How to Repair Tar Roofing

Scrape the gravel off the leaking portion of the tar roof using a flat bar. Remove gravel from 4 inches on either side of the crack, as well, being careful not to puncture the underlying roof membrane. Scrape off gravel until you discover the end of the crack and fully expose the damaged roof membrane.

Make a 3-inch long horizontal cut through the roof membrane at the end of the crack using a utility knife. The slice prevents the crack from spreading. In addition, drive a roofing nail into the roof membrane on either side of the crack using a hammer. Securing the roof membrane to the underlying decking also inhibits the crack from spreading.

Sweep the cracked membrane with a broom to clean the area. Remove all grime particles to ensure the patch adequately bonds.

Lay 6-inch wide polyester reinforcement fabric directly over the entire crack, making sure the fabric extends 3 inches past the crack on either side. Cut the fabric where the crack ends, and then set the fabric aside for later use. Pre-cutting the fabric before you apply the roof cement prevents an inconvenient mess.

Put on rubber gloves and then use your hand to scoop pre-mixed plastic roof cement out of its container. Immediately spread the cement over the entire crack and the horizontal cut you created earlier. Make the cement layer 1/8 to 1/4-inch thick and extend it 3 1/2 inches onto either side of the crack.

Cover the wet cement bed with the pre-cut fabric reinforcement. Gently press the fabric into the cement using a trowel.

Smear a 1/8-inch coat of fresh cement over the fabric reinforcement using your gloved hands. Use the trowel to smooth the cement’s surface so that it’s flat. Don't let the cement cure yet.

Sprinkle loose gravel over the wet cement bed to protect the repair from ultraviolet rays, which deteriorate roof cement. Thoroughly cover the roofing cement with the gravel so that the repair blends in with the surrounding gravel on the roof.