GSM Builders Ltd builds loft conversions in Hayes – UB3 and UB4, including Hayes Town, Hayes End, Harlington, Yeading, Wood End and Botwell. Our yard is on Leven Way, so a Hayes loft is a home game for us: we can survey within days, the scaffold and skip lorries know the roads, and the site manager is never more than ten minutes away.
Hayes roofs and the loft that suits them
Most of Hayes was built between 1925 and 1939 – the semis around Coldharbour Lane, Hayes End and Yeading, and the terraces off the Uxbridge Road and Station Road. These houses have hipped roofs, which leave a cramped triangle inside. The conversion that works here, and the one we build most often, is a hip-to-gable with a rear dormer: the sloping side of the roof is built up into a full gable wall and a flat-roofed dormer is added across the back, creating a bedroom of 20–30 m² with room for an en-suite. Ridge heights on these houses are usually generous, so head height is rarely a problem.
Terraces in Hayes Town and Botwell take a rear dormer alone. Newer houses around Hayes Village and the former Nestlé site often have trussed roofs, which need the trusses replacing with steel and timber before the space can be used – we do this regularly, and it is priced into the quote.
Loft conversion cost in Hayes (2026)
| Loft type | Suits | Indicative cost (ex VAT) | On site |
|---|---|---|---|
| Velux / rooflight | Roofs with 2.3 m+ head height | £35,000 – £48,000 | 4–6 weeks |
| Rear dormer | Terraces, semis | £48,000 – £70,000 | 6–8 weeks |
| Hip-to-gable + rear dormer | 1930s semis and detached | £58,000 – £85,000 | 8–10 weeks |
| L-shaped dormer | Victorian/Edwardian terraces with outrigger | £65,000 – £88,000 | 8–10 weeks |
Prices include structural work, staircase, insulation, windows, electrics, plumbing for an en-suite, plastering and decoration. An en-suite is typically £6,000–£12,000 of the total. See the full West London loft cost guide.
Planning permission for lofts in Hayes
Almost all Hayes lofts are permitted development: up to 40 m³ of extra roof space on a terrace and 50 m³ on a semi or detached house, with the dormer at the rear and below the ridge line. Front-facing dormers need planning. The local exceptions are homes in the Harmondsworth and Harlington conservation areas, flats, and houses on estates with restrictive conditions – we check your address before quoting. We recommend a Lawful Development Certificate from Hillingdon Council (£129) for every loft so you have proof when you sell. Building Regulations approval is required on every loft, and because Hayes is almost entirely semis and terraces, the Party Wall Act applies to the steel beams.
Homes south of the A4 in Harlington sit under the Heathrow approach – we specify acoustic glazing and upgraded roof insulation there so the new bedroom is quiet.
How the project runs
- Free survey – we measure head height, check the structure and staircase options and give you a written, itemised quote.
- Drawings and calculations – Building Regulations drawings and structural engineer’s calculations; Lawful Development Certificate or planning application to Hillingdon Council if needed.
- Party Wall – notices served to neighbours where steel beams bear on a shared wall.
- Build – scaffold, steels, floor, dormer, roof, windows, staircase, first fix, insulation, plaster, second fix, bathroom, decoration. Most lofts are built from the outside first, so you stay at home.
- Sign-off – Building Control completion certificate, snagging and a 12-month workmanship warranty.
Why choose GSM Builders Ltd for a loft in Hayes?
- Based at Leven Way, Hayes UB3 – genuinely local, on site within minutes
- One team from drawings to completion certificate; no separate architect, engineer and builder to coordinate
- Written itemised price with agreed payment stages
- Fully insured; Building Control certified on every loft; 12-month warranty
- We know Hillingdon Council’s planning and Building Control teams and the borough’s conservation areas
Nearby
Loft conversions Uxbridge · Loft conversions Hillingdon · Builders in Hayes · House extensions Hillingdon · All loft conversion services
Hayes loft conversion FAQs
How much does a loft conversion cost in Hayes?
A rear dormer loft in Hayes typically costs £48,000–£70,000 and a hip-to-gable with rear dormer £58,000–£85,000, excluding VAT, including structure, stairs, insulation, windows, electrics, plumbing, plastering and decoration. GSM Builders Ltd provides free surveys and itemised quotes.
Do I need planning permission for a loft conversion in Hayes?
Usually not. Lofts up to 50 m³ on a semi (40 m³ on a terrace) with a rear dormer are permitted development. Exceptions are front dormers, flats, and homes in the Harmondsworth or Harlington conservation areas. We recommend a Lawful Development Certificate from Hillingdon Council.
How long does a loft conversion take in Hayes?
Six to eight weeks on site for a rear dormer, eight to ten for a hip-to-gable, after two to four weeks of drawings and approvals. You can live at home throughout.
Can a 1930s semi in Hayes have a loft conversion?
Yes – they are ideal. The hipped roof is converted to a gable and a rear dormer added, typically creating a 25–30 m² bedroom with en-suite.
Get a free loft survey in Hayes
Send us your address and a photo of the back of the house. We will visit, measure the head height and give you a written quote without obligation.