House Extensions Hillingdon
Single storey rear and double storey extensions in Hillingdon, 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 plans and builds extensions across Hillingdon, adding space to the borough's interwar semis and post-war family houses on their generous plots. We handle everything from single storey kitchen extensions in Ruislip to side-return, double storey and wrap-around additions around Uxbridge and Hayes.
In Hillingdon, 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 Hillingdon: 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 Hillingdon
Hillingdon range: choose above
Kitchen extensions and side additions in Hillingdon
A single storey kitchen extension across the back of a semi is a popular Hillingdon project, turning a small original kitchen and dining room into one kitchen-diner that opens onto the garden. Hillingdon's semis were built on wider plots than inner London terraces, which often leaves room down the side as well, so a side addition or wrap-around can square off the ground floor. The old rear wall comes out on a steel beam the engineer sizes, and the sink, cooker and extraction are planned with the extension rather than after it. We handle the groundworks and foundations, the steel, the roof and the full fit-out.
Every extension starts underground. We dig and pour foundations to suit the ground conditions and any nearby trees or drains, a real consideration on the generous, planted plots common in Ruislip and Ickenham. From there we build the walls, tie in new steel, form the roof and weatherproof, then fit out inside so the new space flows naturally from the original house rather than feeling bolted on.
Housing in Hillingdon
The stock in Hillingdon runs to roughly 118,240 dwellings, 34% of them flats and 66% houses, built 4% before 1919, 37% between 1919 and 1939 and 59% after 1945. A rear extension on a semi in Hillingdon digs beside the attached neighbour, so one party wall notice is usual, and 27% of homes here are semi-detached.
The 4 metre line every Hillingdon rear extension is measured against
Hillingdon's large rear extensions Article 4 Direction applies to the whole borough and came into force on 22 September 2014. It takes away permitted development rights for any residential extension projecting more than 4 metres past the rear wall of the original dwelling. The prior approval route that allows deeper single storey extensions elsewhere in England therefore does not carry a Hillingdon extension beyond that line. Anything deeper needs a planning application, so fix the depth with the designer before the first drawing, and measure it from the original house, not from a later conservatory or kitchen addition.
If your scheme stays inside the permitted limits, get that confirmed before building. Hillingdon's fast-track service determines householder lawful development certificate applications within 21 days of receiving the fast-track fee, and the certificate is something to hand a buyer's solicitor later. If the scheme goes beyond those limits, Hillingdon's pre-application Category F covers small scale minor proposals including complex or large scale extension proposals. It is worth using when a wrap-around or two-storey design sits close to a neighbour's windows. The certificate settles the position in writing; pre-application advice tests a design before it is submitted. Either way, the planning question is answered before any foundation is dug.
Planning and permitted development in Hillingdon
Many single storey rear extensions on Hillingdon semis fall under permitted development, meaning no full planning application, though larger ones may need prior approval and all must still meet building regulations. Larger, double storey or wrap-around projects, and anything to the front, or to the side in a conservation area near Uxbridge, usually need planning permission from Hillingdon Council. We advise which route your property falls under before any drawings are finalised.
Whichever route applies, building regulations always cover the structure, insulation, drainage and fire safety, and building control inspects the work in stages. On semi-detached and terraced homes the Party Wall Act often applies too, where foundations sit near the boundary or a new wall ties into the shared party wall. We coordinate the planning drawings with your designer and the building control application together, so your Hayes or Uxbridge project moves smoothly from drawings to completion.
Side return extensions in Hillingdon
Side returns belong to Victorian and Edwardian terraces, and only 4% of homes in Hillingdon predate 1919, so they are the exception here; most extensions run across the full rear width instead. Our side return extension page covers the build in detail, with build rates of £2,400 to £3,200 per m².
Double storey extensions in Hillingdon
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 Hillingdon often needs planning permission from Hillingdon Council. With 36% of homes here semi-detached or detached, the side of the house is often an option too. There are 31 designated conservation areas in Hillingdon (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- Party wall process explained, and the extension built to the award
- Levels, drainage and landscaping made good around the new build
- Flat and pitched roofs with rooflights or lanterns
VOA Council Tax stock of properties, March 2025, for all 32 statistical areas in Hillingdon. Counts rounded by the VOA.
Why Choose GS Renovation in Hillingdon
GS Renovation is a genuine end-to-end builder for Hillingdon extensions, not a middleman. We coordinate the design and build the foundations, the steel, the roof and the internal finish with one accountable team, and we know how the borough's interwar semis and their plots behave. With our founder's 30+ years on the tools, we deliver extensions that add real, lasting space.
- Foundation depth set after trial holes, drains and trees are checked
- Insulation and thermal detailing to current regulations
- Waste cleared as we go, not left piled up outside
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
The kitchen has been fitted to the high standard. Saaid was polite, professional, tidy, he pays attention to a little details that make huge…
Saiid did a complete refurbishment of our small bathroom. This involved ripping out the existing bath/shower, basin, toilet, pipework, and tiles and…
FAQ
Frequently Asked Questions about House Extensions Hillingdon
How much should a Hillingdon homeowner set aside for house extensions?
Set aside money for house extensions in Hillingdon under three headings, structure, trades and approvals, within £2,000 to £2,800 per m² for a rear extension (indicative), and you will not be caught out. That is how the UB8 quotation is laid out, so each element can be checked or deferred. The order also affects cash flow: drainage under the footprint is diverted before foundations are poured.
Does my rear extension in Hillingdon need planning permission from the council?
It depends on the size and your property. Many single storey rear extensions on Hillingdon semis are permitted development and need no full planning application, though larger ones may require prior approval. Double storey, wrap-around or front extensions, and side extensions in conservation areas, usually need planning permission from Hillingdon Council. Either way, building regulations apply and building control must inspect and sign off the work.
How deep will the foundations for my Hillingdon extension be?
There is no fixed depth. The engineer and building control decide from what is dug. The generous, planted plots in Ruislip and Ickenham often put trees and drains near the dig, and clay near roots can shrink, so footings near trees are often taken deeper. Building control inspects the trench before concrete goes in.
Can we stay in our Hillingdon home while the extension is built?
Usually, yes. The new shell goes up while the old rear wall stays in place, so the house stays sealed for much of the build. The disruptive stretch is when that wall is opened and the steel goes in, followed by joining floors, heating and electrics. If the kitchen moves into the extension, plan to be without one for that stage.
What happens to the drains under a Hillingdon extension?
They are surveyed before the design is fixed. A rear extension often sits over the house drain run and its inspection chamber; that chamber is moved or replaced so access is kept. If a public sewer runs under the footprint, Part H means the water company must consent before building over or near it.
Does a roof lantern affect the insulation rules for a Hillingdon extension?
Yes, the extension as a whole must meet current Part L standards, and glazing loses far more heat than an insulated roof. A large lantern or several rooflights may mean a better specification elsewhere. The designer checks this before building control approval, and the inspector sees the insulation before it is covered.
Where can a side extension sit on a house in Ruislip Village Conservation Area?
Back from the front. Hillingdon's Ruislip Village Conservation Area leaflet says side extensions should normally be set back from the original building line, so a side addition flush with the front wall starts on the wrong foot. Hillingdon also says planning applications for development in conservation areas should be supported by a heritage statement. Commission it alongside the drawings, not after them, because the set-back, the roof form and the choice of brick are exactly what it has to justify.
Why measure a Hillingdon extension's floor area before the building control application?
Because Hillingdon bands its charge by size. It has one charge for a domestic extension of less than 40m2, for full plans or building notice, and a higher one for a domestic extension of 40m2 to 60m2. A wrap-around that grows during design can cross from one band into the next. Ask the designer to state the measured floor area on the drawings and apply under the band it falls in. The charges in those tables apply to new applications deposited on or after 1st April 2026, so use the current table rather than an older estimate.
Could a large Hillingdon extension be liable for the Community Infrastructure Levy?
Check it if the scheme is large. In Hillingdon the CIL applies to all proposals that add 100m2 of new floorspace or an extra dwelling. A two-storey wrap-around can approach that area, and an extension laid out as a self-contained annex raises the extra dwelling question. Ask the planning agent to confirm in writing whether the scheme is chargeable and whether any relief has to be claimed before work starts. Hillingdon has applied its charging schedule to new developments since 1 August 2014.
Every Service, One Team
More GS Renovation Services in Hillingdon
One team for every GS Renovation service in Hillingdon:
Same Service, Nearby Areas
House Extensions Near Hillingdon
We carry out house extensions across Hillingdon and the surrounding areas. Explore a nearby location:
Ready to Start Your Hillingdon Project?
Free, no-obligation quote for house extensions in Hillingdon.