uPVC Dormer Windows
Low maintenance, well insulated and the most cost-effective frame for a dormer. Best thermal performance per pound; nothing to paint.
uPVC Dormer Windows — indicative geometry
What a upvc dormer window actually is
Modern multi-chamber uPVC gives excellent U-values, needs no decoration and shrugs off the weather exposure a dormer takes on all four sides. Foiled finishes — anthracite grey, black, cream, woodgrain — have largely killed the old objection that uPVC only comes in white. On a rear dormer that nobody sees from the street, it is the sensible default.
Specification at a glance
| Frame | 70mm or 80mm multi-chamber, steel reinforced |
|---|---|
| U-value | 1.2 W/m²K typical, 0.8 with triple |
| Finishes | White, foiled woodgrain, anthracite, black, cream |
| Opening styles | Casement, tilt-and-turn, top-hung, fixed |
| Maintenance | Wash down only |
| Guarantee | 10 years |
How we build it
One quotation covers scaffold, structure, weatherproofing, glazing, plastering and sign-off. You are not coordinating four trades who each blame the last one. Every upvc dormer windows job runs the same seven stages — survey and feasibility, design and consent, scaffold and protection, structure, weatherproofing, glazing, then finish and sign-off.
Whether you need planning permission or a lawful development certificate depends on the elevation, the volume already used and the local authority's Article 4 position — all of which we confirm before design work starts.
What is included in the price
- Measured survey, structural calculations and full working drawings
- Planning application or lawful development certificate, and the building regulations application
- Scaffold design, erection, weekly inspection, hire and dismantling
- All structure, weatherproofing, flashings, gutters and cladding
- Glazing with escape-compliant opening lights where required
- Building control inspections and your completion certificate
- Waste removal and making good
Where this goes wrong elsewhere
The two failures we are called to fix most often on upvc dormer windows are undersized or incorrectly lapped flashings, and a vapour control layer that stops at the first awkward junction. Neither shows up for a winter or two. Both are cheap to do properly at build stage and expensive to correct afterwards.
Book the survey, get the fixed written price, and decide in your own time. Nothing about that process commits you to anything.
Related work
uPVC Dormer Windows by county
Where we do this work
Specialist teams across 74 counties. Pick your area for local detail, or browse every town.
How a dormer gets built
Seven stages, in this order, every time
The sequence matters. Most dormer problems come from doing one of these out of order — glazing before the flashings, or opening the roof before the materials land.
Survey and feasibility
A specialist measures the roof, checks ridge height, span and structure, and confirms whether you are inside permitted development.
Design and consent
Measured drawings, elevations and sections. We submit the planning application or lawful development certificate and the building regulations application.
Scaffold and protection
Scaffold designed, erected and inspected. Temporary weather protection over the work area before anything is opened.
Structure
Ridge beam and floor steels craned or manhandled in, new joists laid, the dormer frame built and sheathed.
Weatherproofing
Deck, insulation, membrane or lead, cheek cladding, flashings and gutters — the dormer is weathertight from this point.
Glazing
Windows fitted square, sealed and drained, with escape-compliant opening lights where required.
Finish and sign-off
Plaster, electrics, decoration and making good, final building control inspection and your completion certificate.
FAQs
uPVC Dormer Windows — your questions
Why is my dormer leaking?
In our experience the window itself is the cause less than a fifth of the time. Far more often it is the apron flashing at the dormer front, the lead soakers where the cheeks meet the roof slope, the back gutter behind a pitched dormer, or a split at an upstand in the flat covering. Water then tracks along a rafter and appears somewhere else entirely, which is why we trace the path before quoting.
What insulation do dormers need?
Current building regulations want around 0.15–0.18 W/m²K for a new dormer roof and 0.18 W/m²K for the cheeks and front. In practice that is a warm-roof build-up using 100–150mm of PIR insulation above or between the structure, with a continuous vapour control layer on the warm side. Getting the VCL continuous matters more than the insulation thickness.
Do you handle the planning application?
Yes. We prepare measured drawings, elevations and sections, submit the application or the lawful development certificate, and deal with the case officer's queries. On conservation and listed work we also put together the heritage justification the application needs.
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.
Can you convert an existing Velux loft to a dormer?
Yes, and it is usually a shorter job than starting from scratch because the floor, staircase and services already exist. We verify the existing floor structure and any previous building control approval first, then cut and form the dormer into the finished room. Expect the room to be out of use for three to five weeks.
Do you work on listed buildings and in conservation areas?
Yes. That work is detail-led: matching sightlines, glazing bar widths, cill projections and cheek finishes to what survives, and specifying timber, lead and natural slate rather than modern equivalents. We prepare the drawings and heritage statement for listed building consent alongside the planning application.
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.
Find out what your roof will take
A free measured survey tells you what is achievable, what it needs, and what it costs — before you commit to anything.