How much does a kitchen extension cost in South West London in 2026?
Honest price ranges for rear extensions, side returns and wraparounds — plus what drives the cost and how kitchen fit-out fits into the budget.
By Distinct Spaces · Updated June 2026 · 7 min read
A kitchen extension is one of the most transformative things you can do to a Victorian or Edwardian terraced house in South West London. Opening up the back of the ground floor — extending into the garden, filling in the side return, or doing both — creates the kind of open-plan kitchen-diner that defines how families want to live.
It's also one of the more expensive home improvements. The structure, glazing, services and finishes all add up quickly. This guide breaks down realistic costs so you can plan your budget properly.
Price ranges by extension type
Kitchen extensions in South West London generally fall into three configurations:
Small rear extension (10–15 m²) — £30,000 to £45,000
A single-storey extension projecting 3–4 metres into the garden. Adds a generous kitchen-dining area. Often permitted development. Build cost only — kitchen furniture, appliances and decoration are separate.
Side return extension (15–25 m²) — £35,000 to £60,000
Fills in the narrow alleyway alongside a Victorian terrace that runs between the rear of the house and the boundary wall. Transforms a dark, cramped kitchen into a wide, light-filled space. Common in Twickenham, Surbiton and Kingston terraces.
Wraparound extension (25–50 m²) — £55,000 to £120,000
Combines a rear extension with a side return into an L-shaped footprint. The most dramatic transformation — creates a large open-plan ground floor with room for kitchen, dining and living. Usually requires planning permission.
These are structural build costs per square metre of £2,200–£3,300, which is the realistic range for quality construction in SW London in 2026. They include foundations, structure, roof, glazing, electrics, plumbing to connection points, and plastering. They do not include the kitchen itself.
What the kitchen fit-out adds
The build cost and the kitchen cost are two separate budgets, and it's easy to underestimate the second one. A kitchen for a newly extended space in South West London typically costs:
- Entry-level (IKEA or equivalent): £6,000–£12,000 supply and fit
- Mid-range (Howdens, Magnet, independent joiner): £15,000–£30,000
- High specification (bespoke or premium brand): £35,000–£80,000+
The kitchen cost depends on size, materials, appliances, and worktop choice. Quartz or granite worktops, integrated appliances, and handleless doors all add to the price. It's worth deciding on your kitchen specification before you finalise the extension design — the layout of sockets, plumbing points and extract ducting needs to be agreed before walls go up.
What drives the build cost up
Glazing. A large roof lantern or a full-width set of bifold or sliding doors is one of the most popular choices for kitchen extensions — and one of the most significant cost items. A quality aluminium roof lantern over 3×2m costs £3,000–£6,000 for the unit alone, before installation. Bifold doors across 4m of opening add £6,000–£10,000. These are worth doing properly — cheap glazing leaks, condenses and fails.
Structural steels. Opening up the rear wall of a house typically requires a steel beam spanning the full width of the new opening, supported on padstones or new columns. A structural engineer designs this; the steel is fabricated and installed during the build. This is a fixed cost regardless of specification — budget £3,000–£6,000 for the engineering and steel work.
Underfloor heating. A popular choice for a new kitchen extension — warm feet, no radiators taking up wall space. Wet underfloor heating (water-fed pipes in a screed) costs more to install than electric, but costs less to run. Budget £80–£120/m² for a wet UFH system installed as part of the build.
Foundation type. Ground conditions in South West London vary. Most extensions use traditional strip foundations. But if you're close to trees (particularly in areas like Kew or Richmond Park edges), or if the soil has significant clay content, a structural engineer may specify deeper or wider foundations to manage movement risk. This adds cost and time.
Flat roof vs pitched vs lantern. A flat roof with a lantern or roof light is the most common choice for a rear extension and the most cost-effective structurally. A pitched or mono-pitch roof costs more to build but may be required in conservation areas or where the extension needs to match the existing roof character.
Total budget: what to allow
A realistic total budget for a kitchen extension in South West London — structure plus kitchen fit-out plus decoration — typically looks like this:
Modest side return + entry-level kitchen: £45,000–£65,000 total
Mid-size rear extension + mid-range kitchen: £65,000–£95,000 total
Wraparound + premium kitchen: £110,000–£180,000+ total
These ranges assume good but not extravagant specifications. The biggest variables are glazing, kitchen specification, and whether planning permission adds delays and design fees to the process.
What a fair quote looks like
A solid quote for an extension should be itemised: groundworks and foundations, structure, roof, external walls, glazing, internal finishes, electrics, plumbing, and any kitchen-specific prep work broken out separately. Lump-sum quotes with no breakdown make cost comparison and change management impossible.
At Distinct Spaces we handle the full build — from structural design and building regulations through to decorated, ready-to-fit shell. We coordinate the kitchen fit-out to follow on immediately so there are no gaps between trades and no delays waiting for contractors who aren't booked.
Planning a kitchen extension? We do free site visits and give you a proper breakdown — no obligation.
Get in touch