Cat Slide Dormers in County Antrim
We are a dormer specialist, not a general builder who occasionally does roofs — and across County Antrim that focus shows up in the detailing.
Cat Slide Dormers — indicative geometry
Cat Slide Dormers for County Antrim homes
The housing stock around County Antrim runs to Victorian and Edwardian terraces, interwar semi-detached houses and post-war bungalows — so the first question at survey is always which of those you have, because the structure underneath differs completely.
A cat slide (or 'sweeping') dormer lets the main roof plane run on below the dormer sill, so the dormer appears to emerge from the roof rather than to be planted on it. It is a rural and cottage idiom, and it works beautifully on long, low roofs where a box dormer would look brutal. Detailing at the sill and the sweeping valley is the whole job.
Key specification
| Typical width | 1.2m – 3.0m |
|---|---|
| Sweep | Main roof continues below sill line |
| Roof finish | Plain tile, slate or pantile |
| Critical detail | Swept valley and sill flashing |
Planning and building control in County Antrim
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.
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 Antrim use us
One quotation covers scaffold, structure, weatherproofing, glazing, plastering and sign-off. You are not coordinating four trades who each blame the last one.
If you want to know what your roof will actually take, the survey is free and there is no obligation attached to it.
Other dormer work in County Antrim
- Timber Dormer Windows in County Antrim
- Conservation Dormer Windows in County Antrim
- Lead & Zinc Dormer Roofing in County Antrim
- Pitched Roof Dormers in County Antrim
- Shed Dormers in County Antrim
- Box Dormers in County Antrim
- Bungalow Dormer Conversions in County Antrim
- Dormer Window Replacement in County Antrim
FAQs
Cat Slide Dormers in County Antrim — FAQs
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.
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.
Will a dormer add value to my house?
A properly built and signed-off dormer conversion adding a bedroom and bathroom typically returns a meaningful share of its cost in value, and more in areas where floor space is scarce. The building control completion certificate is what makes the space count as habitable floor area on a valuation — without it, surveyors will not include it.
Find out what your roof will take
A free measured survey in County Antrim tells you what is achievable, what it needs, and what it costs — before you commit to anything.