History of the Mansard Roof

A mansard roof is a four-sided roof with two slopes on each side: a steep lower slope, often pierced by dormer windows, and a shallow upper slope that may be almost flat. It turns the roof into an extra habitable storey, the garret, while keeping the overall height down.

Origins

The earliest known example is usually credited to Pierre Lescot on part of the Louvre in Paris around 1550. The French architect François Mansart (1598-1666) used the form so heavily in the early 17th century that it took his name, but he did not invent it. His great-nephew Jules Hardouin-Mansart (1646-1708) continued the tradition.

Why Paris adopted it

A popular story says mansards were built to avoid a tax on windows or storeys. This is unlikely: the French window tax dates from 1798, long after Mansart's death, and did not exempt mansard windows. A better explanation is a 1783 Paris rule limiting building height to 20 m (66 ft) measured to the cornice, which left space inside the roof uncounted. A 1902 revision allowed three or four storeys within the roof.

Second Empire boom

Under Napoleon III's Second Empire (1852-1870) and Haussmann's rebuilding of Paris from the 1850s, mansards became standard on apartment blocks, with zinc and slate coverings. The "Second Empire" style spread to civic buildings, hotels and railway stations in Europe and North America. In the United States and Canada, especially New England, it appeared on houses and mansions.

Fire risk

Timber-framed mansards could be dangerous. In the Great Boston Fire of 1872, flames spread from the wooden mansard roof of the first warehouse along neighbouring rooftops; 776 buildings were destroyed.

Later uses

• The 1916 New York City zoning rules suited mansards because of their setback requirements.
• Soviet rules until 1981 limited dachas to one storey but did not count roof space, so many dachas have mansards.
• In the 1960s and 1970s flat-topped mansards were used to hide rooftop mechanical equipment.

Mansard or gambrel?

A mansard slopes on all four sides (a curb hip roof). A gambrel slopes on two sides only, like many North American barns. French and German usage often does not distinguish them, and "mansarde" can mean the attic room itself.