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.
Dormer window of the Building of Préfecture de police de Paris (île de la Cité)
Gable dormers at Hospices de Beaune in Beaune, France
Pair of hip roof dormer windows on the Howard Memorial Hall, Letchworth
Gable fronted dormer (shallow instance wholly glazed)
Loft conversions in the United Kingdom
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.
A professionally installed loft conversion.
Mobilisation to site, start of dormer extension
Start of dormer conversion. Tiles and felt stripped off
Tiles, felt and wood battens stripped off from inside