French roof

A mansard or mansard roof (also called a French roof or curb roof) is a four-sided gambrel-style hip roof characterized by two slopes on each of its sides with the lower slope, punctured by dormer windows, at a steeper angle than the upper. The steep roof with windows creates an additional floor of habitable space (a garret), and reduces the overall height of the roof for a given number of habitable stories. The upper slope of the roof may not be visible from street level when viewed from close proximity to the building.

The earliest known example of a mansard roof is credited to Pierre Lescot on part of the Louvre built around 1550. This roof design was popularized in the early 17th century by François Mansart (1598–1666), an accomplished architect of the French Baroque period. It became especially fashionable during the Second French Empire (1852–1870) of Napoléon III.Mansard in Europe also means the attic (garret) space itself, not just the roof shape and is often used in Europe to mean a gambrel roof.

Two distinct traits of the mansard roof – steep sides and a double pitch – sometimes lead to it being confused with other roof types. Since the upper slope of a mansard roof is rarely visible from the ground, a conventional single-plane roof with steep sides may be misidentified as a mansard roof. The gambrel roof style, commonly seen in barns in North America, is a close cousin of the mansard. Both mansard and gambrel roofs fall under the general classification of "curb roofs" (a pitched roof that slopes away from the ridge in two successive planes). However, the mansard is a curb hip roof, with slopes on all sides of the building, and the gambrel is a curb gable roof, with slopes on only two sides. (The curb is a horizontal, heavy timber directly under the intersection of the two roof surfaces.) French roof is often used as a synonym for a mansard but is also defined as an American variation of a mansard with the lower pitches nearly vertical and larger in proportion to the upper pitches.

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