Long-lasting repairs to an EPDM roofing system requires the right repair materials and careful prep of the repair area. EPDM roofing membrane is made with synthetic rubber and is not compatible with asphalt-based products. This includes any type of roof cement flashing as well as any asphalt-based roof coating, including aluminum roof coating. These materials will contaminate the EPDM rubber membrane, leading to a more extensive repair.
Patching materials for EPDM roofing are sold as either standard membrane materials that require separate adhesive or as pressure-sensitive materials that have the adhesive pre-applied to the underside of the membrane. Patching materials also are sold in kits that include cleaner, primer, and roller for bonding the patch. These kits can be expensive, but they may include enough material to make several repairs.
Equipment / Tools
- Tape measure
- Shears or utility knife
- Paintbrush or paint roller with medium-nap cover
- All-purpose household cleaner
- EPDM patch material
- EPDM roof primer
- Lap sealant
- Old credit card
Prepare the Roof Surface
The first step in repairing an EPDM roof is to prepare the roof surface to receive the patch. EPDM has carbon contained within the membrane, and as the membrane ages, the sheet develops a carbon film that can be seen if you rub a hand across the sheet. This carbon film, as well as dirt and other oxidation, must be cleaned from the surface to ensure that the patch will stick and perform well over the long-term.
To clean the roof surface, use a cleaner that does not leave a residue. Many manufacturers recommend an all-purpose household cleaner, such as Simple Green or Spic-and-Span. Wash the patch area, cleaning well beyond the area where the patch will be applied. Use cloth rags to remove the oxidation from the surface of the EPDM and to remove all traces of moisture.
Cut the Patch to Size
Measure the patch area. Cut the EPDM patch material so it extends at least 2 inches beyond the damaged area in all directions, using heavy shears or a utility knife. Clip or round off the corners of the patch to remove sharp corners that can be caught and lifted by foot traffic on the roof surface.
Prime the Repair Area
Apply a thin coat of EPDM roofing primer to the membrane surface where the patch is to be applied, using a paintbrush or a paint roller with a medium-nap roller cover. Make sure the primer extends beyond all edges of where the patch will go.
Install the Repair Patch
Methods for installing the patch vary depending on what type of repair kit you have:
Using a pressure-sensitive patch: Remove the paper or film backing from the patch, apply the patch to the roof membrane, and press it down firmly. Roll the patch in multiple directions with a roller to remove any air bubbles and fully bond the patch.
Using a glue-down patch: Apply a single-ply EPDM adhesive to the back of the patch and to the roof surface in the patch area, following the manufacturer's instructions. Allow the adhesive to flash off until it is no longer tacky to the touch. Press the patch onto the roof, then roll it with a steel roller, moving back and forth in multiple directions to remove air bubbles and bond the patch.
- Note: The adhesive must be designed for sealing EPDM to EPDM. Do not use yellow glue designed for sealing EPDM to substrates or insulation board.
Seal the Patch Edges
Apply a heavy bead of EPDM lap sealant around the perimeter of the patch, sealing all edges. Smooth and flatten the sealant with an old credit card or similar plastic tool so the edges are well sealed and the sealant feathers onto the surrounding surface.