Dormer roof repairs and replacements across Amersham.
Dormer windows are everywhere in the Chilterns — bungalow loft conversions, 1970s semis, period properties with rear dormers. Almost all of them have a small flat roof on top, and that flat roof is usually the first part of the house to develop a leak.
We repair and replace dormer flat roofs across Amersham and the surrounding villages.
Call 01494 702 599 for a free survey.
Why dormer roofs cause problems
Dormer flat roofs are particularly leak-prone for a few reasons:
- Small and exposed. They stick up above the main roofline and catch the full force of wind and rain.
- Lots of detail work. The junction between the dormer cheeks, the main roof, and the flat roof on top creates multiple flashings — each one is a potential leak point.
- Often forgotten. Because you can’t see the dormer roof from ground level, problems go unnoticed until water appears on the bedroom ceiling.
- Awkward access. They’re high up and often hard to reach without scaffolding, which means they don’t get inspected regularly.
Common dormer roof problems
Felt failure
Most older dormer roofs in Amersham have a felt covering. After 15–20 years the felt cracks, splits, and lets water in — especially at the cheek flashings where the flat roof meets the vertical sides of the dormer.
Lead flashing failure
The lead flashing where the dormer meets the main roof is a critical waterproofing detail. If the lead cracks, lifts, or the mortar pointing above it falls out, water gets behind the flashing and into the bedroom below.
Cheek cladding deterioration
The vertical sides (cheeks) of the dormer are often clad in tile hanging, render, or timber. If the cladding cracks or the sealant behind it fails, water tracks down and finds its way in.
Ponding water
Dormer flat roofs are small, which means even a slight error in the fall creates ponding. Standing water on a small felt roof accelerates every other problem.
Repair or replace?
Most dormer flat roof repairs are straightforward — re-dress the lead, patch the felt, re-seal the cheek flashings. Takes a few hours.
If the felt is at end of life, we’ll recommend a full re-cover. Dormer roofs are small enough that a full EPDM or GRP replacement is usually under £1,500 — and it solves the problem for 25–30 years.
What it costs
| Type of work | Typical price |
|---|---|
| Lead flashing repair | £150–£400 |
| Felt patch repair | £200–£500 |
| Full dormer re-cover (felt) | £600–£1,200 |
| Full dormer re-cover (EPDM) | £800–£1,500 |
| Full dormer re-cover (GRP) | £1,000–£1,800 |
| Cheek re-cladding | £400–£1,000 |
Do I need scaffolding?
For most dormer roof repairs — yes, unfortunately. Dormers are at roof height and usually can’t be safely reached from a ladder alone. We arrange scaffolding as part of the job and include the cost in the quote. For a standard rear dormer, scaffolding typically adds £300–£600.
If the dormer is accessible from a flat roof below (common on single-storey rear extensions), we can sometimes avoid scaffolding altogether.
Common questions
How do I know if my dormer roof is leaking?
The first sign is usually a damp patch on the bedroom ceiling directly below the dormer, or water marks on the wall where the dormer meets the main roof. If you see damp around a dormer window, it’s almost always the roof or flashings rather than the window itself.
Can you match the existing cheek tiles?
Usually, yes. For common tile types we can source matching replacements. For unusual or discontinued tiles, we may suggest a full re-clad of the cheeks for a uniform finish.
How long does a dormer roof replacement take?
One day for the roof covering, plus scaffolding erection (usually the day before). Total disruption is about two days.
Where we cover
We repair and replace dormer roofs across Amersham, Old Amersham, Little Chalfont, Chalfont St Giles, Chalfont St Peter, Great Missenden, Chesham, Beaconsfield, Penn, Holmer Green, and Hazlemere.
Get a free quote
Phone: 01494 702 599
Email: info@amershamroofers.co.uk