Parapet
A parapet is the short wall continuing past the roof line on a flat or low-pitch roof, where the waterproofing membrane turns up and seals to its inside face.
Ask Chalkline about this →A parapet is the vertical wall continuing past the roof line at the edge of a flat or low-pitch roof. On a membrane flat roof it is the surface the waterproofing turns up and terminates against, and on any roof it carries the coping that throws water clear of the wall below.
What it does on the roof
- Holds the membrane upstand. The waterproofing membrane is dressed up the inside face to form an upstand, sealed at a height set by AS 4654.2.
- Carries the cap detail. The top is finished with coping or a metal cap flashing, with a continuous counter-flashing lapping back over the upstand so wind-driven water cannot get behind it.
- Conceals the roof edge. It hides gutters, plant, and the roof profile from street view, giving the flat-top look common on warehouses, terraces, and modern residential boxes.
Where it shows up
Flat or low-pitch membrane roofs, boundary walls between attached units (where the parapet is often also a fire-separating element), and balconies or terraces with a perimeter wall above the membrane line.
Why the detail matters
A parapet is the most leak-prone edge on a flat roof. The upstand-to-cap detail (membrane up the face, counter-flashing or cap lapping over it, fall on the coping) is what stops water tracking down the inside of the wall. Get the upstand short, the cap fall wrong, or the counter-flashing loose, and the parapet becomes the leak path the whole roof drains through.
Also known as: parapet wall, roof parapet.
Category: Roofing / waterproofing detail.
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See also
Last updated: 2026-05-28. Verified: 2026-05-28. Quarterly review for currency.