Why Important
Dormers may be part of the original roof design giving daylight to accommodation in the roof space, and are often decorative.
Dormers are also exposed to extremes of weather. They are often physically and visually inaccessible and as a result suffer from a lack of maintenance, which often leads to water penetration problems.
What to look for
Dormers are often built up in masonry off the top of the wallhead, with timber structures behind and pitched roofs, all clad in slates or tiles. Dormers are prone to wind damage and slates and nail fixings can be pulled out.
As dormers interrupt the main roof slope and are complex in shape, there are many junctions between planes and materials which are potential weak points and are prone to failure. Rhones (gutters) are particularly inaccessible, and if unmaintained will rust. Therefore, it can be difficult to re-fix individual slates on dormers.
Some Dormer cheeks (sides) have vertically-hung slates which are traditionally double-nailed (have two nails at the head of the Roof Hip Cheek (side) Window). Others are mostly glazed, so should be treated the same as windows. See Woodwork, doors and windows [Images of Hamilton Square dormers required and then matched to style type listed]
The Georgian style dormers could be rectangular or polygonal and generally have hipped roofs. Examples can be seen in Hamilton Square, opposite the Hamilton Square Underground Station building. (IMAGE HERE)
When to look
It is advised that an annual inspection of the flashings between the dormer and main roof, gutters and apron flashings (the lead flashings below the window cills) is carried out. Inspect after high winds, because the wind can lift or even pull off lead or zinc flashings.
How to fix
Find a good vantage point – even from a neighbour’s flat across the road and take your binoculars! Or find a professional (licenced) Drone Surveyor to take photos.
Avoiding creating problems
Historical background
For Georgian buildings dormers were seldom part of the original design and could be expressly forbidden in the title deeds, but many were introduced soon after the buildings were completed and in order to make good use of the roof space.
There are quite a variety of dormer designs, such as ‘catslide’ dormers, crowsteps, ogee-arched and classical pediments. If a second storey is fitted into the steeply pitched roofs, there can be second row of timber- framed dormers above.
Examples include