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Patching Membrane Roofing

One modern way to waterproof large flat roofs is to cap them with gigantic elastomer membrane sheets made from rolls of ethylene propylene diene monomer (EPDM) or other rubber materials. The rolls come in standard sizes: 100 feet long by 10, 15, or 20 feet wide. You may have to hire a roofer licensed by the EPDM manufacturer to repair such a roof. But patching a leak is not difficult. “Rubber” roofing, or modified-bitumen roofing, comes in 4-foot-wide rolls. Pros weld it in place using a large torch. It also can be applied using roofing cement. Often a roof’s life can be extended by brushing on reflective-fibered roof coating with a push broom.

Tools: Brush, scissors, putty knife, steel roller, caulking gun.

1. Apply splice adhesive. Wash the deck around the leak with mild detergent and water. Rinse with fresh water, then wash with “splice wash” to prepare the surface. Using a stiff brush, apply “splice adhesive,” which resembles contact cement, to the prepared area of the roof.

2. Cut a round patch. Cut a round patch of EPDM rubber 4 inches larger in diameter than the damaged area.

3. Apply the patch. Apply splice adhesive to the patch and let the adhesive dry to the touch. Once it’s dry, place the patch carefully—it cannot be slid—and press it into place.

4. Roll the patch. Roll the adhered patch with a 2-inch steel roller. If you cannot find a 2-inch roller, rent a linoleum roller or use a piece of steel pipe.

5. Apply lap sealant. Wait 30 minutes to let the adhesive volatiles escape. Then using a caulking gun, apply lap sealant to seal the edges of the patch. Use a putty knife to flatten the sealant so water cannot collect and puddle.

Repairing Roll and Built-Up Roofing

Roll and built-up roofing usually are applied to nearly flat roofs, which are easy to work on. (However, avoid walking on them more than you have to.) A smaller roof may be covered with roll roofing, made of essentially the same material as asphalt shingles. Black tar roofs are installed by pros, using a large kettle of hot tar. Sometimes gravel is added. “Rubber” (modified-bitumen) roofing is replacing the hot tar. After you’ve slit a blister open, look inside for traces of moisture. Moisture means water has crept under the roofing—usually from defective flashing nearby —or possibly from a hole or a crack in the membrane.

Tools: Whisk broom, putty knife, utility knife, hammer.

Patch a gravel roof. If your roof is topped with gravel or crushed stones, carefully brush them away from the damaged area with a whisk broom. Clean out small cracks, pack them with roofing cement, then feather out more cement for about 3 inches on each side. Sprinkle the patch with gravel.

Slice a blister. Slice open blisters and work the cement inside. Then fasten down the blister edges by driving in roofing nails along each side of the incision. Top off all repairs with a patch that is much larger than the damaged area. Cement it, drive nails, and apply more cement.

1. To patch a damaged section, cut out the old roofing. Replace any extensively blistered or buckling sections. Cut out the old roofing with a utility knife and scrape away the old cement.

2. Fill in with a patch. Trim a new piece of roofing for a snug fit, then nail and cement it in place. Apply enough cement to lap all sides by 3 inches.

3. Cover with a larger patch. Press a second, larger patch into the cement; nail and seal it too. Double-patching makes a strong, watertight, long-lasting repair. Regravel as necessary.

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