What's the cheapest kitchen extension in London?

A side return extension is typically the cheapest London kitchen extension type — £55,000–£75,000 for a small (8–10m²) side return with a basic-finish kitchen. It uses the existing rear wall, infills a narrow alley with simple structure, and creates a useful kitchen-diner footprint without major demolition.

Is a 6m rear extension worth the extra over 4m?

A 6m rear extension under the Larger Home Extension prior approval scheme costs roughly £15,000–£25,000 more than a 4m extension on the same property — for around 6–10m² extra floor area. The value uplift is typically £20,000–£40,000 on the additional space, so the ROI is positive in most zones. The prior approval scheme adds 6–10 weeks to the planning timeline.

Does a kitchen extension add value?

Yes — a well-executed kitchen extension typically adds £90,000–£160,000 in value on a London property (zones 2–4), creating a positive return over the £75,000–£130,000 build cost. The open-plan kitchen-diner is now expected by buyers in the £700k–£1.5m bracket, so a kitchen extension often moves a property from 'dated' to 'turnkey' in the eyes of buyers.

How long does a kitchen extension take to build?

10–16 weeks on site for a standard 4m rear extension. Add 8–12 weeks for design, building regs, party wall and planning/LDC. Total project: 18–28 weeks from first consultation to handover. Side return extensions are slightly faster (10–14 weeks on site); wraparounds take longer (16–20 weeks).

Kitchen Extension Cost London 2025 — Real Prices

How Much Does a Kitchen Extension Cost in London?

A kitchen extension in London costs £65,000–£140,000 in 2025 for a single-storey rear or side return extension with a new fitted kitchen. A small side return (8–12m²) starts around £55,000. A standard 4m rear with new kitchen runs £90,000–£120,000. A wraparound extension (15–25m²) with premium kitchen runs £120,000–£180,000. Prices vary by borough, glazing spec and kitchen tier.

What's included in a kitchen extension cost

A complete kitchen extension price includes: design and architectural drawings, structural engineering, building regulations Full Plans application and fees, Lawful Development Certificate (or full planning if needed), party wall notices and surveyor co-ordination, demolition of existing rear wall and any small outbuildings, foundation excavation and concrete (typically 1m deep on London clay), brick/block superstructure with insulated cavity, steel beams over the new opening, flat or pitched roof structure with insulation to current Part L (typically 150mm PIR), bifold or slider glazing (typically 3–4m wide), 1–2 rooflights, full internal plaster and decoration, underfloor heating and screed (or engineered floor), full electrical first and second fix, full plumbing including new drainage connections, fitted kitchen (cabinets, worktops, sink, tap, integrated appliances), splashback and tiling, full clean and snagging, building control completion certificate. Excluded typically: party wall surveyor fees (£700–£2,000), bespoke joinery, premium worktops above the included tier.

Cost breakdown by extension type

A side return extension (infilling the existing side alley, 8–14m²) typically £55,000–£85,000 in zones 2–4 with a mid-range kitchen. A small rear extension (3m deep, 12–18m²) £75,000–£105,000. A standard 4m rear extension (16–24m²) £90,000–£125,000. A larger 6m rear under prior approval (24–35m²) £105,000–£145,000. A wraparound combining side and rear (20–35m²) £120,000–£180,000. A double-storey rear (typically only built where bedroom + kitchen needed, 35–50m² across two floors) £155,000–£235,000. These prices reflect typical London zones 2–4 in late 2025 with mid-range kitchen (£15,000–£25,000 kitchen tier) and aluminium bifolds. Outer London 8–12% lower; inner London / premium boroughs 8–15% higher.

What changes the price most

Five factors most commonly move kitchen extension prices. (1) Kitchen tier — a budget kitchen at £8,000–£12,000 vs a mid-range Howdens/DIY Kitchens at £15,000–£25,000 vs a Magnet/Wickes premium at £25,000–£40,000 vs a bespoke joiner at £45,000–£80,000+. The kitchen is often 15–25% of total project cost. (2) Glazing — standard bifolds £8,000–£12,000 for 3.5m, premium aluminium £15,000–£22,000, frameless sliders or Crittall steel £20,000–£35,000. (3) Floor — engineered oak £55–£90/m², porcelain tile £75–£120/m², premium stone £140–£220/m². (4) Structural complexity — corner steel posts, lintels over existing openings and difficult ground conditions (made ground, tree roots) add £5,000–£20,000. (5) Borough labour rates and party wall complexity.