A dormer is a roofed structure, often containing a window, that projects vertically beyond the plane of a pitched roof. A dormer window is a form of roof window.

A loft conversion or an attic conversion is the process of transforming an empty attic space or loft into a functional room, typically used as a bedroom, office space, a gym, or storage space. Loft conversions are one of the most popular forms of home improvement in the United Kingdom as a result of their numerous perceived benefits.