How to Patch a Hot Tar Roof

Favored for their durability, hot tar and gravel roofs are a cost-efficient flat roofing option. Tar and gravel roofs are known as “built-up roofs” because they consist of alternating layers of hot tar and waterproof membranes, with which the top layer is coated with a bed of gravel for fire and weather resistance. Although relatively long-lasting, built-up roofs are susceptible to leaks and hence require occasional patching. Leaks in hot tar roofs often occur when gravel shifts or wears away and exposes the underlying membrane to weather conditions. Promptly patch a hot tar and gravel roof to prevent water damage to the home’s interiors.

Things You'll Need

Pry bar
Utility knife
Nylon scrub brush
6-inch-wide reinforcement fabric

Scissors
Rubber gloves
Plastic roof cement
Gravel

Instructions

- 1
  Uncover the leaking portion of the tar and gravel roof. Using a pry bar, scrape all gravel off the damaged area to reveal the cracked roof membrane. Expose 3 1/2 inches of membrane along both sides of the crack.
- 2
  Cut through both ends of the crack with a utility knife to prevent the crack from extending. Make both cuts about 3 inches long.
- 3
  Scrub the cracked roof membrane with a nylon-bristled scrub brush to loosen and remove foreign material, such as dust and grime. Clean the damaged area well.
- 4
  Lay 6-inch-wide reinforcement fabric along the crack. Cut the pre-measured reinforcement fabric with scissors, and then place the fabric aside.
- 5
  Gear up in rubber gloves to avoid exposing your hands to plastic roof cement. Using your gloved hands, spread the cement 1/4 inch thick over the crack. Extend the cement 3 1/2 inches beyond both sides of the crack, rubbing the cement into the crack.
- 6
  Cover the wet bed of cement with the pre-cut fabric. Press and rub the fabric into the cement using your gloved hands.
- 7
  Apply a 1/8-inch-thick skim coat of plastic cement over the patch to fully embed the fabric. As previously, apply the cement with your gloved hands and extend the cement 3 1/2 inches beyond both sides of the crack.
- 8
  Spread an even layer of gravel over the wet cement to thoroughly conceal the patch. Use the same type of gravel as on the rest of the roof.
- 9
  Let the patched tar and gravel roof cure for 72 hours.

How to Extend a Roof Overhang

DIY Roofing Estimate

Roof Repairs