Flat roof drainage isn’t optional—it’s the system that protects the building. Two common approaches are scuppers and internal drains. Each has strengths, and the right choice depends on roof design and maintenance access.
What is a scupper?
A scupper is an opening through a parapet wall that lets water exit the roof. Water then drops into a downspout or a collector head.
Scupper advantages
- Simple, visible, and easy to inspect
- Less risk of hidden internal pipe leaks
- Can be paired with overflow scuppers for storm safety
Scupper drawbacks
- Water discharge can stain walls if not detailed well
- Gutters/downspouts still need maintenance
What is an internal drain?
Internal drains collect roof water and route it through plumbing inside the building. They often include strainers and require routine cleaning.
Internal drain advantages
- Cleaner exterior appearance (no scupper discharge on walls)
- Can handle large roof areas when designed correctly
Internal drain drawbacks
- Clogs can cause rapid ponding if not maintained
- Leaks in internal piping can be harder to detect
Overflow strategy (important)
Regardless of drainage type, good designs include an overflow path (secondary scuppers, overflow drains, or emergency routes) so water can’t rise high enough to enter the building.
Maintenance checklist
- Clean strainers and remove debris after storms
- Verify water flows freely to the outlet
- Inspect seams and penetrations near drains (high stress zones)
Next step
If you’re planning a low-slope roof upgrade, start with flat roofing and then request a documented evaluation via contact. If ponding is already visible, read our ponding water guide.