L-Shaped 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.
L-Shaped Dormers — indicative geometry
L-Shaped Dormers for County Antrim homes
Most of the dormer work we take on around County Antrim 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.
On a Victorian or Edwardian terrace with a rear outrigger, an L-shaped dormer wraps the main rear slope and the back addition into a single continuous structure. It is the only way to get two bedrooms plus a bathroom out of a narrow London-style terrace loft. The junction between the two arms is where these live or die — it needs a properly designed valley and a single continuous membrane.
Key specification
| Configuration | Main rear dormer + outrigger dormer |
|---|---|
| Typical footprint | 18m² – 30m² gained |
| Critical detail | Valley junction and continuous membrane |
| Structure | Two ridge beams plus valley beam |
Planning and building control in County Antrim
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 Antrim 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 Antrim
- Dormer Window Installation 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
- Eyebrow Dormers in County Antrim
- Bungalow Dormer Conversions in County Antrim
FAQs
L-Shaped Dormers in County Antrim — FAQs
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.
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.
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.