Box Dormers in Cambridgeshire
Cambridgeshire homeowners come to us for box dormers that are properly detailed at the junctions — because that is where dormers succeed or fail.
Box Dormers — indicative geometry
Box Dormers for Cambridgeshire homes
Most of the dormer work we take on around Cambridgeshire is on Victorian and Edwardian terraces, interwar semi-detached houses and post-war bungalows, where the ridge height and the position of the existing purlins set the limits.
A box dormer is the plainest form there is: two cheeks, a flat or very shallow top, and a flat front. There is nothing clever about it, which is precisely the point — fewer junctions means fewer places to leak, and a shorter programme on site. Most single-room dormers on post-war housing are box dormers whether or not anyone calls them that.
Key specification
| Typical projection | 1.5m – 3.5m wide |
|---|---|
| Depth | 1.8m – 3.0m into the roof |
| Roof finish | GRP, EPDM or felt |
| Cheek finish | Tile-hung, GRP or vertical cladding |
Planning and building control in Cambridgeshire
Rear dormers on houses often sit inside permitted development, but the volume allowance is consumed by any previous loft or rear extension — so we check the planning history for the address before we say yes.
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 Cambridgeshire use us
We would rather tell you at survey that your ridge height will not take what you want than take a deposit and find out in week three.
Book the survey, get the fixed written price, and decide in your own time. Nothing about that process commits you to anything.
Other dormer work in Cambridgeshire
- Full-Width Rear Dormers in Cambridgeshire
- Cat Slide Dormers in Cambridgeshire
- Velux to Dormer Conversions in Cambridgeshire
- uPVC Dormer Windows in Cambridgeshire
- Sash Dormer Windows in Cambridgeshire
- GRP Fibreglass Dormer Roofing in Cambridgeshire
- Flat Roof Dormers in Cambridgeshire
- Hipped Roof Dormers in Cambridgeshire
FAQs
Box Dormers in Cambridgeshire — FAQs
Is scaffolding included in the price?
Yes. Every quotation we issue includes scaffold design, erection, weekly inspection, hire for the programme and dismantling. Scaffold appearing as an extra afterwards is one of the more common complaints about dormer work, so we price it in from the start.
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.
Find out what your roof will take
A free measured survey in Cambridgeshire tells you what is achievable, what it needs, and what it costs — before you commit to anything.