- A dormer window is one which projects from the roof or as an extension of the main windows.
- 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 - as an architectural feature
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.
Dormer- Providing Habitable Space
- 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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