GS Renovation carries out loft conversions across Greater London, from Victorian terraces and interwar semis to period houses in conservation areas. The right conversion depends on your roof, your house type and your local authority, not on a standard package. We coordinate the structural engineer, build the steelwork and floor, and take the job through building control.
The five loft types and when each applies
A rooflight conversion adds no volume and simply lines and floors the existing roof space, which makes it the cheapest option at an indicative £30,000 to £45,000 for London in 2026. A rear dormer squares off the back slope and creates real standing height, roughly £45,000 to £65,000. An L-shaped dormer wraps over a Victorian closet wing, roughly £55,000 to £80,000, and is the classic terraced house answer across much of inner London.
Hip to gable suits an interwar semi or end terrace whose roof slopes in at the side, usually combined with a rear dormer at roughly £55,000 to £80,000. A mansard is the steepest and most expensive form, roughly £70,000 to £100,000 or more, and adds the most volume. It is common where a conservation area would refuse a dormer. An en suite typically adds around £8,000 to £15,000 to any of them.
Head height, planning and building control
Before design or budget, measure the ridge. Roughly 2.2m to 2.4m from the top of the existing ceiling joists to the underside of the ridge is what allows a conversion without lowering the ceilings below or raising the roof. Loft conversions are often permitted development within volume allowances commonly cited as 40 cubic metres for a terrace and 50 for a semi or detached house, but those rights disappear in conservation areas, on listed buildings and under Article 4 directions.
Building regulations apply even where planning does not, and they are where most of the engineering sits. Part B governs the protected stair route to a final exit, fire doors and interlinked alarms. Part K sets stair rise, going and headroom, which is why a space-saver stair is only acceptable serving a single room. The new floor is carried on engineer-sized joists off steel beams spanning between the party walls onto padstones.
- Building control inspections booked at floor, steel and completion
- New floor joists independent of the existing ceiling
- Ventilation paths kept clear at eaves and ridge
- Velux and conservation rooflights fitted and flashed
- Head height and ridge survey before design
The GS Renovation Difference in London
London homeowners choose GS Renovation because one team carries the whole loft: engineer coordination, steel beams and floor structure, dormer or gable construction, a compliant staircase, the fire strategy and building control sign-off with your local authority. We work cleanly in occupied houses and price honestly from a proper survey. Fully insured, rated 4.9 from 31 MyBuilder reviews, Companies House no. 14611254.
- Dust screens and floor protection in occupied homes
- Party Wall notices prepared for steels bearing into a shared wall
- Water tank removed and the system converted where it blocks the space
- Site left safe and secure at the end of every day
- Neighbours given notice before the noisy stages
- Ridge height measured before any design work is commissioned