As your roof ages, it can become prone to leaking. This not only can accelerate the damage to the roof itself, but also the water leaking into your home can cause other problems, such as damaging drywall, rot and causing the growth of mold and mildew. The majority of leaks occur in areas where there are holes cut into the roof for objects such as vents and pipes. Identifying the location of the leak enables you to know what repairs you need to make.
Determine the Location of the Leak
Examine the roof shingles and look for any spots where the shingles are discolored, or where the roof sags.
Go inside the attic and examine the underside of the sheathing and the rafters. Look for any damp spots or water stains on the wood, or signs of mold growth. Check the insulation in between the floor joists for signs of water damage as well. If you notice mold or water stains in one area, that's the area where the leak is located.
Soak the roof with a garden hose to try to locate the leak. Begin in areas where there is a hole cut into the roof, such as around a vent pipe or skylight. Run the water over the joint for several minutes while an assistant stands inside the house underneath the area where you're applying the water to watch for leaks. Move on to the valleys where different sections of the roof meet at an angle, and finally the main sections of the roof.
Using a pry bar, lift the undamaged shingles in the area surrounding the shingles that are damaged to be able to remove the shingles in the damaged area.
Remove the shingles in the damaged area by lifting them up with the pry bar and taking them off of the roof. Begin at the top of the damaged area and work toward the bottom.
Examine the sheathing where you removed the shingles. If it's damaged, remove the old sheathing and nail new sheathing to the roof rafters to replace it with galvanized nails. Sheathing usually consists of 3/4-inch plywood or oriented strand board (OSB).
Cover the new sheathing with strips of roofing paper. Begin laying the paper at the bottom of the sheathing, and work toward the top. Slide the edges of the roofing paper underneath the shingles surrounding the damaged area, and overlap the different rows of paper by 1 inch as you lay them. Staple them to the sheathing every 6 to 8 inches with a hammer stapler.
Lay the first course of shingles into place along the bottom of the area being repaired. Align the new shingles with the existing shingles in that row, and nail them to the roof by driving in three evenly-spaced roofing nails placed 1 inch above the tabs.
Continue laying new shingles to finish covering the area being repaired. When you get to the last row, slide the top edge of the shingles underneath the bottom of the shingles in the row above them. This prevents water from seeping underneath the top edge of the new shingles.
Nail down the shingles you loosened around the area that was damaged.
Vents and Pipes
Loosen the shingles around the roof vent or pipe with the pry bar.
Remove the boot around the vent pipe, or the roof vent, from the roof. If it's screwed into place, back the screws out with a drill; if it's nailed into place, pry it off the roof with the pry bar.
Apply a thick bead of roofing cement around the vent pipe or the hole for the roof vent.
Place the new boot for the vent pipe or the new roof vent into position. Attach it to the roof with galvanized screws or galvanized roofing nails.
Nail down the loose shingles around the vent pipe or roof vent with roofing nails.