Dormer windows in Bedminster
From the first measured survey to the completion certificate, we run dormer windows and dormer loft conversions projects in Bedminster as a single, managed piece of work.
What we build in Bedminster
Because Bedminster 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.
Whether that is a single flat roof dormer to make a back bedroom usable, or a full-width rear dormer with a bedroom and en-suite, the process is the same: a free measured survey first, a fixed written price second, and nothing else until you have both in front of you.
Planning permission in Bedminster
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.
Bedminster sits in Bristol, and local authority interpretation of the volume allowance does vary — which is why we check the planning history at your specific address rather than assuming the neighbours' dormer sets a precedent.
How the job runs
Design and consent
Measured drawings, elevations and sections. We submit the planning application or lawful development certificate and the building regulations application.
Structure
Ridge beam and floor steels craned or manhandled in, new joists laid, the dormer frame built and sheathed.
Glazing
Windows fitted square, sealed and drained, with escape-compliant opening lights where required.
Survey and feasibility
A specialist measures the roof, checks ridge height, span and structure, and confirms whether you are inside permitted development.
We only do dormers. That sounds like a limitation until you have watched a general builder improvise a back gutter on a wet Thursday. Book the survey, get the fixed written price, and decide in your own time. Nothing about that process commits you to anything.
Popular in Bedminster
Dormer work we are asked for most
Dormer Window Repairs
Leaks, rot, failed flashings, blown units and draughts — diagnosed and put right.
Learn moreHipped Roof Dormers
Three sloping faces instead of a gable — softer, and often easier to get past planning.
Learn moreBox Dormers
A simple squared projection — the workhorse dormer for bedrooms and bathrooms.
Learn moreBungalow Dormer Conversions
Turn a bungalow's roof void into a first floor — often doubling the footprint.
Learn moreuPVC Dormer Windows
Low maintenance, well insulated and the most cost-effective frame for a dormer.
Learn moreConservation Dormer Windows
Heritage-profile dormers and glazing for conservation areas and listed buildings.
Learn moreFAQs
Dormers in Bedminster — FAQs
What happens to my existing loft insulation?
It comes out. Insulation at ceiling-joist level is in the wrong place once the loft is a room — the thermal line moves up to the new roof and dormer build-up. We remove and dispose of the old quilt and insulate the new envelope, which is also what makes the room comfortable to use in August.
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.
Will my roof be open to the weather?
No. The roof is only opened once the scaffold, temporary weather protection and materials are all on site, and the dormer is made weathertight — structure, deck, membrane and temporary glazing — before the crew leaves at the end of the opening-up phase. We do not open a roof on a Friday afternoon.
Can you build a dormer on a bungalow?
Usually yes, and bungalows often give the best results because the spans are wide and there are no party walls. The deciding factor is ridge height: you generally want at least 2.6m from the top of the ceiling joists to the underside of the ridge. We measure this at survey before committing to anything.
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.
Find out what your roof will take
A free measured survey in Bedminster tells you what is achievable, what it needs, and what it costs — before you commit to anything.