EPDM Roofing

Also known as rubber roofing · EPDM membrane · ethylene propylene diene monomer

Synthetic rubber single-ply membrane, usually black, joined with seam tapes or adhesives, and installed ballasted, mechanically attached or fully adhered.

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EPDM (ethylene propylene diene monomer) roofing is a thermoset synthetic rubber membrane. Because it is vulcanised, it cannot be heat-welded; seams and flashings are made with primers and seam tapes or adhesives. Its saturated polymer backbone gives it strong resistance to ozone, ultraviolet light and weathering.

Inside a flat roof

Composition

The EPDM polymer is roughly half of a typical roofing compound. Carbon black (for reinforcement, UV screening and the black colour), processing oils (for low-temperature flexibility), antioxidants, antiozonants and curing agents make up much of the rest. White EPDM uses titanium dioxide instead. Properly formulated EPDM remains elastic to around minus 40 C (minus 40 F).

History

EPDM entered the US commercial roofing market in the 1960s and spread widely in the 1980s, helped by bitumen price rises in the 1970s energy crisis and labour shortages. Roofs installed in the 1970s are reported to be still performing. In the 1980s factory seam tapes replaced liquid seam adhesives, reducing dependence on workmanship; self-adhering flashing accessories followed. EPDM is used worldwide, including large markets in North America and Europe; in New Zealand a related butyl rubber membrane is common.

Sheets

Standard thicknesses are 45 mil (1.1 mm) and 60 mil (1.5 mm); 75 to 100 mil (1.9 to 2.5 mm) sheets are made for higher puncture resistance. Sheets are available in widths from about 1.4 m (54 in) to 15 m (50 ft) and lengths up to about 61 m (200 ft), so large roofs need few seams. Both non-reinforced and scrim-reinforced sheets are made.

Attachment

Ballasted: loose-laid and held by stone or pavers.
Mechanically attached: fasteners and plates in strips or at points.
Fully adhered: bonded with contact or water-based adhesive, or fleece-backed sheets in adhesive.

Considerations

EPDM degrades in contact with bituminous materials, so separation layers or compatible products are needed when it is used over or beside bitumen. It does not contaminate rainwater runoff, which matters for rainwater harvesting.