Dormer Window Replacement in Dorset
Dorset homeowners come to us for dormer window replacement that are properly detailed at the junctions — because that is where dormers succeed or fail.
Dormer Window Replacement — indicative geometry
Dormer Window Replacement for Dorset homes
Because Dorset is largely Victorian and Edwardian terraces, interwar semi-detached houses and post-war bungalows, the roof pitches and span widths we meet are fairly predictable, and that makes feasibility a quick conversation rather than a guess.
Most dormer windows fail long before the dormer does. Rotten timber sills, blown double-glazed units, seized hinges and perished seals are all replaceable in a day or two without disturbing the cheeks or roof. We survey the surrounding timber first — there is no point putting a new frame into a rotten sub-sill, and that is where a lot of cheap replacements go wrong.
Key specification
| Typical duration | 1–2 days per dormer |
|---|---|
| Scaffolding | Tower or scaffold depending on height |
| Sub-sill check | Timber probed and replaced if soft |
| Glazing upgrade | 1.2 W/m²K or better |
Planning and building control in Dorset
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 Dorset 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.
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 Dorset
FAQs
Dormer Window Replacement in Dorset — 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 Dorset tells you what is achievable, what it needs, and what it costs — before you commit to anything.