Loft conversions in Uxbridge: is it the right way to add space?
R.A Developments builds loft and dormer conversions for Uxbridge homeowners. We will tell you honestly whether a loft conversion or an extension gives you more for your money, then quote it in writing at a fixed price.
Loft conversion or house extension: which should you choose?
Both add space; they suit different homes and budgets.
| Loft conversion | House extension | |
|---|---|---|
| Where the space goes | Into the roof: bedroom, office, bathroom | Onto the ground floor or first floor: kitchen, living space, extra bedroom |
| Garden | Usually untouched | Uses part of your garden |
| Typical build cost (published 2026 guides) | Dormer around £40,000 to £45,000 nationally, London typically 10 to 15 per cent higher, so roughly £44,000 to £52,000 | Single-storey around £3,000 to £5,000 per m² in London, so a 30 m² extension is roughly £90,000 to £150,000 before VAT and fees |
| Typical on-site time | Around 6 to 8 weeks for a dormer | Longer, depending on size and structure |
| Best for | Adding bedrooms and a bathroom without touching the garden | Improving kitchen and living space and how the ground floor works |
These are illustrations from published guides, not R.A Developments prices. The right answer depends on your property, and we will talk it through on a free site visit.
Source note: Loft Plans (2026 UK guide); Architecture for London (2026 London extension guide).
Planning and permitted development in Hillingdon
Many loft conversions can be built under permitted development, without a 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 above the existing ridge line, similar materials and obscure-glazed side windows.
You will need planning permission if your home is a flat, listed, in a conservation area, subject to an Article 4 direction or if you want a front-facing dormer. Hillingdon has 31 designated conservation areas, so check your address with Hillingdon Council early. We check the position for you before we quote.
What a loft conversion involves
- A survey of your roof structure, head height and possible stair position.
- Structural design: steel beams and floor strengthening are typical.
- Building regulations: structure, fire safety and escape, stairs, insulation and ventilation must all comply.
- Party wall notices if you share a wall with a neighbour; the Party Wall etc. Act 1996 sets notice periods of at least one to two months.
- The build: guides suggest around 4 to 10 weeks on site for most conversions and 4 to 6 months overall including design and approvals.
We coordinate the engineer, building control and approvals as part of the job.
How we run your loft conversion
- 1Free consultation and site visit.
- 2Written fixed-price quote.
- 3Drawings, structural design and approvals.
- 4The build, with one dedicated project manager and weekly progress updates.
- 5Handover. Snagging walk-through and completion paperwork.
Also explore loft conversions in West London, house extensions in Uxbridge, and home renovations in West London.
Loft conversion FAQs (Uxbridge)
See what your loft could become
Book a free site visit. We will check your roof and head height and send you a written fixed-price quote, with no obligation.