House Extensions Uxbridge
Single and double storey extensions in Uxbridge, 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 extensions across Uxbridge, where the 1930s and post-war semis and detached houses often sit on generous plots with room to grow. We handle the foundations, the steelwork, the roof and the full fit-out, so your new space feels part of the house rather than bolted on.
In Uxbridge, 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 Uxbridge: 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 Uxbridge
Uxbridge range: choose above
Rear and side-return extensions in Uxbridge
The wide plots typical of Uxbridge's semis and detached houses, 1930s and post-war alike, lend themselves to rear extensions and to filling the side passage that runs alongside so many semis. The rear extension is the one we are asked about most, usually as a kitchen extension: on a semi, permitted development allows a single storey addition up to 3 metres deep, or up to 6 metres through the prior approval route, which is enough to bring the kitchen into the new space with rooflights or a lantern over the table. Where more width is wanted, a wrap-around scheme combines the rear and the side return for a much larger ground floor. We dig and pour the foundations, build the shell, install the steel where walls come out and tie the new roof neatly into the existing.
Whether your Uxbridge project falls under permitted development or needs a full planning application depends on the property. Many detached and semi-detached homes in UB8 have permitted development rights for a modest rear extension, but corner plots, previous additions and any work to the front usually push it into a planning application to Hillingdon Council. We advise on which route applies before any drawings are finalised.
Housing in Uxbridge
Count the homes in Uxbridge and you get about 12,630: 71% built since 1945, 17% between the wars and 12% before 1919, with flats at 47% and houses at 53%. A rear extension on a semi in Uxbridge digs beside the attached neighbour, so one party wall notice is usual, and 17% of homes here are semi-detached.
Why deeper prior approval extensions stop at 4 metres in Uxbridge
Uxbridge sits under Hillingdon's large rear extensions Article 4 Direction, which has covered every part of the borough since 22 September 2014. Under it, an extension loses permitted development rights once it projects more than 4 metres past the rear wall of the original dwelling. So the deeper single storey extensions that the prior approval route allows in much of England are not available here beyond that depth. If a design reaches further back than 4 metres from the original rear wall, plan for a householder planning application from the start.
In Uxbridge 33% of homes are semi-detached or detached, and those are the houses where a larger scheme is tempting. If the scheme stays within permitted limits, Hillingdon's fast-track service determines householder lawful development certificate applications within 21 days of receiving the fast-track fee, which confirms the position in writing before the foundations are dug. If it goes beyond them, Hillingdon's pre-application Category F covers complex or large scale extension proposals, and taking the design there first shows how an Uxbridge scheme is likely to be viewed before the full cost of drawings is spent.
Double storey extensions on Uxbridge plots
Where the plot allows, a double storey extension adds a larger kitchen or living space below and a bedroom or bathroom above, making far better use of the generous gardens found across much of Uxbridge. We assess the existing foundations, deepen or underpin where the loads demand it, and carry the new upper floor on properly sized steel beams tied back into the original structure of the house.
A two-storey addition almost always needs a planning application to Hillingdon Council rather than relying on permitted development, and where the flank wall sits near the boundary with the adjoining semi, the Party Wall Act comes into play. We coordinate the planning drawings and submission, the building regulations and the full fit-out, and where the Party Wall Act applies you serve the notices as the building owner with the drawings we supply, so decoration, heating and services are all finished by the same team you started with.
Kitchen extensions in Uxbridge
62% of the houses in Uxbridge are semi-detached or detached, which usually leaves room for a kitchen extension across the full rear width, with a steel beam over the opening into the house. The fit-out is priced on its own page, kitchen renovation in Uxbridge; the build figures are in the table above.
- Party wall process explained, and the extension built to the award
- Full fit-out, finishing and making good
- Brickwork and mortar matched to the existing elevation
VOA Council Tax stock of properties, March 2025, for Uxbridge Common & Swakeleys, Uxbridge Central & Brunel and Uxbridge West. Counts rounded by the VOA.
Trusted House Extensions in Uxbridge
Uxbridge homeowners choose GS Renovation because we run the extension end to end, from advising whether it is permitted development or a Hillingdon Council application through to the final coat of paint. One accountable team means the foundations, steel, roof and finishes join up, the party wall process is explained and the work is built to any award, and you are not left chasing separate trades across a UB8 building site.
- Fully insured, with cover in place on every site
- Foundation depth set after trial holes, drains and trees are checked
- Building control inspected at foundation, damp course and steel stages
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
Saiid did a complete refurbishment of our small bathroom. This involved ripping out the existing bath/shower, basin, toilet, pipework, and tiles and…
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 Uxbridge
Are there hidden costs with house extensions in Uxbridge?
Hidden costs on house extensions in Uxbridge come from what the UB8 survey cannot see, not from the quotation, which sits within £2,000 to £2,800 per m² for a rear extension (indicative). Older property can uncover wiring, timber or drainage, and GS Renovation names what it suspects before starting. Approvals are never a surprise extra: building regulations approval from foundations to completion is priced from day one.
Will my Uxbridge extension need planning permission or is it permitted development?
Many Uxbridge semis and detached homes can take a single storey rear extension under permitted development, but double storey additions, corner plots, previous extensions and any work facing the road usually need a planning application to Hillingdon Council. We check your rights and the constraints on your UB8 plot before committing to a design.
How are foundations decided for an Uxbridge extension?
From the ground on your plot, not a standard depth. Towards the Colne valley the soil can vary within a street, and trees nearby affect it too. Trial holes show what is there, the engineer sets the depth, and building control inspects the open trench before any concrete. Deeper or wider footings are designed only where the evidence calls for them.
How is a wrap-around extension on an Uxbridge semi supported at the corner?
Usually with a steel post or frame. Once both the rear wall and the side wall are opened, the corner of the house above has nothing to stand on, so the engineer designs beams meeting on a post, with its own foundation beneath. Building control inspects the steel and bearings. The frame goes in after the extension is weathertight and before the walls are opened.
Will my Uxbridge extension need changes to the heating?
Usually. A bigger room with more glass asks more of the boiler, and it must have the spare output to cope. Part L insulation standards for the new walls, floor and roof reduce that demand. We calculate the extra heat load, choose radiators or underfloor loops, and any gas alteration goes to a Gas Safe registered engineer. Settle it before the slab is poured, since pipes may run in it.
Does a two-storey extension beside the adjoining Uxbridge semi need a party wall notice?
Often. If the new foundations lie within 3 metres of the neighbouring house and go deeper than its footings, the Party Wall etc. Act 1996 requires one month's notice. On a semi the neighbour is often that close. They can consent or dissent, and a dissent leads to an award before digging starts.
What does an extension application need for a house in The Greenway, Uxbridge?
A heritage statement, as well as the drawings. The Greenway, Uxbridge was designated a conservation area on 16 October 1975, and Hillingdon says planning applications for development in conservation areas should be supported by a heritage statement. It explains how the extension's size, materials and roof relate to the houses around it. Write it with the designer while the scheme is still flexible, rather than after the drawings are fixed.
When would the Community Infrastructure Levy apply to an Uxbridge extension?
When the scheme crosses the threshold. Hillingdon's CIL covers every proposal that adds 100m2 of new floorspace or an extra dwelling. A self-contained annex or a very large wrap-around is where that question arises. Hillingdon adopted its CIL Charging Schedule on 10 July 2014. Ask the planning agent to confirm in writing whether your scheme is chargeable and whether any relief must be claimed, and do it before work starts, not after.
Why does the floor area band matter for an Uxbridge extension's building control charge?
Because Hillingdon charges by size. One charge covers a domestic extension of less than 40m2, whether on full plans or a building notice, and a higher charge covers a domestic extension of 40m2 to 60m2. An Uxbridge scheme that grows during design can move from one band to the next. Ask the designer to state the measured area on the drawings, so the application and the charge match the extension as built.
Every Service, One Team
More GS Renovation Services in Uxbridge
One team for every GS Renovation service in Uxbridge:
Same Service, Nearby Areas
House Extensions Near Uxbridge
We carry out house extensions across Uxbridge and the surrounding areas. Explore a nearby location:
Ready to Start Your Uxbridge Project?
Free, no-obligation quote for house extensions in Uxbridge.