House Extensions Hounslow
Single storey rear and double storey extensions in Hounslow, planning, structure and build under one contract.
- Rated 4.9 from 31 reviews on MyBuilder
- Single-storey rear extension from £40,000
- Free site survey, itemised quote
GS Renovation builds house extensions throughout Hounslow, where half the homes are flats and the houses range from Victorian terraces near the town centre to the interwar semis of Heston and Hounslow West. We handle everything from foundations to final fit-out, including single storey kitchen extensions across the back of a semi.
In Hounslow, a single-storey rear extension typically starts from £40,000, or £2,000 to £2,800 per m² (indicative London ranges, Architecture for London, Resi, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Hounslow: the structural engineer we appoint designs the structure, we build it, and building control signs it off.
Price guide
| Work | Indicative London range |
|---|---|
| Single-storey rear extension | from £40,000 |
| Rear extension, per m² | £2,000 to £2,800 |
| Side return, per m² | £2,400 to £3,200 |
| Wraparound, per m² | £2,400 to £3,200 |
| Double storey, per m² | £1,800 to £2,600 |
| Basement extension | see the basement page |
Indicative London ranges (Architecture for London, Resi, MyBuilder and Checkatrade, 2026), not a quotation. Prices checked September 2026. Full breakdown: Extension Costs & Planning.
Quick estimate for Hounslow
Hounslow range: choose above
Kitchen, side-return and rear extensions in Hounslow
On an interwar semi in Hounslow, a popular choice is a single storey kitchen extension across the back, turning a small kitchen and dining room into one kitchen-diner; on a Victorian terrace, it fills in the side return beside the rear closet wing. We dig and pour the foundations to a depth building control agrees, allowing for nearby trees and for the ground found in the trial holes, which across much of the borough is river terrace gravel over London Clay, then build up in matching brick and tie the new roof into the existing structure.
Wrap-around extensions combine the side return with a rear projection to create a generous kitchen-diner, usually needing a steel beam where the original rear wall comes out. We manage the groundworks, the steel, the roof and the glazing as one job, and because the wall to your neighbour is a shared party wall, you serve the necessary party wall notices before we break ground.
Housing in Hounslow
Of the 111,270 homes the valuation list records in Hounslow, 16% were built before 1919, 28% between the wars and 55% since 1945; 50% are flats and 50% are houses. A rear extension on a terrace in Hounslow digs foundations close to both neighbours, so notices to both are normal, and 26% of homes here are terraced.
Hounslow rear extension depths and the 2024 design codes
Hounslow's residential extension guidelines set a maximum single storey rear extension depth of 3.05m for terraced houses and 3.65m for semi-detached houses, with a larger figure for detached houses. Each house type has its own limit, so test the drawing against the right one first. Where the extension needs planning permission, a semi drawn to the detached figure, or a terrace drawn to the semi figure, starts the application from the wrong place. Ask the designer to show on the plan where the depth is measured from, so the officer and you are reading the same number.
Check which document the figure comes from before relying on it. Hounslow Council adopted the Character, Sustainability and Design Codes Supplementary Planning Document as of 14 May 2024, and it supersedes the Residential Extensions Guidelines SPD (2017). A neighbour's extension approved under the 2017 guidance is not a safe precedent on its own, so ask for the current code to be checked for your street before the depth is fixed. Where the answer is unclear, paid pre-application advice is a cheaper place to find out than a refusal.
Planning and permitted development in Hounslow
Whether your extension is permitted development or needs a full planning application depends on the property and its size. Many single-storey rear extensions on Hounslow's terraces fall under permitted development rights, but homes in a conservation area, such as around Osterley Park, or any property that has already been extended, often need permission from Hounslow Council. We advise honestly on which route applies before you commit.
Either way, the structural build is governed by building regulations, so building control inspects the foundations, the steelwork, the insulation and the drainage as the work proceeds. Your architect or designer prepares the drawings for a planning application or a lawful development certificate; we can recommend one and coordinate it, and we programme the build around the party wall notices you serve, so your Hounslow extension is compliant from footings to finish.
Double storey extensions in Hounslow
Under permitted development a two-storey rear extension can go no more than 3 metres beyond the original rear wall and must stay at least 7 metres from the rear boundary, and in a conservation area it is not permitted development at all. Many gardens are too short for the 7 metre rule, so a double storey extension in Hounslow often needs planning permission from Hounslow Council. On the 26% of homes that are terraced, the neighbours' windows usually decide the depth. Hounslow Council states that there are currently 29 conservation areas in the borough (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- Single and double storey extensions
- Side-return and rear extensions
- Party wall process explained, and the extension built to the award
VOA Council Tax stock of properties, March 2025, for all 29 statistical areas in Hounslow. Counts rounded by the VOA.
Why Hounslow Homeowners Choose GS Renovation
Hounslow homeowners choose GS Renovation because one team carries the extension from foundations to fit-out, including the steel, the roof and the fine finishes. We know the borough's terraces and semis, its mixed ground conditions and the local planning picture, and we keep sites tidy and neighbours informed. Our founder's 30+ years of extensions back the work.
- Rated 4.9 from 31 reviews on MyBuilder
- Brick and mortar matched to the existing elevation
- Insulation and thermal detailing to current regulations
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
The kitchen has been fitted to the high standard. Saaid was polite, professional, tidy, he pays attention to a little details that make huge…
FAQ
Frequently Asked Questions about House Extensions Hounslow
How much should house extensions in Hounslow cost?
Expect house extensions at a Hounslow address to cost £2,000 to £2,800 per m² for a rear extension (indicative), with the property rather than the postcode deciding the figure. At the TW3 survey GS Renovation confirms the detail that matters most, because the drainage run under the footprint decides the foundations. Labour, materials and the Hounslow Council building control fee are then itemised, so another Hounslow quotation can be compared line by line.
Will my Hounslow rear extension need planning permission or is it permitted development?
It depends on the size and the property. Many single-storey rear extensions on Hounslow terraces are permitted development, but if you are in a conservation area or the home has been extended before, you will likely need permission from Hounslow Council. We assess your specific property first. Regardless of the planning route, the build itself needs building regulations approval.
How deep do extension foundations have to go in Hounslow?
Deeper than many owners expect where trees are close and the ground is clay. Much of the borough sits on river terrace gravels over London Clay; where clay is near the surface, roots draw moisture out and the ground shrinks and swells, so the depth is set by the species, height and distance of nearby trees, and building control agrees it. Near a large tree, a reinforced or piled foundation may replace a simple trench.
Can we stay in our Hounslow house while an extension is built?
Usually, because the original rear wall stays up until the extension is roofed and weathertight. Only then is the opening formed with steel, and that is the stage when the kitchen is out of use and dust gets into the house. Planning a temporary kitchen in another room for that stage makes staying in far easier than moving out.
What building control visits happen on a Hounslow extension?
Building control usually inspects the excavated foundations before concrete, the drainage before it is backfilled, the damp-proofing and floor before the slab, the steel over the new opening and the insulation before it is covered, then issues completion. Each visit is booked as that stage is reached, so the programme pauses briefly at each one. Missing an inspection can mean digging or opening up to show the work.
Will a side-return extension make the middle room of a Hounslow terrace dark?
It can, because the side return was the middle room's only source of daylight. The usual fix is glazing the roof over the infill, either a run of rooflights or a fully glazed strip along the boundary wall, so light still falls into the centre of the house. The more glass in that roof, the harder the Part L balance, so glazing is agreed with the insulation design.
Why can a drain near a Hounslow extension decide the building control route?
Because Hounslow requires a full plans application, not a building notice, where an extension is to be built over or within 3m of a public drain or sewer. A rear garden can carry a shared run serving several houses, so find out before the application goes in. The water company's sewer map shows whether a run is public, and a camera survey shows where it really goes. If it is, the application route changes, and the foundations and programme may change with it.
Can the flat roof of a new Hounslow extension be used as a terrace?
Plan on the answer being no. Hounslow's residential extension guidelines say schemes that use the flat roof of a single storey rear extension as a balcony or roof terrace will normally be refused. If you want outdoor space upstairs, raise it with the planners at the start rather than adding a door and railings to a drawing later. Design the roof as a roof, with falls, drainage, insulation and any rooflights, and access only for maintenance.
Does building control cost more for a small Hounslow extension on full plans?
No. Hounslow's Table B charge for a domestic extension of under 40 square metres is the same for a full plans or a building notice application. So the fee is not a reason to pick the quicker route. Choose on risk instead: full plans gets the design checked before foundations are dug, which matters where trial holes, drains or steel could change the build. The charges include VAT, and forming a basement adds a further charge.
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