GSM Builders Ltd builds house extensions across Hounslow – Hounslow Central and West, Heston, Cranford, Hounslow Heath, Isleworth, Feltham and Hanworth. We are based in Hayes, 15 minutes north, and the borough’s 1930s semis are exactly the houses our rear and wrap-around extensions are designed for.
Want a number first? Use our free extension cost calculator for an instant 2026 range, then book a free survey for a fixed price.
Hounslow houses and the extensions that suit them
Hounslow grew fastest between the wars, so most of the borough is semi-detached and terraced housing with side passages and long gardens. That makes three projects straightforward: a 3–6 m single-storey rear extension for an open-plan kitchen-diner; a wrap-around that uses the side passage for a utility room and downstairs WC; and a double-storey rear extension adding a bedroom above. The 1960s–80s houses in Heston and Cranford often have a garage that converts cheaply, and the Victorian terraces of Isleworth and Hounslow High Street take side-return extensions.
Extension costs in Hounslow (2026)
| Extension | Typical size | Indicative cost (ex VAT) | Build time |
|---|---|---|---|
| Single-storey rear, 3 m | 18–22 m² | £50,000 – £70,000 | 8–10 weeks |
| Single-storey rear, 6 m (prior approval) | 30–36 m² | £75,000 – £110,000 | 10–12 weeks |
| Side-return | 8–12 m² | £40,000 – £60,000 | 8–10 weeks |
| Wrap-around | 30–40 m² | £85,000 – £130,000 | 12–14 weeks |
| Double-storey rear | 40–50 m² | £110,000 – £160,000 | 14–18 weeks |
Hounslow prices match Hillingdon. The detail is in our West London extension cost guide.
Planning permission in Hounslow
The London Borough of Hounslow handles planning. Single-storey rear extensions up to 3 m are permitted development and the council actively encourages the larger home extension prior-approval route for 4–6 m extensions (£120, 42 days, neighbour consultation). Double-storey and wrap-around extensions normally need a householder application (£258, eight weeks). Conservation areas include Isleworth Riverside, Spring Grove, Hounslow Heath and the Bedford Park border, and flats and maisonettes always need permission. We check, draw, submit and manage all of it.
Building under the Heathrow flight path
A large part of Hounslow sits under the Heathrow approach. On every extension here we specify acoustic-rated glazing, upgraded roof and wall insulation and acoustic trickle vents, so the new room is as quiet as the rest of the house. Where a property qualifies for Heathrow’s noise insulation schemes, we install to the required standard. Ground conditions are mostly London clay and Thames gravels; our engineer designs foundations to suit, and Building Control inspects at each stage.
How we run an extension
- Free site visit and itemised quote
- Drawings and structural calculations for planning and Building Regulations
- Planning or prior approval submitted to Hounslow Council and managed by us; Lawful Development Certificate where permitted development applies
- Party Wall notices served and surveyors coordinated
- Build with a dedicated site manager – foundations, drainage, steel, walls, roof, glazing, first fix, plaster, second fix, decoration
- Building Control completion certificate, snagging and a 12-month workmanship warranty
Why GSM Builders Ltd for an extension in Hounslow
- Family-run building company based at Leven Way, Hayes – 15 minutes from Hounslow
- One contract from drawings to completion certificate
- Written, itemised price with agreed payment stages
- Fully insured, Building Control certified, 12-month warranty
- Experienced with Hounslow’s housing stock and its council’s planning rules
Nearby
Builders in Hounslow · Builders in Hayes · Builders in Southall · Extensions in Ealing · All extension services
Hounslow extension FAQs
How much does a house extension cost in Hounslow?
A 3 m single-storey rear extension in Hounslow typically costs £50,000–£70,000 excluding VAT and kitchen; a 6 m extension £75,000–£110,000; a double-storey extension £110,000–£160,000. GSM Builders Ltd provides free itemised quotes.
Do I need planning permission for a rear extension in Hounslow?
Not for a 3 m rear extension on a house, and 4–6 m extensions can use Hounslow Council’s prior-approval route rather than a full application. Double-storey, wrap-around, flats and conservation-area homes need a householder application.
Do you allow for Heathrow aircraft noise?
Yes. Acoustic glazing, upgraded insulation and acoustic vents are specified as standard on extensions under the flight path in Hounslow, Cranford and Heston.
Which areas of Hounslow do you cover?
Hounslow Central and West, Heston, Cranford, Hounslow Heath, Isleworth, Osterley, Feltham and Hanworth, from our base in Hayes.
Start your Hounslow extension
Tell us your address and what you would like to build and we will arrange a free site visit.