Quick definition
Ethylene propylene diene monomer: a synthetic rubber single-ply membrane, traditionally black, with seams joined by tape or adhesive.
EPDM is the black "rubber roof" on many flat roofs. It has been used on low-slope buildings since the 1960s, longer than most other single-ply membranes.
What is EPDM?
EPDM (ethylene propylene diene monomer) is a synthetic rubber single-ply membrane. It is usually black, with white versions made for reflectivity. It comes in large sheets, reinforced or non-reinforced, in thicknesses such as 45, 60 and 90 mil.
How is an EPDM roof installed?
| Attachment | How it works |
|---|---|
| Fully adhered | Bonded to the insulation or cover board with adhesive |
| Mechanically attached | Fastened along seams or with plates |
| Ballasted | Laid loose and held down with stone or pavers |
Because EPDM is a thermoset, its seams can't be heat-welded. They are joined with seam tape and primer, or with adhesive. The large sheet sizes mean fewer seams than many other membranes.
What are the pros and cons of EPDM?
Strengths
- A long track record on low-slope roofs.
- Stays flexible in cold weather.
- Large sheets mean fewer seams.
- Relatively simple to repair.
- Black EPDM absorbs heat, which matters in hot climates.
- Seams are the most common failure point if taping or priming is poor.
- The membrane can shrink over time, pulling at flashings and edges.
- Punctures from foot traffic or debris.
Where is EPDM used?
EPDM is used on commercial and industrial low-slope roofs, and on flat roof sections and porches of homes. Black EPDM is especially common in colder climates.
EPDM vs TPO
| EPDM | TPO | |
|---|---|---|
| Material | Synthetic rubber (thermoset) | Thermoplastic |
| Usual color | Black | White |
| Seams | Taped or glued | Heat-welded |
| Best known for | Track record, flexibility | Reflectivity, welded seams |
What it means for you
What EPDM means for homeowners
EPDM is a common, repairable choice for flat roofs and porches. In hot areas, ask about white EPDM or a reflective coating to reduce heat.
Frequently asked questions
Sources
- EPDM manufacturer product data and installation instructions. Technical Reference.
Tier 1 authority 路 manufacturer - The NRCA Roofing Manual: Membrane Roof Systems. NRCA.
Tier 2 authority 路 industry - SPRI single-ply roofing technical resources. SPRI.
Tier 2 authority 路 industry