Dormer

A dormer is a structural element of a building that protrudes from the plane of a sloping roof surface. Dormers are used, either in original construction or as later additions, to create usable space in the roof of a building by adding headroom and usually also by enabling addition of windows.

Often conflated with the term "dormer", a dormer window is a window set into the dormer. Like skylights, dormer windows are a source of light and ventilation for top floors, but unlike skylights (which are parallel to the roof surface) they also increase the amount of headroom in the room and allow for more usable space.

A blind dormer or false dormer is a dormer that can only be seen from the outside of the house: it is roofed on the inside, and does not provide any extra space or light. These are often used to make the house appear more impressive.

A dormer is often one of the primary elements of a loft conversion.

Origin

Dormer is derived from the french dormir, meaning to sleep or from Latin, dormitorium, meaning a place of sleeping. Dormer windows date their origin to 17th-century Paris and are attributed to French architect Francois Mansart, who introduced the Mansard style roof.