L-Shaped Dormers in Lincolnshire
We design, build and weatherproof l-shaped dormers for homeowners across Lincolnshire, working from first survey through to building control sign-off.
L-Shaped Dormers — indicative geometry
L-Shaped Dormers for Lincolnshire homes
The housing stock around Lincolnshire 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.
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 Lincolnshire
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 Lincolnshire 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.
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 Lincolnshire
FAQs
L-Shaped Dormers in Lincolnshire — FAQs
Do I need planning permission for a dormer window?
Rear dormers on a house often fall under permitted development, provided the dormer is set at least 200mm back from the eaves, sits below the ridge line, uses materials similar in appearance to the existing house, and stays within the volume allowance — 40m³ for a terrace, 50m³ for a semi or detached. Front-facing dormers, flats and maisonettes, listed buildings, conservation areas and any property with an Article 4 direction all need a full planning application. We check the constraints on your specific address before we quote.
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.
What is the best roof covering for a flat dormer?
GRP fibreglass and EPDM rubber are the two we specify most. GRP cures into a single seamless laminate with bonded trims and suits small tops with several upstands. EPDM is a one-piece membrane that copes better with movement on larger spans. Both carry twenty-year guarantees; mineral felt is cheaper but has a materially shorter life.
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.
Can you match my existing roof tiles?
Usually. Most common clay and concrete profiles are still in production or available reclaimed, and we source a match at survey stage so you see it before work starts. Where a discontinued profile cannot be matched exactly, we normally recommend taking tiles from a less visible slope for the dormer and using the closest new match on the hidden elevation.
Find out what your roof will take
A free measured survey in Lincolnshire tells you what is achievable, what it needs, and what it costs — before you commit to anything.