Who this guide is for
- Homeowners with flat-roofed or parapet-walled houses
- People seeing damp at the top of an exposed wall
- Renovators adding or renewing a parapet detail
- Anyone briefing a roofer on parapet capping and flashing
Why parapets are vulnerable
A parapet is exposed on the outer face, the inner face and the top, so it is wetted from all sides and has no roof overhang to shelter it. Water entering the top can track down inside the wall and appear far from its source. This exposure is why the capping and flashing matter so much.
Coping and capping the top
The coping or capping caps the top of the parapet and must shed water clear of both faces, usually with a slight fall and a drip detail. A flat or poorly lapped coping lets water sit and seep in. Planning the coping is the heart of keeping a parapet dry.
- Coping should fall and shed water off both faces
- Drip details keep water from running back onto the wall
- Joints in the coping are common leak points
- The coping ties into the roof-edge flashing
Flashing where roof meets wall
Where the flat roof meets the inner face of the parapet, flashing carries the waterproofing up the wall so water cannot get behind. This junction is critical on flat roofs. Plan how the roof membrane and parapet flashing tie together.
Scuppers and drainage
On some parapet roofs, water drains through scuppers in the parapet, which then become deliberate openings that must be detailed against leaks and provide overflow. Coordinating scuppers with the roof drainage and overflow plan is essential. Treat them as part of the drainage system.
Waterproofing and professionals
Parapet capping, flashing and the roof junction are specialist waterproofing work, and the wall top is often a height-access job, so a qualified roofer should design and execute it. Damp at the top of a wall should be assessed rather than guessed at. Requirements vary by location and project.
Parapet planning checklist
- 1Recognise the parapet is exposed on all sides and the top
- 2Plan coping that falls and sheds water off both faces
- 3Include drip details to keep water off the wall
- 4Detail the flashing where roof meets the inner face
- 5Coordinate any scuppers with the roof drainage plan
- 6Address joints in the coping as leak points
- 7Tie the roof membrane and parapet flashing together
- 8Have a roofer design the waterproofing and capping
Common mistakes to avoid
- Treating the coping as a finishing touch rather than a weather detail
- Using a flat coping with no fall or drip
- Ignoring the flashing where roof meets the parapet
- Leaving coping joints as unsealed leak points
- Forgetting scuppers need overflow and leak detailing
- Guessing at parapet damp instead of having it assessed
When to involve a professional
- Have a qualified roofer design the coping, flashing and roof junction
- Treat parapet waterproofing as specialist, safety-relevant work
- Use proper access for the wall top rather than improvising at height
- Have damp at the top of a wall assessed by a professional
- Requirements vary by location and project; verify with your professionals
Frequently asked questions
Questions readers ask about this topic
What is a parapet wall?
A parapet is the part of a wall that rises above the roof line, common on flat-roofed and modern homes. Because it is exposed on both faces and the top with no overhang, it takes weather from every direction and relies on its capping and flashing to stay dry.
What does the coping on a parapet do?
The coping or capping caps the top of the parapet and sheds water clear of both faces, usually with a slight fall and a drip detail. A flat or poorly lapped coping lets water sit and seep in, so it is central to keeping the parapet dry.
Why does damp appear far from the parapet?
Water entering the top or joints of a parapet can track down inside the wall and emerge well away from where it got in. That is why parapet damp should be assessed by a professional rather than guessed at from where it shows.
Are scuppers part of the parapet?
On some parapet roofs, water drains through scuppers, which are deliberate openings in the parapet that must be detailed against leaks and provide overflow. They should be coordinated with the roof drainage and overflow plan as part of the system.
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