Loft conversions in West London: more space without the cost of moving
R.A Developments builds loft and dormer conversions for homeowners across West London. Get honest advice on what your roof can take, a written fixed-price quote, and one project manager from start to finish.
Is a loft conversion right for your home?
A loft conversion can add a bedroom, a home office or a bathroom suite without using up your garden. The right design depends on your roof structure, head height, and where a staircase can go. We assess all three at a free site visit and tell you honestly what is practical and what is not.
The main types of loft conversion
Loft conversions are usually described by how much they change the roof. Published 2026 guides give these typical national build costs, with London commonly around 10 to 15 per cent higher:
| Type | What it is | Typical build cost (UK guide) | Typical on-site time |
|---|---|---|---|
| Rooflight (Velux) | Roof windows added to the existing roof shape | £25,000 to £30,000 | 4 to 6 weeks |
| Dormer | A box extension to the roof slope that adds headroom and floor space | £40,000 to £45,000 | 6 to 8 weeks |
| L-shaped dormer | A dormer that wraps across two roof slopes | £45,000 to £55,000 | 8 to 10 weeks |
| Hip-to-gable | Replaces a sloping side roof with a vertical wall | £45,000 to £55,000 | 8 to 10 weeks |
| Mansard | A steep, near-vertical roof slope, often needing planning permission | £75,000 to £100,000+ | 12 to 16 weeks |
These are guide figures, not R.A Developments prices. We offer loft and dormer conversions; tell us what you are considering and we will recommend the right approach for your roof.
Source note: Loft Plans, "Loft Conversion Costs, Planning & Build Stages, 2026 UK Guide".
Planning permission or permitted development?
Many loft conversions can be done under permitted development, with no full planning application. The usual volume limits are 40 cubic metres for terraced houses and 50 cubic metres for semi-detached and detached houses. Conditions include no extension beyond the front roof slope, no dormer higher than the existing ridge, materials similar to the existing roof, and obscure-glazed side windows.
Full planning permission is needed for flats, listed buildings, conservation areas, homes with Article 4 directions, and front-facing dormers. A Lawful Development Certificate is a sensible way to record that your loft conversion was lawful when you come to sell. Confirm the position for your own home with your local council.
Source note: Loft Plans (2026 guide); Planning Portal.
Building regulations and party walls
Every loft conversion must meet building regulations, covering structure, fire safety and escape, stairs, insulation and ventilation. If you share a wall with a neighbour, the Party Wall etc. Act 1996 may also apply, and notice periods start at one to two months. We coordinate structural engineers and building control as part of the job.
How your loft conversion project runs
- 1Free consultation and site visit, including head height and roof structure.
- 2Written fixed-price quote, itemised.
- 3Drawings, structural design, approvals and any party wall notices.
- 4The build, with one project manager and weekly progress updates.
- 5Handover. Snagging walk-through and completion paperwork.
Guide timeline: published guides suggest around 4 to 6 months from first survey to finished loft, including design, approvals and roughly 4 to 10 weeks on site for most conversions.
Also explore loft conversions in Uxbridge, house extensions in Uxbridge, and home renovations in West London.
Loft conversion FAQs (West London)
Find out if your loft can be converted
Book a free site visit. We will check head height and roof structure, talk through your options and send a written fixed-price quote, with no obligation.