A mansard roof (also known as a French roof) is a four-sided gambrel-style roof with two slopes on every side, with the lower slope being much steeper than the upper slope. It’s a style that was popular in the mid-1800s in France and the United States. The Louvre Museum in Paris is probably the most well-known example of a mansard roof. Obviously, it’s a roof style that is no longer being used in modern-day construction.