Dormer Window | Architectural Construction

A dormer window is a structural element in a building which are constructed on the sloping roofs. Dormer Windows protrude from the plane of the sloping surface of the roof.

Dormers - as an architectural feature
  • A dormer window maybe constructed during the construction of the building or could be an addition to create a habitable space where the height of the pitched roof is very high.
  • As the name “Dormer Window” suggests, it a window set in a dormer and hence termed as Dormer Window.
  • Like skylights, dormer windows are used as a source of light and ventilation but unlike skylights they are used to provide habitable space in the pitched roof construction…

There are various types of Dormer Window Construction:

  • Gable fronted dormer: the front of the dormer rises to a point at the ridge of the dormer roof. Also known as a dog-house dormer.
  • Hipped roof dormer: the roof slopes back from front of structure to a point farther back.
  • Flat roof dormer: the roof of the dormer is flat.
  • Shed dormer: A dormer (window) whose eave line is parallel to the main roof eave line. Shed dormers can provide more attic space and head room than gable dormers, but cannot be the same pitch as the main roof and may therefore require different roof sheeting. Often used in gable-roofed homes, a shed dormer has a single-planed roof, pitched at a shallower angle than the main roof.
  • Wall Dormer: A dormer whose face is coplanar¬†with the face of the wall below, breaking the line at the cornice of the building.
  • Link Dormer A large dormer that houses a chimney or joins one part of a roof to another.
  • It is used to provide daylighting within the roof space when it is used as a room. It also serves as an architectural feature of interest.
  • Dormers are useful in Bungalow construction for providing additional habitable rooms with the normal roof structure.
  • The building regulations state that the ceiling height of the room must be atleast 2.3m, not less than half the area of the room measured at a height of 1.5m above floor level.
Velux Type Window is similar to Dormer Window
  • The roof covering of the dormer is of the same material as the main roof and both pitched and flat dormers covered with tiles, slates and lead are used.
  • To form the opening in the roof, trimming spars are used on either side and an upper and lower trimmer are jointed to the trimming spar.
  • A window frame forming the front of the dormer and having posts and head with a sill rests on the lower trimmer which has studs beneath it for internal lining fibreboard and skimmed plasterboard.
  • The sides of the dormer have a head jointed to that of the window frame and the trimming spar, studs at the checks are covered externally with boarding, felt and nibblers vertical tile hanging.
  • These tiles are laid to the normal 63mm lap to match the main roof, although a lap of 38mm is sufficient for vertical tiling.
  • Concealed lead soakers are used at the junction of the cheeks and the main roof.
  • The hog-back ridge tiles are slightly tilted at the ends of the ridge and at the roof junction, a lead saddle is placed directly beneath the ridge tile and carried up and over the batten on the main roof slope so as to form a water proof joint at this place.
  • The dormer roof blends into the major roof with a swept valley.

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