Kitchen and house extensions in London.
Planning to handover · a rear dormer and a full-width rear extensionCompleted work, photograph
Rear, side return and wraparound extensions for London houses, from feasibility to handover.
An extension changes the rooms it joins, too.
A house extension adds space at the rear or side, usually for the kitchen. We are NU Projects, design and build in Fulham SW6 since 2010. A rear extension runs £235 to £460 a sq ft, construction only. A side return runs £215 to £425 a sq ft. Call 020 7731 6841, and a budget estimate typically follows within seven days.
We take an extension from feasibility to handover. Planning, architecture, structural design and cost planning happen first. Construction follows under the same contract.
A side return fills the passage beside the rear projection. A rear extension runs out into the garden. A wraparound does both, for the largest change.
Daylight is planned before the glazing. A badly placed roof can darken the rooms you already have.
Traditional and modular routes are both assessed, then we tell you which suits. Most rear extensions also change the existing ground floor. We price the new area and the reworked rooms separately.
Already have an architect or designer? We build to their design, and work with them through to handover.
Jackie, in Fulham, had a single storey rear extension built. The verdict: “I am extremely pleased with the quality of the works.”
What the work includes
- Rear, side return and wraparound extensions
- Two-storey extensions, tested as one building
- Feasibility, planning and structural design in one team
- New area and existing rooms priced separately
- Traditional or modular construction, assessed for your site
- Construction and interior fit-out in one contract
- House extensions by area
- House extensions in Fulham, House extensions in Chelsea, House extensions in Kensington, House extensions in Clapham, House extensions in Notting Hill
- What it costs
- See a range in a minute. Then send us the address for a proper number. Open the calculator
- Where we work
- Fulham, Chelsea, Kensington, Knightsbridge, Belgravia, Mayfair, Notting Hill and Holland Park, Chiswick, Wandsworth, Putney and Barnes, Hampstead and St John’s Wood, Weybridge, Cobham and Oxshott, South Kensington, Marylebone, Bayswater and Maida Vale, Pimlico and Westminster, Battersea and Clapham, Richmond, Twickenham and East Sheen, Islington, Highgate and Primrose Hill, Greenwich, Dulwich, Camden, Wimbledon, Bermondsey, Brixton, Ealing, Acton, Hammersmith and Brook Green, Earl’s Court, Queen’s Park and Kensal Rise, Fitzrovia and Bloomsbury
We price the new area and the reworked rooms separately. So you see both.
From the first visit to the garden doors.
- 01
The house and the garden
A measured survey of the ground floor, the drains and the boundaries.
- 02
Side return, rear or wraparound
The options drawn and priced, with the daylight tested for each.
- 03
Structure and services
Steel, foundations, drainage, heating and lighting settled on the drawings.
- 04
Consents and notices
Planning or permitted development, building control and party wall notices handled.
- 05
The cost plan, then one contract
A price built line by line from the drawings. Provisional sums named, not buried.
- 06
Build, reports and handover
A report every week, with photographs. Then a defects period and aftercare.
Ten checks before you appoint an extension builder.
- 01
Comparable completed extensions
Ask for finished work on the same kind of house. A garden room says little about a side return.
- 02
Who designs the structure
Ask who designs the steel and checks it. Then ask how the house is propped while the wall is out.
- 03
The planning route for your address
Previous extensions, conservation status and an Article 4 direction all change the answer.
- 04
Party wall notices
Building on or near a boundary engages the Party Wall Act. Ask who serves the notices, and when.
- 05
Where the daylight comes from
Ask for the daylight strategy, not the glazing schedule. Where the glass goes matters most.
- 06
Drainage and levels
Ask where the falls and manholes go. Ask who checks for a public sewer.
- 07
Services in the new space
Underfloor heating, extraction and lighting go in before the screed. Ask who designs them.
- 08
Glazing lead times
Large sliding doors take months to make. Ask for the lead time in writing.
- 09
How the kitchen is coordinated
Ask who fits the kitchen drawings to the structure, the services and the floor.
- 10
What is in the price
Glazing, kitchen, joinery, external work, fees, contingency and VAT should each be named.
What an extension costs in London.
£235 to £460a sq ft, construction only. Our rear extension band.
£215 to £425a sq ft, construction only. Our side return band.
£160k to £250kRear kitchen extension. A project total, from our 2026 cost guide.
£140k to £220kSide return extension. A project total, from our 2026 cost guide.
£200k to £320kWraparound extension. A project total, from our 2026 cost guide.
£220k to £400kTwo-storey extension. A project total, from our 2026 cost guide.
Which figure applies depends on the house, the glazing and the finish.
Reworking the existing kitchen and rooms is priced as its own line.
Professional fees, statutory costs, party wall, contingency and VAT are separate. Ranges are guide prices, not fixed quotations.
Extensions we designed and built.
What owners ask before they extend.
Further reading, from the journal
Is a side-return extension right for my house?
We test the gain in usable width against daylight, circulation and garden access. Extending to the boundary is not always the right answer for every home.
A side return runs £215 to £425 a sq ft, construction only.
Can I build a rear or double-storey extension?
The answer depends on planning context, property size, neighbour effects and structural feasibility.
We test a two-storey addition as one whole building. This includes how the new upstairs rooms connect.
A rear extension runs £235 to £460 a sq ft, construction only.
What if a public sewer runs beneath the proposed extension?
We check the sewer position and ownership before design proceeds. Thames Water advises agreement is often needed within three metres of a public sewer. The same applies within one metre of a public lateral drain. Planning permission does not provide that consent.
Will an extension make the middle of the house dark?
It can, depending on depth, roof form and layout.
We test the existing rooms as well as the new space. Openings and circulation are used to spread useful light throughout.
Should the garden be designed with the extension?
We coordinate external levels, drainage, views, thresholds and lighting with the building.
Leaving the garden until the end can undermine your internal layout and access.
How much does a kitchen extension cost in London?
Our 2026 cost guide puts a rear kitchen extension at £160k to £250k.
That is a project total, before fees, contingency and VAT.
Built per square foot, a rear extension runs £235 to £460.
Do I need planning permission for an extension?
Some extensions are permitted development and some are not.
Previous extensions, conservation status and an Article 4 direction all change the answer.
We check the route against the property, not the street.
Will you build to my own architect’s design?
Yes. Already have an architect or designer? We build to their design.
We price their drawings line by line, then work with them through to handover.
Tell us about the extension.
Your name and one way to reply are enough. It goes straight to the studio.
- Already have an architect or designer? We build to their design. Working with your designer