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Roofingaka: rubber roofingaka: rubber membraneaka: EPDM membrane

EPDM

In Plain English

A durable rubber roofing membrane used on flat or low-slope roofs — the black rubber roof common on commercial buildings.

Definition

Ethylene propylene diene terpolymer — a durable synthetic rubber membrane used as a single-ply roofing material for low-slope applications. EPDM is available in black or white, in thicknesses from 45 to 90 mils, and can be installed using ballasted, mechanically attached, or fully adhered methods. It is valued for its long service life, flexibility in cold temperatures, and resistance to UV radiation.

Why It Matters in Bidding

EPDM is one of the common low-slope membrane choices, so estimators must price the specified attachment method because ballasted, mechanically attached, and fully adhered systems carry very different labor, adhesive, and fastener costs. Membrane thickness and color also affect price and code compliance, and accurate flashing and detail takeoff at penetrations is where EPDM bids most often win or lose margin.

Example

Bidding a flat commercial reroof, an estimator confirms the spec calls for fully adhered 60-mil black EPDM, takes off the field membrane, adhesive, and termination bar, then prices pipe boots and curb flashings at every rooftop penetration.

Related Terms

Single-Ply MembraneThermoplastic Polyolefin (TPO)FlashingVapor Barrier

Frequently Asked Questions

Ballasted systems are loose-laid and weighted with stone, lowering membrane labor but adding ballast and structural load. Mechanically attached systems use fasteners and plates along seams. Fully adhered systems bond the membrane with adhesive, raising material and labor cost but improving wind performance. Estimators must price the exact method the specification requires.
EPDM commonly comes in 45, 60, and 90 mil. Thicker membranes cost more but resist punctures and often carry longer warranties, so the spec or warranty requirement dictates the choice. Bidding a thinner membrane than specified produces a non-responsive number, while over-specifying needlessly inflates the price.
The flat field of an EPDM roof is fast and predictable, but penetrations, curbs, drains, parapets, and transitions require labor-intensive flashing details. Under-counting these in takeoff is the most common way EPDM bids lose margin, since each detail consumes disproportionate labor and accessory material relative to the field area.

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