Mansard roof

A mansard or mansard roof (also called French roof or curb roof) is a multi-sided gambrel-style hip roof characterised by two slopes on each of its sides, with the lower slope at a steeper angle than the upper, and often punctured by dormer windows. The steep roofline and windows allow for additional floors of habitable space (a garret), and reduce the overall height of the roof for a given number of habitable storeys. 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 popularised 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 (France, Germany and elsewhere) also means the attic or 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).

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. A significant difference between the two, for snow loading and water drainage, is that, when seen from above, gambrel roofs culminate in a long crease at the main ridge beam, whereas mansard roofs form a rectangular shaped crease, outlined by the curb beams, with a low-pitched roof inside this rectangle.^{[citation needed]}

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.

In France and Germany, no distinction is made between gambrels and mansards – they are both called "mansards". In the French language, mansarde can be a term for the style of roof, or for the garret living space, or attic, directly within it.

The mansard style makes maximum use of the interior space of the attic and offers a simple way to add one or more storeys to an existing (or new) building without necessarily requiring any masonry. Often the decorative potential of the mansard is exploited through the use of convex or concave curvature and with elaborate dormer window surrounds.^{[citation needed]}

One frequently seen explanation for the popularity of the mansard style is that it served as a method of tax avoidance. One such example of this claim, from the 1914 book How to Make a Country Place, reads, "Monsieur Mansard is said to have circumvented that senseless window tax of France by adapting the windowed roof that bears his name." This is improbable in many respects: Mansart was a profligate spender of his clients' money, and while a French window tax did exist, it was enacted in 1798, 132 years after Mansart's death, and did not exempt mansard windows.