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Mansard Roof

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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.

The mansard has four sloping sides, similar to a hip roof but much steeper and extending far down the wall elevation. However, each of the four sides has a double slope. The steep roof creates an additional floor of habitable space 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, near Paris, France. 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 and also known as a "barn roof" 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 technically 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.

A significant difference between the two, for snow loading and water drainage, is that, when seen from above, Gambrel roofs culminate in a long, sharp point at the main roof beam, whereas mansard roofs always form a low-pitched roof.

The mansard style makes maximum use of the interior space of the attic and offers a simple way to add one or more stories to an existing (or new) building without necessarily requiring any masonry or other expensive exterior finishes. Often the decorative potential of the Mansard is exploited through the use of convex or concave curvature and with dormer window surrounds and insets.

In the late-1960s and 1970s, commercial builders became interested in the stylistic and economical elements of the design, adapting the mansard for new residential housing and apartment buildings in many areas of the United States, including Denver and the older suburbs like Lakewood, Golden, Littleton and Aurora.

The outward appearance of a mansard roof has also been adapted as a façade on numerous small commercial buildings. These are not true mansard roofs in most cases; they are actually flat roofs and the sloped façade provides a way to conceal heating, ventilation and air conditioning equipment from persons at ground level.