The addition of a dormer window is often included as part of a loft conversion. Dormer windows are not allowed on roofs facing the street. The roof of the dormer window has to be lower than the main house roof.
The Borough Design Guide states on page 57 that the dormer window has to be set “within the main roof by being set back from both the eaves line and sides of the roof”
The Borough Design Guide goes on to say “ Dormers should relate to the design of the existing building in terms of roof form, materials, positioning and window proportions”
A recent application for a very large dormer which replaced most of the existing roof was refused. ACER pointed out that, in addition to being unsightly and not in keeping, such dormers have large windows allowing overlooking into previously private areas of neighbouring gardens.
It was also pointed out that a smaller dormer set further away from the roof edges still benefit s loft conversions.