Scupper
A scupper is an opening through a parapet wall that allows water to overflow off a flat roof when primary drains are blocked. Required on all parapeted flat roofs.
Ask Chalkline about this →A scupper is an opening or channel through a parapet wall (or similar raised perimeter kerb) that provides an emergency overflow path from a flat or low-pitch roof when primary drainage outlets are blocked. Its purpose is to prevent uncontrolled ponding that could overload the roof structure.
Scuppers are typically set at 150 mm above the finished roof membrane surface: high enough to allow normal drainage via primary outlets, but low enough to limit the maximum ponding depth in a drain-blocked event. The scupper directs overflow water off the roof edge in a controlled location, away from windows and wall openings below.
Where scuppers discharge over the building facade, a purpose-made scupper box or collector with a downpipe is used to protect the wall face from water damage. Sizing follows the same drainage design principles as primary outlets under AS/NZS 3500.3:2018 (verified 2026-05-10).
Also known as: overflow scupper, parapet scupper.
Category: Flat roof drainage / stormwater.
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Last updated: 2026-05-10. Verified: 2026-05-10. Quarterly review for currency.