The process of patching a roof will differ slightly depending on the severity of the damage, the style of roof, and the urgency of the patch. Most importantly, do not allow damaged areas to be unfixed, even for a short period of time. If necessary apply a temporary patch until time allows for a complete repair, but do not leave any leak unattended. Ignoring damaged roof areas, no matter how small, will accelerate your need for added labor, finances, and possibly a new roof. Patches for popular roof materials will follow.
Flat Roof: Using a broom or brush, clean each damaged area carefully until the leak is visible. Often after proper cleaning, further leaks will be exposed. As each leak is exposed, mark it with chalk or tape. Areas that pool up water or areas near seams or the drip-edge flashing commonly leak. Once the leaks are located, apply plastic roof cement to the leak and the surrounding six inches. Immediately after applying the cement, affix fiberglass cloth on top of the wet cement with a putty knife and add a second layer of plastic roof cement. Before covering the patch with gravel, allow it to dry and endure a storm. If the leak originates from a blistered spot on the roof begin the patching process by opening the blister with a utility knife, being careful not to damage the roofing felt below the blister. Open the sliced blister, dry the area, and thoroughly clean it. Apply roofing cement within the blister and close it with galvanized roofing nails. Cover the sealed blister with a layer of roofing cement, making sure to cover the nails.
Shingled Roof: Plan roof repairs during a dry afternoon. This will help the stability of the shingles and the success of the patch. Three common shingle repairs will be discussed below.
1. Replacing shingles: Remove the bottom two roofing nails from the two shingles directly above the damaged shingle (above to the right and above to the left). When removing the roofing nails pry the shingle up about 1/4 in.; then press the shingle down and remove the exposed nails. Once the above nails are removed, carefully pry each of the four nails from the damaged shingle with a pry bar in the same way as described above. After removing the damaged shingle, slide in a new shingle into place and nail the four corners with roofing nails. Cutting around the nails of the damaged shingle may be necessary if the shingles are brittle. If possible, nail into the same holes. This will prevent future leaking. You can also fill the previous holes with roofing cement. When nailing the new shingle down, damage is prevented by using a small board as a nailing surface. Placing some roofing cement under the new shingle will secure it soundly.
2. Curled corners: Apply roofing sealant under each curled corner and place a brick on top of the corner of the shingle for a day or two, letting the sealant dry.
3. Cracked shingles: Apply a thick bead of roofing sealant under the cracked shingle and press down on the shingle. Spread some roofing sealant on top of the crack as well. Often you can gather shingle granules from your gutter or from shaving an extra shingle. Apply these granules to the wet roofing sealant on top of your cracked shingle to hide the patch.