Dormer roofs: repair, re-cover and what it costs
Dormers concentrate every awkward roofing detail into a couple of square metres: a small flat top, two cheeks, an abutment to the main slope and usually a window.
Where dormers leak
Almost always at junctions — the cheek-to-main-roof abutment, the top-to-cheek trim, and around the window frame. The flat top membrane itself is rarely the first thing to fail.
Re-covering the top
EPDM in a single piece is the usual answer for a small dormer top because there are no field seams. GRP is the alternative where a rigid, walked-on finish matters.
Cheeks and cladding
Cheeks can be tile-hung, slate-hung, leadwork or clad. Matching the existing finish matters visually far more on a dormer than on a hidden flat roof, because it's the part everyone sees from the street.
Cost drivers
Size is a small factor; access and detail count for more. A rear dormer over a single-storey extension may need a bridged scaffold. Lead-heavy detailing on a period property costs more than a simple modern box dormer.
Doing it once
If the window is old and the top is being stripped anyway, replacing the window at the same time is far cheaper than a second visit with the same access costs.
FAQs
Small, isolated damage on an otherwise sound membrane can be patched. If the membrane is felt with failing seams, patching tends to just move the leak.
Many dormers fall under permitted development, but conservation areas and previously altered properties often don't. Repairs and like-for-like re-covers usually don't require it.
Typically one to three days on site once access is up, depending on how much of the cheeks and detailing is being renewed.
Related reading
More on costs & budgeting and the jobs that usually come with it.
- Roof cost by house type: terrace, semi, detached and bungalowCosts & budgeting
- Roof window installation: what it costs and what's involvedCosts & budgeting
- Flat roof cost: GRP versus EPDM versus feltCosts & budgeting
- Dry-fix vs mortar-bedded ridgesComparisons
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