Dormer Window Replacement in County Down
We are a dormer specialist, not a general builder who occasionally does roofs — and across County Down that focus shows up in the detailing.
Dormer Window Replacement — indicative geometry
Dormer Window Replacement for County Down homes
Most of the dormer work we take on around County Down 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.
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 County Down
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 County Down 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.
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 County Down
FAQs
Dormer Window Replacement in County Down — 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 County Down tells you what is achievable, what it needs, and what it costs — before you commit to anything.