Honest pricing for Hampstead house extensions
Online cost calculators use national averages that don't reflect Hampstead, NW3 or NW6 reality. Build costs in North West London are higher than the UK average — but the value uplift is proportionally greater too.
The prices on this page come from our actual recent projects across Hampstead, Belsize Park, West Hampstead, Swiss Cottage and Kilburn. They include everything: foundations, structural steel, brickwork, roofing, windows, internal finishes and Building Control.
What affects the price? Five factors: (1) size — measured in square metres of additional floor area; (2) spec level — standard vs premium finishes; (3) structural complexity — how many walls are removed; (4) access — rear-only access costs more for materials delivery; (5) planning — conservation areas add design costs.
What's included in our prices
Every price is all-inclusive. No hidden extras. Here's what you get as standard.
Foundations & Groundwork
Strip or trench fill foundations, damp-proof course, sub-floor drainage, and ground floor slab. All to Building Regulations.
Structural Steelwork
Chartered engineer calculations, steel beam design. All steel fabricated and installed — RSJs, lintels, padstones and structural openings.
Brickwork & Roofing
Matching or complementary brickwork, flat roof (EPDM/GRP) or pitched roof as designed. Skylights, lantern roofs or rooflights included where specified.
Windows & Doors
Bi-fold, sliding or French doors. All glazing units, window frames and hardware. Aluminium or timber as designed.
Full Internal Finish
Plastering, electrics, plumbing, flooring, tiling, decoration. Kitchen fitting available as an add-on. Ready to move furniture in.
Building Control
Full Building Regulations application, all inspections managed, completion certificate at handover. We handle everything.
"Hampstead Renovations transformed our cramped Victorian kitchen into a stunning open-plan kitchen-diner with bi-fold doors to the garden. The team managed all the planning and party wall issues, and the quality of the build was outstanding."Sarah & David MitchellHomeowners, Hampstead NW3
House extension price guide — Hampstead, NW3 & NW6
Fixed prices from recent local projects. Written quote provided after a free site survey.
| Extension Type | 2026 Price Range |
|---|---|
| Side-return extension (12–18 sqm) | £38,000 – £70,000 |
| Single-storey rear (15–25 sqm) — standard spec | £48,000 – £80,000 |
| Single-storey rear — premium spec | £80,000 – £120,000 |
| Wrap-around rear + side — standard | £70,000 – £110,000 |
| Wrap-around — premium spec | £110,000 – £160,000 |
| Two-storey rear extension | £90,000 – £170,000 |
| Kitchen extension with island | £55,000 – £100,000 |
| Glass box / frameless glazing | £65,000 – £130,000 |
| Orangery-style extension | £60,000 – £110,000 |
| Bi-fold doors (set of 3–5 panels) | £3,500 – £8,000 |
| Underfloor heating | £2,500 – £5,000 |
| Lantern roof / large skylight | £2,000 – £6,000 |
All prices exclude VAT. Prices reflect Hampstead, NW3 and NW6 build costs as of 2026. We provide a fixed, all-inclusive price after a free site survey. Kitchen units/fittings are additional.
House extension cost FAQ
NW London labour rates are higher, many properties are in conservation areas requiring specialist design, and access can be challenging. However, the value uplift (£100,000–£350,000) far exceeds the build cost.
Standard: quality windows, standard brickwork, painted plaster, standard electrics. Premium: bi-fold doors, underfloor heating, Porcelanosa/similar tiling, bespoke joinery, mood lighting, smart home integration.
No. Our quote is fixed and all-inclusive. The only additions would be things you choose to upgrade after signing. Kitchen units are quoted separately as most clients have a preferred supplier.
As a rule of thumb: £2,500–£3,500/sqm for standard spec and £3,500–£5,000/sqm for premium. But this varies significantly by extension type and structural complexity.
Book a free site survey. We visit, measure, assess structural requirements, check planning, and provide a fixed written quote within 5 working days. No obligation.
We offer staged payments linked to milestones — typically 4–5 stages. You only pay for completed work. 10% booking deposit to secure your start date.
Book a free extension survey & quote
Book a free site survey — we visit your property, measure everything, check planning constraints, and provide a fixed written price within 5 working days. No obligation.
Unit 3, Palace Court, 250 Finchley Road, Hampstead, London NW3 6DN
Mon–Fri 9am–8pm · Saturday 9am–6pm · Sunday by appointment
Company Reg: 16838595 · £10M Insurance (Aviva) · FMB Member · TrustMark