GS Renovation converts lofts in Borough, working on the bay-fronted Victorian and Edwardian terraces set back from the busier SE1 frontages near Borough Market and the South Bank. Where a house still has its rear closet wing, an L-shaped dormer is usually the most space for the money, and we run the steel, the consents and the sign-off together.
L-shaped dormers over SE1 closet wings
The standard Borough terrace has a main roof running front to back and a lower rear closet wing set to one side. An L-shaped dormer wraps the two, giving a double bedroom under the main ridge and a bathroom or dressing area over the wing, which is why it beats a plain rear dormer on this house type. It costs more to build, indicatively £55,000 to £80,000 against roughly £45,000 to £65,000 for a straight rear dormer, on indicative London ranges for 2026.
Not every SE1 house still has the wing, and some have lost it to a previous rear extension. Where it is gone, a straight rear dormer or, on a shallow roof with generous height, a rooflight conversion at roughly £30,000 to £45,000 may be all the structure supports. We measure ridge height first. Below about 2.2m you are into lowering ceilings on the floor beneath or raising the roof, and both change the budget and the planning position considerably.
Southwark planning and building regulations in SE1
Much of central Borough falls within conservation areas, and permitted development for roof extensions is withdrawn inside them. Where your street is not designated, a rear dormer on a terrace can sit within the 40 cubic metre volume allowance if it stays behind the roof plane, matches materials and uses obscure glazing to any side window. Southwark Council decides either way, and we would rather establish the position with a check than declare a house permitted development on sight.
Building regulations apply regardless of the planning route. A converted loft makes a two storey house a three storey one, so Part B fire safety normally requires a protected stairwell running to a final exit, fire doors to habitable rooms off it and interlinked alarms throughout. Part K governs the new stair, which is why a space saver stair is only acceptable where it serves a single room. Terraced houses here also mean party wall notices on both sides once steels bear into shared masonry.
- Ventilation paths kept clear at eaves and ridge
- Protected stair enclosure and fire doors to Part B
- Rooflight conversions where the roof line must not change
- Insulation between and over rafters to Part L
- L-shaped dormers over a rear closet wing
Why Choose GS Renovation in Borough
In Borough the constraint is usually consent and access, not ambition. GS Renovation surveys the ridge height honestly, coordinates the engineer, builds the steelwork and the dormer, and takes Southwark building control through to a completion certificate. You get a dedicated project manager, a fully insured contractor, and 4.9 from 31 MyBuilder reviews behind the work.
- A written scope and programme agreed before work starts
- A dedicated project manager from first survey to handover
- Honest updates if a date or a detail has to move
- Waste cleared as we go, not left piled in the garden
- Protected stair route and fire doors detailed to Part B
- Staircase set out to Part K within the space you have