How to Repair a Flat Roof Membrane

Using Standard EPDM

• 1

  Use a razor blade to cut the existing membrane around the damaged area, allowing at least 2 feet on every side. Use a heat gun, if necessary, to melt the old adhesive on the membrane, and then pull it up. Check the quality of the timber underneath to ensure that it is in not rotten or decaying.

• 2

  Use measuring tape to gauge the size of the area that is in need of new membrane. Unroll the EPDM on a hard, flat surface. Use the razor to cut as many pieces as are necessary to fill the space, giving an extra inch or two on each side to ensure there are no large cracks or gaps.

• 3

  Use a paint roller to apply either latex or neoprene liquid adhesive to the underside of the new membrane. Remove any clumping or excess with a trowel. Place the new membrane down on the exposed timber where the old membrane was removed from. Use the razor to trim any edges to ensure the new membrane fits snugly.

• 4

  Seal the edges of the new membrane with the latex or neoprene liquid adhesive and smooth out with the trowel. Allow the adhesive to sit for 20 to 30 minutes. Finally, apply a layer of waterproof mastic sealer to the top of the membrane in order to protect from moisture, leaks and water damage.

Using Liquid EPDM

• 5

  If possible, check the timber underneath the crack or tear to make sure it is not rotten or decaying. Use a razor to cut off any shredding or fringe pieces of membrane along the tear.

• 6

  Pour the liquid EPDM in the crack and smooth it out with the trowel, making sure to remove all air bubbles. Allow 20 to 30 minutes for the EPDM to set.

• 7

  If the liquid EPDM is not also a waterproofing agent, brush a coat of waterproof mastic sealer over the area that was just repaired.