EPDM Rubber Roofing: Installation, Seams, Flashing and Repair
8 step by step guides
EPDM is a single layer of synthetic rubber, sold in rolls up to 20 feet wide or more, used on flat and low slope roofs. It is flexible in the cold, does not need a flame to install, and has very few seams on a small roof, which is why it is a popular choice for decks, garages, additions and mobile homes. Its weak points are not the field of the roof. They are the seams, corners, penetrations and edges, where a rubber sheet has to be cut, folded and taped.
Start with EPDM rubber roofing explained for thicknesses and attachment methods, then how to prep a roof deck for EPDM, because adhered rubber is only as good as the surface under it. The main install is in how to install a fully adhered EPDM roof, and how to seam EPDM with seam tape covers the joint that most leaks trace back to.
Rubber roofing in the Fraser Valley has one big practical constraint: adhesives and primers need dry surfaces and mild temperatures, and the wet season gives you fewer good days than you would like. These guides explain the method, the limits and the failure modes, so you can do a small repair with confidence or judge a quote for a full roof. If you are still deciding between systems, see how to choose a flat roof membrane.
EPDM Rubber Roofing Guides
- Guide 1EPDM Rubber Roofing ExplainedEPDM is a single-ply synthetic rubber roofing membrane, usually 45 or 60 mil thick, sold in wide rolls so a small roof can have no seams in the field. It is fully adhered with bonding adhesive, mechanically attached with bars and fasteners, or held down with ballast. Seams are joined with 3 inch splice tape. It commonly lasts 20 to 30 years when flashed well.Advanced1 to 2 days for a small flat roof
- Guide 2How to Prep a Roof Deck for EPDMTo prep a deck for EPDM, repair rot and loose sheathing, confirm the slope to drains, fasten any insulation and cover board, sweep and clean the surface, remove nails and sharp edges, and check that it is dry and within the adhesive's temperature range, commonly about 5 degrees Celsius or higher. Unroll the membrane and let it relax for at least 30 minutes before gluing.AdvancedHalf a day to 1 day
- Guide 3How to Install a Fully Adhered EPDM RoofTo install a fully adhered EPDM roof, unroll the sheet and let it relax, fold it back in half, apply bonding adhesive to the deck and the underside of the membrane, wait until the adhesive is tacky and does not transfer to a dry finger, then roll the sheet into the adhesive without wrinkles and broom it down. Work in sections, and keep adhesive off the seam area.Advanced1 day for a small roof
- Guide 4How to Seam EPDM With Seam TapeTo seam EPDM, overlap the sheets at least 3 inches, fold the top sheet back, clean both surfaces, apply primer to both and let it dry to a slight tack, lay 3 inch splice tape on the lower sheet, then roll the top sheet down onto it, peel the release film and roll the seam hard with a hand roller. Cover every T-joint with a patch of tape-backed membrane.AdvancedAbout 1 hour per 50 feet of seam
- Guide 5How to Flash Inside and Outside Corners on EPDMFlash an EPDM inside corner by adhering the sheet up the wall with slack at the corner, folding the extra rubber into a neat flap, and covering it with a pre-formed inside corner or an uncured flashing patch laid with primer and splice tape. Flash an outside corner with a formed piece or a stretched uncured patch. Run flashings at least 8 inches above the roof and terminate the top.Advanced20 to 40 minutes per corner
- Guide 6How to Flash Pipes on EPDMTo flash a pipe on EPDM, cut the field membrane to the pipe, slide a pre-molded EPDM pipe boot over it with its flange lying flat, prime and splice-tape the flange to the membrane with at least a 3 inch lap all round, then seal the top with a stainless hose clamp and a bead of sealant. Use a field-fabricated flashing or a pitch pocket only when no boot fits.Advanced20 to 45 minutes per pipe
- Guide 7How to Terminate EPDM at Edges and WallsTerminate EPDM at a wall with a termination bar fastened through the membrane every 6 to 12 inches, a bead of sealant along the top edge, and counter flashing, siding or coping over it. At a roof edge, adhere the membrane to a drip edge or gravel stop flange with splice tape and cover strip. Keep the perimeter well secured, because wind uplift starts at edges.Advanced1 to 3 hours per 50 feet of edge
- Guide 8How to Repair an EPDM RoofTo repair EPDM, find the leak, scrub the area with a scrubbing pad and the manufacturer's cleaner until the rubber is clean and dull, apply primer, and cover the damage with a patch of cured EPDM or cover tape that extends at least 3 inches past it in every direction, with rounded corners. Roll it firmly. Do not use asphalt roof cement, which attacks rubber.Advanced1 to 3 hours per repair
Also on this site
EPDM Rubber Roofing: Common Questions
What is an EPDM roof?
An EPDM roof is a single ply of ethylene propylene diene monomer rubber, usually 45 or 60 mil thick, laid over a flat or low slope roof deck. It is adhered, mechanically fastened or held down with ballast. Seams are joined with tape or adhesive, and corners, pipes and edges are flashed with extra rubber or pre-formed pieces.
How long does an EPDM roof last?
A properly installed EPDM roof commonly lasts 20 to 30 years. Life depends on the thickness, how well the seams and flashings were made, ponding water, foot traffic and exposure. Most early failures are at seams, corners and penetrations rather than in the sheet itself, so the workmanship in those details matters more than the brand.
Can you install EPDM in cold or wet weather?
Only within the limits on the adhesive and primer you are using. Many bonding adhesives and primers need a dry surface and a temperature of about 5 degrees Celsius or higher, and some water-based adhesives can be damaged by freezing. Rain, dew and frost on the deck or sheet stop the bond from forming, so wait for a dry window.
Is EPDM better than torch-on roofing?
Neither is better in every case. EPDM is installed without a flame, is quick on simple roofs and stays flexible in the cold. Torch-on is a thicker, layered system that resists foot traffic and punctures better but needs trained crews and fire precautions. The right choice depends on the roof shape, traffic, budget and who will maintain it.
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