Building components · Terminations
Parapet
Explains why a parapet creates three exposed surfaces and a junction, all of which have to be resolved together.
Educational reference entry. What this element has to do, and whether any particular arrangement of it is adequate, depends on the whole assembly, the loading, the exposure, local requirements, the manufacturer's instructions and qualified professional design.
Overview
What a parapet is
A parapet is the part of a wall that continues past the roof. It hides the roof edge, and in many buildings it also provides edge protection at roof level.
It creates a particular difficulty: a wall that would normally have a roof over it now has weather on the inner face, the outer face and the top, plus a junction at its base where the roof waterproofing has to turn up and terminate.
Boundaries
How it differs from nearby elements
The distinctions that keep this entry from being a restatement of its neighbours.
- It is not an upstand. An upstand is the turned-up edge of the waterproofing; a parapet is the wall, and the upstand runs up its inner face.
- It is not a coping. The coping caps the parapet and is a published material entry; the parapet is the wall beneath.
- It is not a balustrade. A balustrade is a guarding element that may be open; a parapet is solid wall.
Terminology
Common names and aliases
These names describe the same element. The library keeps one entry per component so that a trade term or a regional name never becomes a second, thinner page.
- parapets
- parapet wall
- parapet upstand
Dependencies
What it depends on
What has to be right elsewhere for this element to do its job.
- How it is capped, since the top is a horizontal exposed surface on what is otherwise a wall.
- How the roof waterproofing turns up its inner face and terminates.
- Where the insulation line runs, since a parapet projects past the roof insulation and is a well-known thermal bridge.
- Movement, because a parapet is exposed on three sides and moves more than the wall below it.
Considerations
Topics that genuinely apply here
Subjects worth discussing about this element. These are discussion topics, never measured values, ratings or performance claims.
Parapets are wetted on both faces and on top, and water entering the top of one has the whole wall below to travel down through.
A parapet continuing past the roof insulation is one of the most common and most significant thermal bridges in a flat-roofed building.
Exposure on three sides means larger temperature and moisture swings than the wall below, and movement provision reflects that.
Parapet failures are frequently traced to the capping or to the junction at the base rather than to the wall itself.
Materials
Commonly formed from
Material families this element is commonly realised in. This states common practice only — it is not a statement that any of these materials suits this component in a particular building, which depends on the whole assembly and on qualified review.
Materials
Commonly incorporates
Materials this element commonly contains as a distinct constituent part, rather than being made of.
Assemblies
Building systems this element is met in
The role this component fills inside each assembly. A role describes what the element does there — it is not a statement that this component suits that system in any particular building.
Junctions
Interfaces this element takes part in
Junctions where the condition between this element and another governs how the construction behaves. These name the junction and the subjects it raises; they are not details, arrangements or approved ways of building.
Parapet Base to Roof Upstand
Where a flat roof meets the wall continuing above it, and where three exposed surfaces converge on one waterproofed corner.
Raises: Moisture · Thermal continuity · Movement · Weathering
Where it is met
Application contexts
Building contexts where this element is commonly encountered. Association is not recommendation: appearing here does not mean the component suits every instance of that context, or any particular one.
- Flat Roof
Clarifications
Commonly misunderstood
- That a parapet is just the wall carried up. The exposure conditions are different, and so are the movement and thermal consequences.
- That damp beneath a parapet means the roof has failed. It very frequently originates at the coping or at the base junction instead.
Conversations
Questions for qualified professionals
Questions worth asking someone with the project in front of them. This page cannot answer them.
- How is the top of the parapet capped, and how does that cap shed water clear of both faces?
- How does the roof waterproofing turn up and terminate on the inner face?
- How is the thermal bridge at the parapet addressed?
- What movement provision exists, given the exposure on three faces?
Go deeper
Related Build Design Hub guides
Planning guidance behind the decisions this element involves.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this element comes up.
What this entry does not do
- No height, capping arrangement, upstand height, insulation detail or movement joint spacing is stated here.
- Parapet design combines weathering, thermal and structural requirements and is a design matter, not a detail to copy.
Terminations & Weathering
The elements where a plane stops, turns up, sheds water or is deliberately interrupted — parapets, upstands, flashings, drips, weeps and movement joints.
Browse all terminations entries →