Kitchen Extensions London
Rear, side return and wraparound kitchen extensions, designed and built by one team from the first drawings to building control sign-off.
Kitchen extension builders in London
A kitchen extension adds ground floor space at the back or side of the house so that the kitchen, the dining area and the garden doors work as one room. Alstruct designs and builds kitchen extensions across London: single-storey rear, side return, wraparound and double-storey.
One team takes the project from the first drawings to building control sign-off, and we coordinate the delivery and installation of your kitchen within the build programme. Every project is priced as a fixed-price, itemised written quote, built under a JCT contract and covered by our 10-year workmanship warranty. We hold CHAS Elite and Constructionline Gold accreditation and are members of the Federation of Master Builders (FMB).
At a glance: at mid to high specification, a kitchen extension in London typically costs £80,000–£160,000 for a single-storey rear extension, £65,000–£130,000 for a side return, £190,000–£380,000 for a wraparound and £170,000–£320,000 for a double-storey, including VAT and a typical allowance for professional fees. The kitchen itself (units, worktops and appliances) is a separate budget, typically £15,000–£60,000+. Allow 12–16 weeks on site for a single-storey kitchen extension. Full breakdown: kitchen extension cost guide.
Which kitchen extension suits your house
The house, the plot and how much of the ground floor you want to open up decide the type. On a Victorian terrace with a side alley, a side return is usually the best value; a wraparound gives the most kitchen-diner space. Prices are our mid and high specification ranges, including VAT; durations are time on site.
The four types compared
Single-storey rear extension
Builds out from the back of the house into the garden, typically by 20–40m². It suits most terraced and semi-detached houses and is the extension type most likely to go ahead without a full planning application. £80,000–£160,000; typically 12–16 weeks on site.
Side return extension
Fills the strip beside the back of a Victorian or Edwardian terrace or semi, typically 1.5–2.5 metres wide, so a kitchen 2.5–3 metres wide becomes a kitchen-diner 5–7 metres wide. Rooflights are almost always essential. £65,000–£130,000 for 15–25m²; typically 12–16 weeks on site.
Wraparound extension
Combines a rear extension with a side return infill to open up the whole ground floor, adding 40–80m². It suits period terraces and semis that have a side return. £190,000–£380,000; typically 16–22 weeks on site.
Double-storey extension
A kitchen-diner on the ground floor with one or two bedrooms and a bathroom above, sharing one set of foundations and one roof. £170,000–£320,000 for 40–70m²; typically 18–24 weeks on site.
Our house extensions page covers every type, and the single-storey rear extension and Victorian side return cost guides go into each in detail.
What a kitchen extension costs in London
The table shows our published mid and high specification ranges for London in 2026. They cover the building work, which delivers a finished shell ready for the kitchen install. Your quote will be a fixed price for your house and your drawings.
| Type | Typical size | Mid specification | High specification |
|---|---|---|---|
| Single-storey rear | 20–40m² | £80,000–£110,000 | £120,000–£160,000 |
| Side return | 15–25m² | £65,000–£85,000 | £90,000–£130,000 |
| Wraparound | 40–80m² | £190,000–£260,000 | £270,000–£380,000 |
| Double-storey rear | 40–70m² | £170,000–£230,000 | £240,000–£320,000 |
Indicative ranges for London in 2026. Figures include VAT at 20% and a typical allowance for professional fees. They do not include the kitchen units, worktops and appliances, furniture, landscaping or party wall surveyor costs.
The kitchen is a separate budget
The units, worktops and appliances are priced separately from the build, typically £15,000–£60,000+: from around £15,000 for a quality fitted kitchen to £60,000 or more for bespoke cabinetry, stone worktops and integrated appliances. Our side return guide puts a designer kitchen at £25,000–£60,000+.
The specification stays your choice. We can manage the installation as part of the main contract or as a nominated sub-contract supply, and either way we coordinate delivery and fitting within the build programme.
What moves the build price
After size, specification moves the price most. Our guide puts mid-range work at £2,500–£3,200/m² and high specification at £3,200–£4,500/m², and the gap is mostly glazing, kitchen and finishes.
Structure comes next. Removing a full rear wall needs a steel frame and temporary propping, typically adding £8,000–£20,000 depending on span, and deep excavation adds £5,000–£15,000 depending on ground conditions. A side return over shared drains may need the drainage diverted, and tight inner-London access and conservation area requirements add cost. The house extension cost guide sets out every line.
A fixed price, not a range
Get a fixed-price quote for your kitchen extension
Book a consultation or send us your drawings. We price the build as an itemised, fixed sum on a JCT contract, and every job carries our 10-year workmanship warranty.
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Design choices that make a kitchen extension work
Glazing, structure and layout are fixed on the drawings, and between them they set the daylight and much of the cost.
Glazing and rooflights
Glazing is where budgets swing most. Bi-fold or sliding doors to the garden make even a modest extension feel generous. Structural frameless glazing can cost 5–8 times as much per metre run as standard bi-fold doors, and Crittall-style screens and slimline aluminium frames sit at the premium end.
Rooflights or a lantern are the best way to light a deep-plan kitchen, especially on a terrace where you cannot add side windows. A quality rooflight is £2,500–£8,000, and a roof lantern adds £3,000–£8,000. At Evelyn Road, rooflights in the flat roof light the kitchen without the solar gain of a south-facing glazed elevation, and the neighbours' garden views are unaffected.
Steel, the island and the layout
Removing the entire rear wall for a fully open-plan space needs more steel, and sometimes a goalpost frame, than keeping a section of wall. A part-wall, a step or a change in ceiling height zones the space without closing it off. If you have the width, an island gives prep space, storage and a social hub; steelwork creates the wide spans that large islands need, so fix the island, sink and hob positions before the steel is ordered.
Utility space, services and flooring
A utility area or larder needs water and waste, so place it on the drawings too: moving services for the new layout is part of the build price, but changes made once work is on site are the biggest controllable cause of delay. Running the same floor through to the garden doors makes the whole space read as one.
How a kitchen extension project runs
- Consultation and brief. We discuss your brief, budget and the planning position for your address. Send any drawings or photos with your enquiry: the contact form takes PDF, JPG, PNG, HEIC and DWG files.
- Design and drawings. Our in-house architectural team carries out the measured survey and prepares the design and planning drawings, with 3D visualisations, typically over 4–8 weeks for a single-storey extension. If you already have an architect, we work from their drawings.
- Planning and party wall. Where planning permission is needed it adds 8–12 weeks; a Lawful Development Certificate takes up to 8 weeks. Building regulations drawings run alongside on the Full Plans route, and we serve party wall notices at the same time.
- Fixed-price quote and JCT contract. We issue a fully itemised quotation broken down by trade. The JCT Minor Works Building Contract gives a fixed price for the agreed scope, a defined programme and written variation instructions.
- Pre-construction. Typically 2–4 weeks. Long-lead items such as structural steelwork, windows and roof lanterns are ordered.
- Build. Demolition and groundworks (weeks 1–3), structural frame and walls (weeks 3–7), roof and weathertight (weeks 6–9), first fix (weeks 8–11), plastering and second fix (weeks 10–14), finishing and decoration (weeks 13–16). Kitchen and joinery installation typically takes place in weeks 12–14.
- Sign-off and handover. Building control carries out the final inspection and issues the Completion Certificate, which we obtain for you. Our 10-year workmanship warranty starts at practical completion; the full wording is in our terms and warranty.
How long a kitchen extension takes
On site, a single-storey rear or side return kitchen extension typically takes 12–16 weeks, a wraparound 16–22 weeks and a double-storey 18–24 weeks. From first meeting to handover, a single-storey project typically runs 6–10 months, because design, planning and building regulations account for 3–6 months before work starts. Where the extension is permitted development, it is typically 6–10 weeks from instruction to site start.
Most clients remain in their home throughout. Expect 1–2 weeks of higher disruption during the structural openings, and kitchen use may be disrupted for several weeks. The extension timeline guide covers each stage.
Planning, building regulations and party wall
Rear kitchen extensions
A single-storey rear extension is usually permitted development if, among other limits, it goes no more than 3m beyond the rear wall of the original house on a terraced or semi-detached house, or 4m on a detached house, is no more than 4m high, and covers no more than half the garden area of the original house. Flats and maisonettes do not have these householder rights.
Outside conservation areas, the larger home extension route allows up to 6m (terraced or semi-detached) or 8m (detached) through prior approval. In a conservation area a single-storey rear extension within the 3m or 4m limits can still be permitted development, but the larger home extension route is not available, and an Article 4 direction can remove the rights street by street. Where a project qualifies, we recommend a Lawful Development Certificate before work starts; the fee is £274.
Side return, wraparound and double-storey
A side return infill can be permitted development only if it is single storey, no wider than half the original house and no more than 3m beyond the rear wall of the main house. Many Victorian side returns are longer, so they need prior approval (outside conservation areas) or planning permission. In a conservation area every side extension, including a side return infill, needs planning permission, whether or not it can be seen from the road.
A wraparound counts as one extension that must meet both the rear and the side limits, so most need a householder planning application, and double-storey rear extensions almost always do.
Applications and building regulations
A householder planning application costs £548 and adds 8–12 weeks to the programme. Between September 2025 and August 2026, London councils approved 86.9% of rear extension applications, 85.8% of side and infill (side return) extensions, 88.2% of wraparound extensions and 78.0% of two-storey extensions, and the median decision took 8.0 weeks from validation (our 2026 London planning approvals study).
Building regulations are separate from planning, and a kitchen extension must meet them: structure, fire safety, insulation to Part L, drainage and ventilation. We use the Full Plans route as standard, so the technical drawings are approved before construction starts.
Party wall
A side return extension almost always triggers the Party Wall etc. Act 1996. A rear extension usually does only where it sits on the boundary, or where its foundations are within 3m of a neighbour's structure and go deeper than the neighbour's foundations. Notices are served one or two months before the start, and the neighbour has 14 days to respond.
If the neighbour consents in writing, no surveyor is needed, but the notice period still applies unless they also agree in writing to an earlier start. Otherwise surveyors agree a Party Wall Award. Surveyor costs are usually paid by the building owner (strictly, the surveyors decide): typically £800–£1,500 with a single agreed surveyor, or £800–£3,500 per neighbour where each side appoints its own. Our party wall agreement cost guide has the detail.
What is included
- In-house architectural drawings and 3D visualisations
- Planning application or Lawful Development Certificate, where required
- Building regulations approval and structural engineering calculations
- Party wall notices prepared and served
- Excavation, footings and a new insulated concrete slab
- Steel beams to open up the rear wall, blockwork and the new roof
- Bi-fold or sliding doors, rooflights or a lantern, all double-glazed
- Electrics, plumbing and underfloor heating or radiators
- Plastering, screed and decoration, ready for the kitchen
- Kitchen delivery and installation coordinated within the programme
- Building control inspections and the Completion Certificate
- Full project management and our 10-year workmanship warranty
Not included: the kitchen units, worktops and appliances, furniture, blinds and curtains, landscaping and party wall surveyor costs.
Kitchen extensions in our published projects
Each of these case studies includes an extension that forms a new kitchen-dining space, as part of a wider renovation; more are in our projects portfolio.
Areas we cover
We build kitchen extensions across London. Each area page covers the local house types and conservation areas.
- West London: Chiswick, Ealing, Notting Hill, Acton, Hammersmith, Shepherd's Bush, Kensington
- South-west London: Tooting, Balham, Clapham, Battersea, Wandsworth, Putney, Fulham, Barnes, Wimbledon, Richmond, Twickenham
- South and south-east London: Greenwich, Blackheath, Lewisham, Dulwich, Peckham, Brixton, Croydon, Bromley
- North London: Islington, Highgate, Hampstead, Crouch End, Muswell Hill, Stoke Newington, St John's Wood, Finchley, Barnet, Cockfosters, Enfield
- East London: Hackney, Stratford, Walthamstow, Leytonstone, Wanstead, South Woodford, Woodford Green, Chingford
We work across every London borough; see all areas.
Frequently Asked Questions
How much does a kitchen extension cost in London?
At mid to high specification, a single-storey rear kitchen extension in London typically costs £80,000–£160,000, a side return £65,000–£130,000, a wraparound £190,000–£380,000 and a double-storey £170,000–£320,000. These figures include VAT and a typical allowance for professional fees. The kitchen itself, meaning the units, worktops and appliances, is a separate budget, typically £15,000–£60,000+. Once the drawings are agreed, we give you a fixed-price, itemised quote rather than a range.
Does the price of a kitchen extension include the kitchen?
No. Our published figures cover the building work: groundworks, structure, glazing, roof, electrics, plumbing, heating, plastering and decoration, delivering a finished shell ready for the kitchen install. The units, worktops and appliances are a separate budget, typically £15,000–£60,000+ depending on specification. We can manage the installation as part of the main contract or as a nominated sub-contract supply, and we coordinate delivery and fitting within the build programme.
What is the best kitchen extension for a Victorian terrace?
A side return is usually the best value. It fills the narrow strip beside the back of the house, typically 1.5–2.5 metres wide, so a kitchen 2.5–3 metres wide becomes a kitchen-diner 5–7 metres wide. Combined with a rear extension it becomes a wraparound, which gives the most kitchen-diner space. Rooflights are almost always essential, and party wall notices are almost always required.
Do I need planning permission for a kitchen extension in London?
Often not for a single-storey rear extension: up to 3m beyond the rear wall of the original house on a terraced or semi-detached house, or 4m on a detached house, and no more than 4m high, it is usually permitted development. That can still apply in a conservation area, unless an Article 4 direction removes the rights. A side return can be permitted development only if it extends no more than 3m beyond the main rear wall, and never in a conservation area.
How long does a kitchen extension take?
On site, a single-storey rear or side return kitchen extension typically takes 12–16 weeks, a wraparound 16–22 weeks and a double-storey 18–24 weeks. Before that, allow 4–8 weeks for design and, where planning permission is needed, a further 8–12 weeks. From first meeting to handover, a single-storey project typically runs 6–10 months; a permitted development project is typically 6–10 weeks from instruction to site start.
Will I need a party wall agreement for a kitchen extension?
A side return extension almost always triggers the Party Wall etc. Act 1996. A rear extension usually does only if it sits on the boundary, or its foundations are within 3m of a neighbour's structure and go deeper than theirs. If the neighbour consents in writing, no surveyor is needed. Otherwise surveyor costs are typically £800–£1,500 with one agreed surveyor, or £800–£3,500 per neighbour, usually paid by the building owner.
Do you build kitchen extensions in Chiswick, Tooting, Ealing, Notting Hill and Greenwich?
Yes. We build kitchen extensions across London, working across every London borough from our office in South Woodford, E18. Each area page covers local house types and conservation areas, and our in-house architectural team checks the permitted development position for your address and prepares any application to the council. Send drawings or photos through the contact form, or call 020 8080 8240.
Can we live in the house while the kitchen extension is built?
In most cases, yes. The works are largely external until the wall between the house and the new extension is opened up near the end of the build. Expect 1–2 weeks of higher disruption during the structural openings, when a temporary hoarding protects the interior until the new structure is weathertight. Kitchen use may be disrupted for several weeks, and we maintain access to your home throughout.