The Mansard roof, named for the 17th-century French Renaissance architect François Mansart, is the distinguishing characteristic of Second Empire style. The Mansard roof is a double-pitched roof with a steep lower slope. There are usually dormer windows set into the lower slope and molded cornices at the top and bottom of the slope. There may also be cresting along the roof line.
Many Second Empire houses have a square or rectangular tower, which is usually centered on the front façade. The tower also has a Mansard roof, with a small round window or dormer on each side.
Beneath the distinctive roofline, Second Empire houses are very similar to Italianate houses. They often have brackets beneath the eaves. Decorative window and door enframements are similar to Italianate examples, as are porch details.