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Roofing

Parapet

In Plain English

The low wall around the edge of a flat roof that extends above the roof surface.

Definition

A low wall or railing along the edge of a roof, terrace, or balcony, extending above the roofline. Parapets require careful waterproofing detailing at their base (where they meet the roof membrane) and at their tops (coping). They create challenges for roof drainage and must be properly flashed with counterflashing to prevent water infiltration into the wall cavity.

Why It Matters in Bidding

Parapets drive disproportionate cost and risk in roofing bids because the waterproofing, coping, and counterflashing details are labor-intensive and a frequent source of callbacks. Estimators must verify whether the wall, coping cap, and base flashing fall under the roofing scope or the masonry/sheet-metal scope to avoid gaps that surface during buyout or change orders.

Example

An estimator pricing a 20,000 SF flat roof adds linear-foot pricing for parapet base flashing, termination bar, and prefinished metal coping after the takeoff shows 480 LF of parapet wall the original square-foot allowance ignored.

Related Terms

CounterflashingFlashingBuilt-Up Roof (BUR)

Frequently Asked Questions

It depends on the project's scope-of-work split, so estimators should never assume. Base flashing and membrane terminations typically fall to the roofer, while the coping cap may go to a sheet-metal or masonry sub. Clarify the division in an RFI before bid day to prevent a coverage gap during buyout.
Because parapets block water from running off the edge, the design relies on internal drains or through-wall scuppers. Estimators must count scuppers, overflow scuppers, and conductor heads as separate line items, and confirm tapered insulation crickets are included, since these details add material and labor not captured in a flat square-foot rate.
Parapets create multiple transition points where the membrane turns vertical and terminates against coping. Each joint is a potential failure if counterflashing, termination bars, or coping laps are detailed poorly. Pricing quality details and proper sequencing upfront reduces warranty callbacks that erode margin after substantial completion.

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