Takeoff & Estimating — Roofing, Envelope & Finishes

EPDM Roofing

A rubber single-ply roof membrane, taken off in squares.

Quick Answer

EPDM roofing is a single-ply synthetic rubber membrane, ethylene propylene diene terpolymer, used on low-slope commercial roofs. It is installed fully adhered, mechanically attached or ballasted. Estimators measure the roof and flashing area in squares of 100 SF and add laps, waste and accessories.

The Full Picture

EPDM is a single-ply rubber membrane that the EPDM Roofing Association describes as made from polymers and oils with an additive for UV resistance. It is used on low-slope roofs, which NRCA's glossary describes as roofs with slopes of 3:12 or less, though OSHA's fall protection rule uses a different cut-off of 4 in 12 for its own purposes. Black membranes contain carbon black, while white membranes use titanium dioxide, which is a color choice that affects price and sometimes the energy code compliance path.

The attachment method defines the system and the price. Per the same association, ballasted EPDM is loose-laid over insulation in panels up to 50 x 200 ft and held down with stone or concrete pavers, and ballasted systems account for about 35 percent of EPDM installations. Mechanically attached systems fasten through the membrane or along side laps with plates or batten strips. Fully adhered panels, up to 30 x 100 ft, are bonded to insulation that is itself secured by fasteners, plates or adhesives. Ballast needs structural capacity, and mechanical or adhesive systems need compatible substrates, so the structural and roof-plan notes matter for pricing.

Roofing is measured in squares, where 1 SQ = 100 SF. The membrane quantity is the field area plus flashing to parapets, curbs and penetrations, with side and end laps and waste added as a percentage that varies by system and roof geometry. Items carried separately include insulation and cover board, ballast or fasteners, adhesive, seam tape or splice, pipe boots, curbs, edge metal and coping, walkway pads, and drains and sumps. Warranty-driven details can add scope.

The documents are the roof plan, roof details, wall sections at parapets and the roofing specification in Division 07. MasterFormat uses section 07 53 23 for ethylene-propylene-diene-monomer roofing. Typical misses are leaving out base flashing height at parapets, treating a ballasted roof like a bare membrane without the stone or paver quantity, and not reading whether the spec requires a specific manufacturer's system warranty.

Real Examples

→Worked takeoff: membrane squares: A roof is 100 ft x 60 ft, so the field is 6,000 SF. The parapet perimeter is 2 x (100 + 60) = 320 LF, and base flashing runs 2 ft up the wall, so flashing area is 320 x 2 = 640 SF. Total membrane area is 6,000 + 640 = 6,640 SF, or 66.4 SQ. With an assumed 5% for laps and waste, 66.4 x 1.05 = 69.72, which rounds to 70 SQ.

→Comparing attachment methods: The same roof is bid three ways. Ballasted needs a ballast quantity and a structural check, mechanically attached needs a fastener and plate count by zone, and fully adhered needs adhesive coverage. The membrane squares are similar, but the accessory lines and labor differ, so the estimator prices them as separate systems.

→Accessories: A roof has 4 drains, 2 vent pipes and 2 curbs. The estimator counts them in EA, since each needs a boot, a flashing or a patch that the square count does not capture.

Common Misconceptions

People assume: EPDM is always black and loose-laid.

Actually: The EPDM Roofing Association describes black and white membranes and three attachment methods: ballasted, mechanically attached and fully adhered. The spec decides which one applies.

People assume: Roof squares include only the roof surface.

Actually: Flashing up parapets, curbs and walls adds to the membrane area, and laps and waste add more, so a plan-area square count alone runs short.

Does MeltPlan Solve This?

Partially — adjacent

Roof area, parapet lengths and counts of drains and penetrations come off the plans, and MeltPlan's takeoff service pulls them with AI and has US-based experienced estimators review and adjust them. Attachment method, warranty requirements, laps and waste stay with your estimating team.

Get roof areas and penetrations measured →

Frequently Asked Questions

What does EPDM stand for?

EPDM stands for ethylene propylene diene terpolymer, a synthetic rubber used as a single-ply roof membrane for low-slope roofs.

How is EPDM roofing measured?

In squares of 100 SF, covering the field area plus flashing, with laps and waste added. Accessories such as drains, curbs and edge metal are counted or measured separately.

What is the difference between ballasted and fully adhered EPDM?

Ballasted EPDM is loose-laid and held down by stone or pavers, while fully adhered EPDM is bonded to the substrate. Mechanically attached systems are fastened with plates or batten strips.

Where is EPDM specified?

In Division 07, under the single-ply roofing section, 07 53 23, along with the roof plan and detail sheets.