Azar Construction Ltd · London builders
Loft conversions in London
Dormer, hip-to-gable and mansard conversions that create proper habitable rooms, with staircases, fire separation and insulation signed off by building control.
Loft conversion types
- Rooflight conversions, the least invasive option, where the existing roof shape stays and windows are fitted into the slope.
- Rear dormer conversions, which add vertical walls and a flat roof to gain floor area and headroom.
- Hip-to-gable conversions, which replace a sloping side with a vertical gable wall, common on semi-detached and end-of-terrace houses.
- Mansard conversions, which rebuild the roof with a steep, near-vertical slope to give almost a full extra storey.
Is your loft suitable?
A common rule of thumb is around 2.2 metres from the top of the ceiling joists to the underside of the ridge, but a survey is the only way to know. Roof structure, chimney breasts, water tanks and the position of the new staircase all affect what is possible.
Planning permission and permitted development
Many loft conversions can be built without planning permission under permitted development, provided the added roof space stays within the volume allowances: 40 cubic metres for a terraced house and 50 cubic metres for a semi-detached or detached house. The extension must not rise above the highest part of the existing roof, and side-facing windows must be obscure-glazed.
Flats and maisonettes have no permitted development rights, and conservation areas and Article 4 areas are restricted. A mansard often needs planning permission. Always confirm with your local authority.
Building regulations: what makes it a legal bedroom
A loft conversion needs Building Regulations approval. Without it, the room is not a lawful bedroom and can cause problems when you sell or remortgage. Typical requirements include:
- Floor strengthening and structural steelwork designed by an engineer.
- A fixed staircase with adequate headroom, not a loft ladder.
- A protected escape route with fire doors, plus mains-linked smoke alarms.
- Insulation, ventilation and sound separation between floors.
If steelwork bears on a party wall, the Party Wall etc. Act 1996 may require notice to your neighbours. We coordinate the structural engineer, party wall surveyor and building control inspector.
Common questions
Often not, if the work falls within permitted development volume limits. Flats, conservation areas, Article 4 areas and most mansard conversions need a closer look, so check with your local authority before you start.
A site survey is needed. As a guide, around 2.2 metres of height from the top of the ceiling joists to the ridge makes a conversion straightforward, but roof structure and stair position also matter.
It shows the conversion meets fire safety, structural and insulation standards. Buyers, solicitors and lenders commonly ask for the completion certificate when you sell.
Usually, yes. The work is mostly above you, and the stairwell is the main point of disruption. We agree working hours and protect the areas you live in.
Related services
We work across Greater London and, by arrangement, the Home Counties. See areas we cover or read our verified reviews on Checkatrade.
This page is general information, not structural, planning or legal advice. Rules depend on your property and local authority. See our disclaimer.