House Extensions New Malden
Single storey rear and double storey extensions in New Malden, 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 New Malden, where interwar semis and older terraces in KT3 often have the garden depth that makes rear, kitchen and side-return extensions worthwhile. We handle the groundworks, steelwork, roof and full fit-out, turning tired 1930s layouts into bright, open family space.
In New Malden, 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 New Malden: 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 New Malden
New Malden range: choose above
Rear and side-return extensions in New Malden
The classic New Malden extension pushes into the back garden or fills the narrow side passage of a 1930s semi to create a kitchen extension with a large kitchen-diner across the rear. Because the original back wall is load-bearing, we install steel beams sized by a structural engineer, then pour proper foundations and manage the groundworks first, checking for mature garden trees before we dig.
Some New Malden extensions fall under permitted development, while others need a full planning application to Kingston Council, and it depends on the size, height and position of your property, whether it has been extended before, and any local restrictions. We assess your specific KT3 home, and advise honestly which route applies before any drawings are commissioned.
Housing in New Malden
Around 7,070 homes make up New Malden on the valuation list; 31% are flats and 69% houses, and 33% date from before 1919, 33% from between the wars and 34% from after 1945. A rear extension on a semi in New Malden digs beside the attached neighbour, so one party wall notice is usual, and 31% of homes here are semi-detached.
Depth, garden and fee bands for a New Malden extension
Kingston's Residential Design SPD sets the two measurements a New Malden rear extension is drawn against. Single storey rear extensions should generally not exceed 3-3.5m in depth, and in all cases at least 50% of the rear garden should remain. On a long garden the depth figure limits the design first. On a short garden the garden figure can bite before it, so measure from the existing rear wall to the back boundary before briefing a designer. These are tests for a planning application; an extension built under permitted development is measured against the national limits instead.
Size also sets the building control charge. Kingston puts an above ground domestic extension greater than 10 m2 but not exceeding 40 m2 into one band, charged the same under full plans or building notice, so check where the drawn floor area falls before the design is frozen. The levy is a separate question. Kingston's CIL guidance says a domestic single storey extension of 30 square metres is not CIL liable because the extension is less than 100 square metres. For most single storey New Malden extensions that removes one cost line, but only once the floor area on the drawings confirms it.
Double storey and wrap-around builds in KT3
Wider interwar plots in New Malden often suit a wrap-around that combines a rear and side extension, or a double storey addition that adds a bedroom and en-suite over a bigger ground floor. These larger projects almost always need planning permission from Kingston Council rather than relying on permitted development, and we coordinate that planning route alongside the structural design.
Where the new build sits against the shared boundary of a semi, the Party Wall Act comes into play, so you serve notices on the adjoining owner before excavation begins, with the drawings we supply. From foundations and steel frame through roofing, glazing and the full internal fit-out of plastering, wiring, plumbing and decoration, one GS Renovation team sees the whole KT3 extension through to completion.
Kitchen extensions in New Malden
58% of the houses in New Malden 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 New Malden; the build figures are in the table above.
- Building control inspections at foundation, damp course and steel stages
- Side-return and rear extensions
- Drawings and the structural engineer's design coordinated for you
VOA Council Tax stock of properties, March 2025, for New Malden East and New Malden West. Counts rounded by the VOA.
The GS Renovation Difference in New Malden
Homeowners in New Malden choose GS Renovation because we manage the extension from the engineer's drawings to the final coat. We tell you plainly whether your KT3 project is permitted development or needs a planning application, give you the drawings for the party wall notices your house requires, and build the structure and fit-out with one accountable team. Our founder's 30+ years on the tools stands behind the work.
- Foundation depth set after trial holes, drains and trees are checked
- Structural engineer instructed and coordinated on your behalf
- Drainage diverted or built over with the right approval in place
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
George was brilliant. Lovely bloke, very reasonably priced and a perfectionist to boot. He completed our small kitchen renovation with care and great…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
FAQ
Frequently Asked Questions about House Extensions New Malden
Is the price of house extensions higher in New Malden than elsewhere in South West London?
The price of house extensions in New Malden is set by the housing rather than the postcode, within £2,000 to £2,800 per m² for a rear extension (indicative). Older construction takes more making good than recent work, and access at KT3 affects the labour line. GS Renovation prices the property in front of it, because the depth of neighbouring New Malden foundations decides how deep the new footings go, rather than applying a New Malden multiplier.
Will my New Malden extension need planning permission or is it permitted development?
Many single storey rear extensions on New Malden houses fall under permitted development, but double storey, wrap-around and larger builds usually need a full planning application to Kingston Council. We assess your KT3 home, its size limits and any prior extensions, then advise the correct route before any work begins.
Why might a New Malden extension need deeper foundations than expected?
Clay and trees. The London clay under this part of Kingston upon Thames shrinks and swells with moisture, and mature garden trees draw water from it, so the engineer and building control may call for deeper footings, or a reinforced or piled design near roots. The species and distance of nearby trees are noted at survey, because they fix the depth before the digger arrives.
What does building control look at during a New Malden extension?
It comes back at each hidden stage: open trenches ahead of the pour, new pipework while still visible, the slab and its membrane, the steel over the breakthrough, and the wall and roof insulation that Part L demands. Missing a visit means opening work up again. Kingston Council's final certificate is the document your conveyancer will want when the semi is eventually sold.
Does a New Malden rear extension involve the attached neighbour?
Usually, through the Party Wall Act. Digging foundations within 3 metres of the adjoining semi and below its footings needs a month's notice, and cutting into the party wall to seat a beam needs two months. The neighbour may consent or dissent, and a dissent leads to a surveyor's award. On the detached side, whether notice applies depends on how close that house stands.
How do we stop a New Malden extension darkening the middle of the house?
Bring light in from above. A deep kitchen-diner across the back of a semi leaves the old rear room far from any window once it is opened up, so a roof lantern or a row of rooflights over the join does the most work. Glazing counts against Part L, so larger areas of glass are balanced by better insulation in the roof and walls.
Is Kingston's fast track planning service open to a New Malden extension?
For a householder application Kingston offers a fast track service at a set fee, but it cannot fast track applications for listed buildings or properties in a conservation area, and the borough has 26 conservation areas. Check the address first. If the house is outside them and not listed, ask Kingston whether the scheme qualifies, because fast track can shorten the wait. If it is inside one, plan the programme around the standard timetable instead.
Is pre-application advice worth it before a New Malden extension is drawn?
Kingston offers householder pre-application advice for alterations and extensions as a remote meeting, written advice, or both, and aims to respond within 8 weeks of submission. That is a long wait for a plain rear extension inside the SPD guidance. It earns its time on schemes that go beyond it, such as a deeper extension or a two storey addition close to a neighbour's window, where the officer's early view can save a refused application.
What extra does Kingston want if a New Malden extension goes below ground?
Kingston's Residential Design SPD requires proposals for subterranean development to be accompanied by a Construction Method Statement, and says light wells should not exceed more than one storey underground. A lower ground room dug out at the back of a New Malden house therefore needs its excavation and propping sequence written down before planning is decided. Building control charges a below ground extension separately from one above ground.
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