Kitchen Extension Costs in Greater London: Full Breakdown

If you're thinking about extending your kitchen in London, the first question on your mind is probably "how much is this actually going to cost me?" I've been building extensions across Greater London for over two decades, and I'll give you the straight answer: a kitchen extension in 2026 typically costs between £45,000 and £120,000, depending on size, specification, and where in London you're building. Let me break down exactly where that money goes.

The Real Cost Breakdown

I've seen too many homeowners get caught out by online estimates that quote £1,500 per square metre. That might work in some parts of the country, but in London? You're looking at £2,200 to £3,500 per square metre for a properly built, fully finished kitchen extension. Here's why.

Rear vs Side vs Wraparound: What's the Difference?

Rear Extension (3-4 metres)

This is the most common type I build across London terraces. You're looking at 12-20 square metres typically, coming in at £35,000 to £65,000 for the shell, or £55,000 to £90,000 fully finished with a mid-range kitchen. Most rear extensions in zones 2-4 can be done under Permitted Development, saving you a few thousand in planning fees and a couple of months waiting.

Side Return Extension

If you've got a Victorian or Edwardian terrace with that narrow alley down the side, a side return extension typically adds 8-15 square metres. These are fiddly to build – access is tight, and you're often working around existing drainage. Budget £30,000 to £55,000 for the build, though the kitchen and finishing can easily match that again.

Wraparound Extension

Combining a rear and side return into an L-shape is where you really transform a property. You're adding 20-35 square metres, and the costs reflect that: £70,000 to £120,000 or more. In boroughs like Hackney, Islington, or Wandsworth, I regularly see wraparound projects hitting £150,000 once you've factored in a high-spec kitchen and landscaping.

Hidden Costs Most People Miss

I always tell my clients to budget an extra 15-20% contingency. Here's what catches people out:

• Party wall agreements: If you're building up to or on the boundary, you'll need a party wall surveyor. Budget £700-1,500 per neighbour, and that's if they're cooperative.
• Building regulations application: £500-900 for a full plans application in most London boroughs.
• Structural engineer: £400-800 for calculations and beam specifications.
• Architectural drawings: £1,500-4,000 depending on complexity and whether you need planning.
• Thames Water build-over agreement: If there's a public sewer within 3 metres of your foundations, expect surveys and potential diversions costing £500-3,000.
• Tree root issues: London clay and mature trees mean deeper foundations. A trial pit might reveal you need piled foundations, adding £5,000-15,000.
• Asbestos: Pre-1990s properties often have asbestos in soffits, old boiler flues, or artex. Removal typically costs £500-2,000.
• Skip hire and parking suspensions: A skip on the road in most London boroughs costs £40-80 per day for the suspension permit alone, plus the skip hire itself.

How Long Does It Actually Take?

A straightforward rear extension takes 10-14 weeks from breaking ground to completion. Here's a realistic timeline:

• Weeks 1-2: Groundworks, foundations, drainage
• Weeks 3-4: Brickwork up to roof level, steels installed
• Weeks 5-6: Roof, windows, doors – building is watertight
• Weeks 7-8: First fix electrics, plumbing, plastering
• Weeks 9-10: Second fix, flooring, decoration
• Weeks 11-12: Kitchen installation, snagging

Add 8-12 weeks before that for design, planning (if needed), building regs approval, and getting quotes. From first phone call to moving furniture back in, you're looking at 5-7 months minimum.

Planning Permission vs Permitted Development

Most single-storey rear extensions in London fall under Permitted Development rights, meaning no planning application needed. The limits are:

• 3 metres depth for attached houses (terraces, semis)
• 4 metres depth for detached houses
• Maximum 4 metres height
• No more than half your original garden covered by extensions

However, you lose PD rights in conservation areas (much of inner London), if you have an Article 4 direction, or if your property is listed. You'll also need full planning for anything over the size limits, two-storey extensions, or if you want to go closer to the boundary than 2 metres at height.

Even under PD, I always recommend getting a Lawful Development Certificate (£100-250). It proves to future buyers that the work was legal – solicitors ask for this during house sales.

Is a Kitchen Extension Worth It in 2026?

Here's my honest view: a well-designed kitchen extension typically adds 1.5 to 2 times its cost to your property value in most London areas. A £70,000 extension on a £600,000 terrace in Lewisham or Walthamstow could realistically add £100,000-140,000 to the sale price.

But value isn't just about numbers. If you're planning to stay for 5+ years, that open-plan kitchen-diner with doors onto the garden transforms how you live. You'll use it every single day.

Where I'd be cautious: if you're already at the top of prices for your street, or if the house has fundamental issues (subsidence, short lease, terrible location), an extension won't fix those problems.