Mansard Roof

A mansard roof is a hipped roof with a double slope on each of its four sides. The lower slope is very steep, sometimes nearly vertical and sometimes curved, and the upper slope is shallow and may be barely visible from the street. The steep lower slope creates almost a full storey of habitable space within the roof, typically lit by dormer windows. The horizontal line where the two slopes meet is the curb, and mansards and gambrels are both classed as curb roofs.

History

The earliest known example is on part of the Louvre in Paris, built by Pierre Lescot around 1550. The form takes its name from the French architect François Mansart (1598-1666), who did not invent it but used it extensively in the early 17th century; his great-nephew Jules Hardouin-Mansart continued the tradition.

The mansard became fashionable again during the French Second Empire (1852-1870) and Baron Haussmann's rebuilding of Paris from the 1850s. A popular story holds that mansards were built to avoid taxes on storeys or windows; the window tax dates from 1798 and did not exempt mansard windows, and a more plausible reason is that Paris height limits were measured to the cornice, so space within the roof did not count.

In the United States and Canada, the "Second Empire" style spread to public buildings, hotels, railway stations and houses from about the 1860s. In the 1960s and 1970s, flat-topped "neo-mansard" walls were used on commercial buildings, often to hide rooftop equipment.

Mansard versus gambrel

Both have two pitches per side. A mansard is sloped on all four sides (a curb hip roof), while a gambrel is sloped on two sides only and has gable ends (a curb gable roof). In France and Germany, "mansard" can refer to both forms and also to the attic room itself.

Construction and maintenance

The steep lower slopes are usually clad in slate, shingles, tiles or metal, and the shallow upper slope may need a membrane. The junctions at the curb and around numerous dormers need careful flashing. Mansards are popular in UK loft conversions and terrace extensions because they add space within planning limits.