GSM Builders Ltd provides experienced builders in Hounslow and the surrounding TW postcodes. Hounslow Central and West, Heston, Cranford, Hounslow Heath, Isleworth and Feltham. We are based in Hayes, around 15 minutes north, and have been extending, converting and refurbishing homes in the borough for years.
Hounslow homes: 1930s semis, terraces and post-war houses
Hounslow grew rapidly between the wars, so a huge share of its housing is 1930s semi-detached and terraced homes with hipped roofs, bay windows, side passages and generous rear gardens. That combination makes them ideal candidates for three of the projects we do most: single-storey rear extensions for an open-plan kitchen-diner, hip-to-gable loft conversions with a rear dormer (the hipped roof is converted into a gable to create a full-size bedroom and bathroom upstairs), and garage conversions where an unused side garage becomes a home office, playroom or downstairs bedroom.
Hounslow also has a large number of 1960s, 80s houses and flats in Heston and Cranford, and Victorian terraces in Isleworth and around Hounslow High Street. We work on all of them.
Planning permission and Heathrow considerations
Planning applications are handled by the London Borough of Hounslow. Most single-storey rear extensions up to 3 m (or 6 m with prior approval) and most loft conversions on semis fall under permitted development, but flats, maisonettes and homes in conservation areas such as Isleworth Riverside, Spring Grove and Hounslow Heath need an application. We deal with all of this for you.
One thing that is specific to Hounslow: large parts of the borough sit under the Heathrow flight paths. When we build an extension or convert a loft here we routinely specify acoustic-rated glazing, upgraded roof and wall insulation and careful detailing of trickle vents so the new space is quiet as well as warm. If you are eligible for Heathrow’s noise insulation schemes, we can install to the required standard.
Building services we offer in Hounslow
- House extensions, single-storey rear, side-return, wrap-around and double-storey
- Loft conversions. Velux, rear dormer, hip-to-gable and L-shaped
- Full property refurbishment and renovations
- Kitchen fitting and kitchen renovation
- Bathroom renovation and wall tiling
- Roofing, plastering, flooring and painting & decorating
- 24/7 emergency call-outs, plumbing, electrics, glazing and boarding-up
Why choose GSM Builders Ltd in Hounslow?
- Genuinely local. Our base at Leven Way, Hayes UB3 is about 15 minutes by road from Hounslow, so site visits, quotes and snagging calls are quick and easy.
- One team from start to finish. Design input, structural calculations, Building Control liaison, all trades and decoration under one contract.
- Building Control approved work. Every structural project is signed off with completion certificates you will need when you sell or remortgage.
- Clear written quotes. Itemised pricing, agreed payment stages and no hidden extras.
- Fully insured with public liability cover and a 12-month workmanship warranty.
Recent types of work in Hounslow
- 4 m rear kitchen extension on a 1930s semi in Hounslow West with roof lantern and underfloor heating
- Hip-to-gable and rear dormer loft conversion in Heston creating a master suite
- Garage conversion to a ground-floor bedroom and wet room in Cranford
- Complete renovation of a two-bedroom Victorian terrace in Isleworth
What building work costs in Hounslow (2026)
These are the 2026 ranges we quote for Hounslow (TW3, TW4, TW5 and TW7), excluding VAT. They assume a standard specification and reasonable access; the cost calculator gives a figure for your own project, and a free site survey gives you a fixed written price.
| Project | 2026 price (excl. VAT) | Time on site |
|---|---|---|
| Single-storey rear extension (3 m) | £48,000 to £68,000 | 8 to 10 weeks |
| Side-return extension | £45,000 to £65,000 | 8 to 10 weeks |
| Wrap-around extension | £65,000 to £95,000 | 10 to 14 weeks |
| Rear dormer loft conversion | £38,000 to £48,000 | 6 to 8 weeks |
| Hip-to-gable loft with en-suite | £55,000 to £85,000 | 8 to 10 weeks |
| Whole-house refurbishment (3-bed) | £70,000 to £150,000 | 10 to 18 weeks |
| Kitchen fitting (supply & fit) | £12,000 to £30,000 | 2 to 4 weeks |
| Bathroom refit | £8,000 to £20,000 | 2 to 3 weeks |
Drawings, structural calculations and Building Control fees add £2,500 to £4,500. Where planning is needed, Hounslow Council charges £548 for a householder application or £249 for prior approval (fees from 1 April 2026). Our planning guide explains which route applies, and the loft conversion comparison covers which loft type suits your roof.
Frequently asked questions
Do I need planning permission for an extension in Hounslow?
Most single-storey rear extensions up to 3 m on a semi or terrace (4 m detached) are permitted development, with 3 to 6 m possible under prior approval. Conservation areas such as Osterley Park and parts of Isleworth and Chiswick remove those rights, so check your address before assuming.
Does being under the Heathrow flight path affect building work in Hounslow?
It does not change planning, but it changes specification. Acoustic glazing, upgraded roof and dormer insulation and ventilation that works with windows closed are all worth specifying on a loft or extension in Hounslow, and they make the finished room far more usable.
How quickly can you get to Hounslow?
Our yard is on Leven Way in Hayes, about 15 minutes from Hounslow, so site visits, deliveries and snagging calls are straightforward. There is no London-wide travel premium in our pricing.
Do you handle Building Control in Hounslow?
Yes. Every extension, loft conversion and structural alteration needs Building Regulations approval and a completion certificate regardless of planning. We make the application, book the inspections and hand you the certificate at the end, you will need it when you sell.
Are you insured and do you give a warranty?
Yes, public and employer’s liability insurance, an itemised written quote before anything starts, staged payments against completed work and a 12-month workmanship warranty in writing on every contract.
Nearby areas we also cover
Hayes · Southall · Harmondsworth · Sipson · West London
Free quotes for building work in Hounslow
Call us or send a message with your address and a few photos, and we will book a free site visit and provide a detailed written quote.