The average do-it-yourself homeowner can reroof a house. All you need are the correct tools, materials and techniques. The time needed for the reroofing depends completely on the size and scope of the job, but set aside at least two rain-free days for completion.
Remove the old roof by tearing off the shingles, using a flat shovel. The flat shovel is perfect for getting beneath the shingles and removing them from the roof decking. The shingle nails will be the most difficult to remove with the shovel. Just continue to push the shovel across the nails until they release. Drive any remaining nails into the decking using a hammer.
Replace any damaged or rotten plywood. Measure the thickness of the roof decking and replace with the same thickness of material. Remove the damaged material by marking an area directly over the centre of the rafters framing to the left and right of the damage and 4 inches above and below. For example, if the rotted area on your roof is 8 inches around, then find the roofing rafters to the left of the rot and to the right of the rot and make a mark over the centre of those studs, then make a mark 4 inches above and below the rot. Square the marks and cut the section away, using a circular saw. Replace the plywood with a new patch.
Estimate the amount of shingles for your roof replacement. Shingles come in bundles of roughly 30 shingles. Three bundles equal one square of shingles, which equals a 10-by-10-foot area (100 square feet). Measure the length and the width of your roof and multiply those numbers to get a total square footage to be roofed. Divide that number by 100--total square feet in one square of shingles--and you have the number of squares of shingles needed to reroof your house. To determine the numbers of bundles, just multiply the squares by three--numbers of bundles in one square.
Cover the entire roof with felt paper using felt nails. Line up the first sheet of felt paper at the bottom of the roof, keeping the bottom edge of the felt square with the bottom of the roof decking. Use a razor knife to cut the paper once you reach the end of the roof, and begin again above the prior sheet by overlapping the next sheet by 6 inches. The felt paper has reference lines printed on the face to help you line up your felt overlaps.
Snap the first chalk line 12 inches off of the bottom of your roof decking, and repeat every 6 inches thereafter. Have a helper hold the line on one side of the roof while you hold the other end, and then snap the line.
Shingles are usually 12 inches wide and 36 inches long. They have three tabs that are 12 inches by 6 inches and then a solid 6-inch connecting section. The first shingle will be installed upside down where the tabs are facing the top of the roof. Thereafter the shingles will face down, overlap and be staggered halfway. Place the nails of the shingle above the shingle tabs, one in each tab.