line measurement. This is the measurement for the offset line.
34″ – 6″ = 28″
Drive a nail solidly into the exact point of each arrow mark at the top of the roof, leaving part of the shaft of the nail exposed. Tie or hook a chalk line to the nail at the 34-inch mark. Mark the 34-inch measurement at the bottom of the roof. Hold the line tight over the 34-inch mark at the bottom of the roof and pop a line. Repeat the process for the 28-inch marks. You now have your base line and offset line to lay your shingles.
So far, this seems simple enough. Now I’m going to make things tougher for you. I don’t want you doing it this way! The problem with just popping a base line and an offset line along the rake of the roof is that your error accumulates as you lay shingles across the roof. Your key ways as you progress toward your far rake become increasingly wavy.
You may butt the ends of the shingles tighter one time and slightly looser the next. This causes a slight distortion of your key way. Compounding the problem is the fact that shingles are not cut to microscopic perfection. They are the same size within certain tolerances (+/-V16 inch). The acceptable variation in widths of the individual shingles will also cause your key ways to wave as you sight up your finished roof. If you pull the measurements for the base line and offset line close to the middle of the roof section, you cut your natural error at each end by half of what it would have been on the far end, if you set the base and offset at 34 inches and 28 inches and simply ran your courses the entire Ip.npfh of the roof.
Bear with me, because it’s not complicated to get your lines in the center of the roof. Say you have a roof that is 35’8″ from rake to rake. You want a 2-inch overhang at each rake so:
35’8″ + 2″ + 2″ = 36′
Each shingle is 3 feet wide at the top. 36′ length of roof/3′ per shingle =12 shingles So about 12/2 = 6 shingles will put you at the center. 6 shingles x 3’/shingle =18′ Remember the 2-inch overhang over your rake so:
18′-2″ = 17’10″
Go just below the cap pieces and measure in from the face of your rake 17’ 10″ Mark it with your arrow using a straight blade knife. Now drop back 6 more inches to 17’10″ – 6″ = 17’4″ and mark another arrow for the offset line. Do the same thing just above the fascia. Drive nails and pop the base and offset lines. By taking this little bit of extra trouble, you keep the error from compounding all the way across the roof and the keyways will stay straighter.
Most subdivision houses were designed with multiples of the 3-foot width of shingles firmly in mind.
If you are in an older subdivision, older standard widths were in effect. If you are in a “one of a kind” home, your lengths of roof may bear no relation to a multiple of 3 feet. There will be examples of figuring odd sizes for you later.
Don’t get overeager and start yet. After you have a little experience cutting shingles, you may need less than a full inch to cut off at the rakes. Maybe you can change the amounts you subtract to IV2 inches and ll12 inches on the opposing roof. The less you have to cut off, the stronger your tabs along the rakes will be.
Your “starter course” is the first course of shingles, which forms the unbroken lower edge of your roof along the fascia. The starter course shingles are actually turned 180 degrees, with the grit still facing up, the tabs lying up the roof, and the top of the shingle overhanging the fascia into the gutter. Line the side of a shingle exactly on the center of your base line, with the shingle itself lying in the direction of the rake from which you measured. Line the bottoms of the tabs on the center of the bottom course line (IOV2 inches above the fascia). Nail the first shingle in place. Continue toward the rake you measured from by laying your next starter course shingle beside the first.
Lay the first shingle for your “first course” over the starter shingles you just laid. The first course is laid in the normal manner with the keys pointing toward the fascia. Center the end of this starter course shingle directly in line with the offset line, which is visible up the roof from the starter shingles. The starter course provides an unbroken surface beneath the keys of the first course and also doubles the strength of the new shingles at the fascia.
This is a fine point, but you may want to consider it. It’s a good idea to drop your first course down about Vs inch over the lower edge of the starter course. When your roof is completed, the water running off the shingles will tend to dribble back under the lower edge of your shingles. If the first course protrudes an additional Vs inch, the drips that try to dribble back will hit the edge of the underlying starter course and drop off rather than run back toward the fascia board.
The starter and first courses can be confusing when you first start roofing. Lay the starter course to both rakes, then come back and lay the first course.
Your final starter course shingle will overhang the rake you measure from by 2 inches. Your final first course shingle overhangs the rake with a long tab extending 8 inches beyond the rake.
LAYING THE ROOF
Some “roofers” make the mistake of jamming the shingles tight against each other, thinking it will make a “tighter” roof. Remember that shingles expand and contract and need a little breathing room just as people do. If shingles are jammed too tight against each other, they will tend to pucker or buckle.
One trick to keeping shingles from drooping over your rakes is to rough-cut the longer over hanging tab as you work up the roof. If you’ve got 8 inches sticking out over the rake, cut off 5 inches. That will keep the weight of the 8 inches from bending the tab down and possibly cracking the shingle at the rake.
Once a shingle cracks at the face of the rake, it’s going to drop from then on.
Too many contractors don’t trim the rakes until the end of the job. You can see the overhanging shingles flapping in the wind, and they end up broken and hanging straight down. The contractor can come back and cut these rakes fairly straight, bending them back up with his hand, and they will look pretty good for a short time (at least until he can cash your check). Then the shingles are going to droop over the rake. The only way to correct the situation is to replace all of the shingles along the rakes. If you are lucky enough to get this kind of contractor back, he will try to convince you that the shingles drooping over your rake give your rake board added protection. You might as well believe him; he’s not going to redo it
One of the great advantages of an overlay is that you don’t have to mark horizontal courses. Instead, you slide the top of the new shingle against the bottom of the tabs of the next course up the old roof. In effect, you are using the previous contractor’s courses (hoping they are straight). Butting the top of your shingles up against the bottom edges of the course above is called “nesting” the shingles (as in bird’s nest).
Now lay the second course up the roof. Line up the edge of the shingle with the base line and “nest” the top of the shingle against the bottom edge of the tabs of the fourth course of the old roof. Nail the shingle in place, being careful to keep your nails above the V2-inch gap between the top of your starter and first courses and the cut edge of the old third course.
When you come to the rakes, double nail the ends of the shingles. Nail once just below the self-sealing strip and nail again above that same nail, near the top of the shingle. Double nailing the rakes gives the roof tremendous extra strength in a high wind. Be careful that these end nails don’t split through the face of the rake board. Also, make sure they won’t show in the key way of the shingle in the next course up the roof.
Lay the third course shingle by centering the end of it over the offset line and nesting the top of it against the lower edge of the fifth course of the old roof.
Lay the fourth course by lining up on the base line again and nailing across. One costly and time-consuming mistake is failing to alternate courses between base and offset lines.
For example, if two consecutive courses are laid up the roof, both starting at the base line, the roof is open at the sides of the shingles and lets water through to the old original roof underneath. That original roof is now peppered with nails from the new overlay and is not waterproof. Keep checking yourself as you work your way up the roof. You don’t want to finish the section of roof and find that you failed to alternate courses down on the seventh or eighth course.
If you made this mistake, there is a way to fix it, especially if it’s a roof that can’t been seen. Carefully pull the nails on the upper of the two courses you failed to alternate. Slide a course of shingles between the two courses you messed up. If your two messed up courses both started at the base line, slide the correcting course in and start it 6 inches over at the offset line. Chalk line across your roof 2lh inches up from the lower edge of the bottom course where you made the error. Nail your correcting course in place with its lower edge on the 2V2-inch chalk line. Then nail your upper course back down.
If you discover this error on a roof that shows and you don’t want to roof the “mistake” again, get an answer ready. It will be a rare person who will be critical of the two courses (lower and correcting) that only have 2V2-inch tabs showings. But if some- one remarks on it, try responding with, “The roof looked so rigid and uniform. I wanted to customize it. Like it?”
I saw where one roofer discovered his mistake partway up the main roof of a home and then intentionally carried the same “short course theme” to the roof on a connecting wing. He then came down the same number of courses from the top and ran another short course on the main roof and wing. The owner was delighted with this very “distinctive” roof. Sometimes it’s not what it is, but what you call it. If you’re convincing enough, it may never be called a mistake.
The starter course and working position cause, the first four courses to go slowly. Once the fourth course is laid, you can turn around and face up the roof. (If you aren’t comfortable that close to the edge, go ahead and lay the fifth and sixth courses before you turn around. You aren’t trying to prove anything to anybody.)
Most modern shingles are designed to give a completely random pattern. The manufacturers let the color of the surface grit vary across a 36-inch shingle. One shingle may have one end darker than the rest, and the next shingle may have the center darker than the rest. The random pattern serves to hide natural wear, scuff marks, and staining as the shingles age. Patterning also relieves the manufacturer of trying to produce a perfectly uniform color.
Patterned shingles are designed to be laid across the roof, but many roofers lay the shingles straight up. It is quicker and easier for them to get on their knees and the bottom of their toes and lay straight up the roof, starting at their base and offset lines. As I said earlier, most roofers have the base and offset lines 34 inches and 28 inches from the rake. They go straight up the side of the roof, using the base and offset lines. They carry the same bundle of shingles right up the roof, pulling shingles from the top of the bundle as they go up.
Laying shingles straight up leads to the “tiger-striping” of the shingles. When the roof is finished, you will see a broken striping effect as you look at the roof from a slight distance. Darker lines angle up the roof.
Laying straight up is also obvious when the roof is a color without a random pattern. Certain-teed makes a white shingle that is pure white. Remember what I said about different production runs being different shades. A home in our area faces away from the main road. The back roof shines a shimmering white except for one cream-white strip rising vertically near the center of the roof. The roof looked as if it were patched the day it was done. It’s surprising how many people have noticed it
My method of laying shingles across the roof breaks up the “tiger-striping.” I stock roofs, breaking the bundles of shingles up as I go. For example, if the section of roof you are going to overlay has an area of ten squares, you know you will need to stock thirty bundles (10 sq. x 3 bundles/sq. = 30 bundles).
Space these bundles evenly on the roof. Tear the paper off the lower bundles on the roof, but leave the upper bundles wrapped until you are ready for them. (A wrapped bundle will withstand unexpected high winds.) Split the bundles in half as you need them and skip the halves across the roof. It takes a few extra minutes, but your finished roof will have a pattern that is absolutely random.
An unscrupulous roofer will try to convince the customer that the manufacturers prescribe laying the shingles straight up the roof. As you know, this is not true. You know about “tiger striping.”
Another problem is that roofers laying the shingles vertically don’t usually butt one vertical course snugly against the previous vertical course. This leaves extra-wide keyways where the vertical courses meet. These extra wide keyways are obvious from the ground.
A more serious problem occurs when the roofer jams the butt ends of the shingles together on vertical courses. When the shingles are jammed, there is no room for the shingles to expand and contract. On a hot day, jammed shingles tend to pucker up into “fish mouths.”
When you finish a section of the roof, there is one thing you should do immediately before the sun seals the tabs down. Have someone stand on the ground and sight directly up the roof. Have them direct you to every “fish mouth” and gently lift the raised tab.
You will find either a raised nail or a little piece of trash holding the shingle up. Either snug the nail down or brush a scrap of trash out of the way so the shingle will seat and seal down. A fish mouth is a weak spot because it gives a high wind a place to start tearing off your new roof.
You can help the person on the ground by standing to the side of the immediate area he is checking and holding the head of your hammer down on the roof as he directs you. The vertical handle of the hammer gives him a reference and helps him tell you which direction to go to find the flaw.
Some roofers who still “hand nail” their roofs don’t make sure their nails are down snug. However, the problem of “fish mouths” is more prevalent with an air gun. Too many roofers don’t take the time and trouble to snug all the nails (staples) down and clean the trash from under the tabs.
CUT RAKE OVERHANGS
If you set the roof up as described earlier in this article, you are going to have one course of shingles overhanging the rake by 2 inches. The longer tabs will overhang the rake by 8 inches. The long tabs are heavy: if you leave them there they will sag over the face of the rake. Sagging weakens the shingles, and high wind will make the overhanging tabs flap and break along the edge of the fascia board. You need to cut some weight off the long tabs. Use your hook knife and cut off 4 or 5 inches. I find it best to cut off the long tabs as I lay the courses up the roof. Giving the long tabs this rough trim removes extra weight and allows your shingles to continue sticking straight out from the rake.
Trim the rakes as you finish each section of the roof. Trimming as you go will keep the overhang from sagging, and you won’t have to worry about trimming the whole roof in the event of a sudden storm.
You need to pop a chalk line to trim the rakes. Start by sitting at the bottom of the rake board. Stick a 25-foot metal tape under the overhanging shingles and butt the end of the tape against the rake board. Begin trimming the shingles back until the metal tape shows you have exactly 1 inch of shingle overhanging the rake. Make a single cut up the roof at this 1-inch mark. Hook the metal nail clip at the end of the chalk line beneath this cut, and lay out your chalk line on the roof. Cut back to the 1-inch mark at the top of the roof then gently lay your chalk line in position. Pull the line tight and pop a chalk line.
As when you cut the rakes off the old roof, each shingle will cover the upper portion of the next course down the roof. There will be no chalk on the top 7 inches of the covered shingle. Simply angle your hook blade back in toward the rake and use the cut edge of the shingle above as your guide. You should angle the blade because the cut you make using the chalk line is the straightest: it’s the cut you want to be the most visible from the ground. When you look up your rake from the ground, it will look as if you cut it with a laser.
Trimming the rakes is one distinctive feature that is easily seen from the ground. There are all kinds of ways to trim a rake. Some roofers won’t take the time to pop a chalk line for their rake. They just use the first joint of their forefinger to measure the overhang as they trim down the roof. The rake edges on roofs done this way look like an alligator chewed them off.
Lightly sweep the roof down. The asphalt in the small scraps tends to melt and make the trash adhere to your new shingles. Don’t try to sweep every bit of loose grit. You will end up breaking loose some of the grit that was still bonded tight. Just get the small scraps and some of the loose grit off the roof.
Sweeping each section (into the gutter) as you go gives the roof a finished appearance and makes the final cleanup much easier.