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A parapet is a wall-like barrier at the edge of a roof, terrace, balcony or other structure. Where extending above a roof, it may simply be the portion of an exterior wall that continues above the line of the roof surface, or may be a continuation of a vertical feature beneath the roof such as a fire wall or party wall.

Building parapets

The word comes ultimately from the Italian parapetto (parare = to cover/defend and petto =breast). The German term Brustwehr has the same significance.

Parapets may be plain, embattled, perforated or panelled, which are not mutually exclusive terms.
  • Plain parapets are upward extensions of the wall, sometimes with a coping at the top and corbel below.
  • Embattled parapets may be panelled, but are pierced, if not purely as stylistic device, for the discharge of defensive projectiles.
  • Perforated parapets are pierced in various designs such as circles, trefoils, quatrefoils.
  • Panelled parapets are ornamented by a series of panels, either oblong or square, and more or less enriched, but not perforated. These are common in the Decorated and Perpendicular periods.


Parapet roofs

A pub with a parapet hiding the sloping roof
Parapets surrounding roofs are extremely common in Londonmarker. This dates from the Building Act of 1707 which banned projecting wooden eaves in the cities of Westminstermarker and Londonmarker as a fire risk. Instead an 18-inch brick parapet was required, with the roof set behind. This was continued in many Georgian houses, as it gave the appearance of a flat roof which accorded with the desire for classical proportions.

Fire Wall parapets

Many firewalls are required to have a parapet, a portion of the wall extending above the roof. The parapet is required to be as fire resistant as the lower wall. It is required to extend at least 30" above the roof. If the roof slopes at a rate of 2 in 12 or greater (16.7-percent slope), the parapet shall extend to the same height as any portion of the roof within a fire separation distance where protection of wall openings is required, but in no case shall the height be less than 30 inches (762mm). Exterior walls that require to be fire protected are often required to have a parapet, but there are exceptions. *note* If the roofing material is combustible, it must stop 18" minimum from the top of the wall.

Bridge parapets

Parapets on bridges and other highway structures (such as retaining walls) prevent users from falling off where there is a drop. They may also be meant to restrict views, to prevent rubbish passing below, and to act as noise barriers.

Bridge parapets may be made from any material, but structural steel, aluminium, timber and reinforced concrete are common. They may be of solid or framed construction.

In European standards, parapets are defined as a sub-category of "vehicle restraint systems" or "pedestrian restraint systems".

See also



References

  1. Ching, Francis D. K. (1995). A Visual Dictionary of Architecture. Van Nostrand Reinhold Company, ISBN 0-442-02462-2. p. 266
  2. "NC Building State Building Code: Building Code", page 90.,January,2009
  3. Jefferis,Smith,Spence:"Commercial Materials & Construction Detailing", page 145.Thompson,December,2007


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