Parapet
Contents |
[edit] What is a parapet?
A parapet is typically the uppermost reaches of a wall that extends above the roof level and provides a degree of protection to roof, gutters, balconies and walkways of houses, churches, castles, apartment blocks, commercial and other buildings. It may be constructed from brick, stone, concrete, timber or even glass. A parapet may also prevent fire spreading to a roof and provide a degree of protection from a sudden and potentially fatal fall.
On a pitched roof, a parapet may only exist where a wall rises above the eaves, which is generally the lowest point of the roof as it terminates above a gutter; this point forms a convenient valley into which a gutter can be placed.
The top of a parapet will usually be terminated by some form of capping or coping in brick, stone, or concrete, or even sheet metal, such as lead, zinc or steel.
Cappings are usually flush with the sides of the wall while copings extend from the face. Tradiitonally, copings would extend by around 50mm or more on either side of the wall to provide weather protection to the area below; they would also be throated (ie incorporate a continuous semi-circular recess called a 'drip') to convey water away from the wall to reduce the risk of damp penetration.
[edit] Problems with brick parapets
Two of the most common problems encounteerd with brick parapets are bowing, where the parapet develops an unsightly lean to one side, usually the roof side; and cracking of the brickwork. If either of these becomes excessive, rebuilding the parapet may be necessary.
The reasons for such problems can be complex but they usually involve:
One side of the parapet getting more sunshine (heat) and rain (and therefore more saturation) than the other side. This may cause a degree of differential movement which will be exacerbated as, unlike the brickwork at the lower reaches which is constrained by the weight of the brickwork above, the brickwork in a parapet has far less constraint and therefore can move more freely. Differential weathering mechanisms will be heightened when one side of the parapet faces north and the other faces south.
Cracking of the brickwork in a parapet may be the result of insufficient movement joint provision to absorb any expansion. Movement joints in parapets (and freestanding walls) should be more generous than those in a structure's walls because the lack of restraint in the parapet can amplify the effects of movement.
NB High Speed Rail (Crewe – Manchester) Environmental Statement, Glossary, abbreviations and references, published by the Department for Transport in 2022, defines a parapet as: ‘A low wall along the edge of a structure (e.g. a bridge), to protect people from falling.’
[edit] Related articles on Designing Buildings
- Aircrete blocks.
- Bartizan.
- Blockwork.
- Cavity tray.
- Cavity wall.
- Damp-proof course.
- Defects in brickwork
- Efflorescence.
- Mortar.
- Perpend.
- Pointing.
- Rainwater head.
- Spalling.
- Treating brickwork with sealant or water repellent.
- Types of bricks.
[edit] External references
Featured articles and news
SELECT three-point plan for action issued to MSPs
Call for Scottish regulation, green skills and recognition of electrotechnical industry as part of a manifesto for Scottish Parliamentary elections.
UCEM becomes the University of the Built Environment
Major milestone in its 106-year history, follows recent merger with London School of Architecture (LSE).
Professional practical experience for Architects in training
The long process to transform the nature of education and professional practical experience in the Architecture profession following recent reports.
A people-first approach to retrofit
Moving away from the destructive paradigm of fabric-first.
International Electrician Day, 10 June 2025
Celebrating the role of electrical engineers from André-Marie Amperè, today and for the future.
New guide for clients launched at Houses of Parliament
'There has never been a more important time for clients to step up and ...ask the right questions'
The impact of recycled slate tiles
Innovation across the decades.
EPC changes for existing buildings
Changes and their context as the new RdSAP methodology comes into use from 15 June.
Skills England publishes Sector skills needs assessments
Priority areas relating to the built environment highlighted and described in brief.
BSRIA HVAC Market Watch - May 2025 Edition
Heat Pump Market Outlook: Policy, Performance & Refrigerant Trends for 2025–2028.
Committing to EDI in construction with CIOB
Built Environment professional bodies deepen commitment to EDI with two new signatories: CIAT and CICES.
Government Grenfell progress report at a glance
Line by line recomendation overview, with links to more details.
An engaging and lively review of his professional life.
Sustainable heating for listed buildings
A problem that needs to be approached intelligently.
50th Golden anniversary ECA Edmundson apprentice award
Deadline for entries has been extended to Friday 27 June, so don't miss out!
CIAT at the London Festival of Architecture
Designing for Everyone: Breaking Barriers in Inclusive Architecture.
Mixed reactions to apprenticeship and skills reform 2025
A 'welcome shift' for some and a 'backwards step' for others.
Comments
[edit] To make a comment about this article, click 'Add a comment' above. Separate your comments from any existing comments by inserting a horizontal line.