- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 06 Feb 2019
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.
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.
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.
 Related articles on Designing Buildings Wiki
- Aircrete blocks.
- Cavity tray.
- Cavity wall.
- Damp-proof course.
- Defects in brickwork
- Treating brickwork with sealant or water repellent.
- Types of bricks.
 External references
Featured articles and news
Built to defend British waters, only to serve as pirate radio stations later.
Wellbeing to influence mix of home and office based working.
An introduction to cobotics.
Survey reports on outlook for the engineering sector.
A simple path to possible error avoidance.
Construction + technology = ConTech.
New low and high tech tools enter the marketplace.
Report looks at mental health in the built environment.
Radiant wall heating method to control rising damp.
What future infrastructure provision might look like.
Highlighting the health benefits of home improvement.
Pavilions for music, entertainment, and leisure. Book review.
Broadening our understanding of Dublin’s chequered social history.
The charm of London's Cabmen's shelters.
Future Weather Files research tool looking for feedback.
Exploring the Colour Rendering Index.
Why it's important to find out what went wrong.