Parapet

A parapet is a barrier that is an upward extension of a wall at the edge of a roof, terrace, balcony, walkway or other structure. The word comes ultimately from the Italian parapetto (parare 'to cover/defend' and petto 'chest/breast'). Where extending above a roof, a parapet may simply be the portion of an exterior wall that continues above the edge 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. Parapets were originally used to defend buildings from military attack, but today they are primarily used as guard rails, to conceal rooftop equipment, reduce wind loads on the roof, and to prevent the spread of fires. 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, or 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. The Mirror Wall at Sigiriya, Sri Lanka built between 477 and 495 AD is one of the few surviving protective parapet walls from antiquity. Built onto the side of Sigiriya Rock it ran for a distance of approximately 250 meters and provided protection from inclement weather. Only about one hundred metres of this wall exists today, but brick debris and grooves on the rock face along the western side of the rock clearly show where the rest of this wall once stood. Parapets surrounding roofs are common in London. This dates from the Building Act of 1707 which banned projecting wooden eaves in the cities of Westminster and London as a fire risk. Instead an 18-inch brick parapet was required, with the roof set behind.