EPDM rubber roofs most often leak at the seams, where two sheets are joined with adhesive or seam tape. Over time, heat, ponding water, movement and poor cleaning at install cause the seam to peel open. Flashing at walls, curbs, drains and pipes is the next most common spot. Seam repairs use cleaned rubber, primer and new seam tape or cover strips.
Why seams fail
- Old adhesive: Older roofs used liquid adhesive, which breaks down faster than modern seam tape.
- Poor prep: Seams that were not cleaned and primed never stuck fully.
- Ponding water: Water sitting on a seam for days wears it down. See water ponding on a flat roof.
- Heat and movement: The rubber moves with temperature swings, pulling at the seam.
- Foot traffic: Walking on seams, especially near HVAC units, loosens them.
Signs of seam failure
- Edges of a seam lifting or wrinkling
- Gaps you can slide a finger or card into
- Dirt lines inside a seam
- Stains inside that line up with a seam
- Bubbles or fishmouths along the seam
Other EPDM leak spots
Flashing where the roof turns up a wall or parapet, around HVAC curbs, at drains and scuppers, and around pipe penetrations. Punctures from dropped tools, hail or tree limbs are also common. EPDM shrinks a little as it ages, which can pull flashing away from walls at the edges.
How seams are repaired
Clean
The rubber on both sides of the seam is cleaned of dirt and old adhesive.
Prime
EPDM primer is applied so the tape can bond.
Tape or strip
New seam tape or a wide cover strip goes over the seam, rolled down firmly.
Seal edges
Lap sealant is applied along the edges of the patch.
Roof cement and tar do not bond to EPDM and can damage it. Repairs should use products made for EPDM. See flat roof leak repair and flat roof leak repair cost.
Where we see EPDM in Pine Bluff
Downtown commercial buildings behind brick parapets, strip centers, churches, and home additions and porches with low slopes. Many older downtown roofs are rubber or modified bitumen laid over older built-up roofs. See commercial roof leak repair.
How long does EPDM last?
Often 20 to 25 years when installed well and kept up. Seams and flashing need checking every year or two, and after storms. See how long roofs last in Arkansas.
Repair, recover or replace?
A roof with a few loose seams is a repair. A roof with seams failing everywhere, shrinkage pulling flashing loose all around, or wet insulation underneath may need a new membrane. We can check whether the insulation under the rubber is wet, which is key to the decision.
What to do while you wait for a repair
Keep drains clear so water does not sit on the seam, and keep foot traffic off the area. Inside, catch the drip and move anything that can be damaged. A strip of EPDM seam tape on a clean, dry, primed seam can hold for a while if you are comfortable on a flat roof.
How to tell EPDM from TPO
EPDM is usually black, sometimes white, and feels like an inner tube. TPO is usually white or light gray, feels more like plastic, and its seams are heat-welded rather than taped. The repair method is different, so it helps to know which you have.
How long do EPDM seams last?
Taped seams on a well-installed roof often last many years. Older glued seams fail sooner.
Can I patch EPDM myself?
Small patches with an EPDM patch kit on a clean, dry, primed surface can work. Use products made for EPDM.
Does tar work on rubber roofs?
No. It does not bond and can damage the membrane.
Can a rubber roof be coated?
Yes, with coatings made for EPDM, after seams and flashing are repaired.