Full-Width Rear Dormers in Devon
We are a dormer specialist, not a general builder who occasionally does roofs — and across Devon that focus shows up in the detailing.
Full-Width Rear Dormers — indicative geometry
Full-Width Rear Dormers for Devon homes
Because Devon is largely cob and stone cottages, Victorian villas and a large stock of retirement bungalows, the roof pitches and span widths we meet are fairly predictable, and that makes feasibility a quick conversation rather than a guess.
A full-width rear dormer runs from party wall to party wall, squaring off the entire rear slope. On a standard terrace or semi it typically converts 12–18m² of crawl space into full-height room — enough for a double bedroom and an en-suite. Set back 200mm from the eaves and 500mm below the ridge, it usually falls inside permitted development on a house that has not been extended before.
Key specification
| Typical projection | 4.0m – 8.0m wide |
|---|---|
| Set-back | 200mm from eaves, 500mm below ridge |
| Structure | Steel ridge beam plus floor steels |
| Roof finish | GRP, EPDM or single-ply membrane |
Planning and building control in Devon
Getting the consent route right at the start saves months. We establish whether it is permitted development, a lawful development certificate or a full application on the first visit.
Building regulations approval is separate and always required. We submit the application, book the inspections around the programme and hand you the completion certificate at the end — the document a buyer's surveyor will ask to see.
Why homeowners in Devon use us
The completion certificate is part of the deliverable, not an afterthought. It is the document that makes the space count when you come to sell.
Send us the address and roughly what you are hoping to gain, and we will come back with a realistic answer rather than an optimistic one.
Other dormer work in Devon
FAQs
Full-Width Rear Dormers in Devon — FAQs
How wide can a dormer be?
Structurally, as wide as the roof — full-width rear dormers regularly run six to eight metres, carried on a steel ridge beam. The limits are usually planning volume allowances and the setbacks needed at eaves and ridge, rather than what can be built.
What guarantees do you provide?
Structural work carries a ten-year guarantee, GRP and EPDM flat roofing twenty years, windows ten years on frames and sealed units, and lead and zinc work is covered for workmanship for ten years. You also receive the building control completion certificate, which is the document that actually matters when you sell.
Can you build a dormer in winter?
Yes, with adjustments. Temporary weather protection over the scaffold lets structural work continue in most conditions. GRP roofing needs dry conditions above about 5°C to cure properly, so in a cold spell we either sequence it differently or specify EPDM, which is unaffected.
How much does a dormer window cost?
A single flat roof dormer typically runs from around £9,000 to £20,000 supplied and fitted, depending on width, cladding finish and access. A full-width rear dormer on a semi is usually £28,000 to £45,000, and a complete dormer loft conversion including stairs, insulation, plaster and building control sign-off is more commonly £40,000 to £70,000. Our online guide-price tool gives you an indicative range in about a minute.
Does a dormer need building regulations approval?
Yes, always — permitted development covers planning, not building control. A dormer needs approval for structure, thermal performance under Part L, fire escape and protected route under Part B, and stairs under Part K if a staircase is involved. We handle the application, the inspections and the completion certificate.
Find out what your roof will take
A free measured survey in Devon tells you what is achievable, what it needs, and what it costs — before you commit to anything.