House
extensions
in West Hampstead, NW6
Architects, Engineers, Surveyors & Builders Under One Roof.
One Studio. One Contract. One Team.
RICS surveying support for party walls, licence to alter, conservation-area works & neighbour mattersWe design and build West Hampstead house extensions across West End Lane, Fortune Green Road, Aberdare Gardens - side-return, rear, wraparound and double-storey additions for Victorian terraces, Edwardian villas and Large Mansion Blocks where planning strategy, conservation detailing, Party Wall sequencing and structural engineering need handling properly.
House Extensions in West Hampstead: What You Need to Know
Every house extension project in West Hampstead is designed to respect the West End Green Conservation Area and the character of Victorian terraces, Edwardian villas, large mansion blocks. Our in-house RIBA Chartered Architects handle Camden planning applications, our chartered structural engineers specify any load-bearing work, and our directly-employed trades deliver the build under one fixed-price contract. We coordinate Building Control, Party Wall awards where needed, and all certifications through to handover.
West Hampstead properties generally benefit from more relaxed planning controls, with many extensions achievable under permitted development rights. We assess the planning route at your free site visit.
Popular residential area with excellent transport (three railway stations) and a growing restaurant scene along West End Lane. Mix of Victorian and Edwardian housing with modern developments. Side-return extensions are particularly popular in West Hampstead's terraced streets, transforming narrow kitchen spaces into full-width open-plan living areas connected to the garden.
Local character & heritage: extending in West Hampstead
West Hampstead (NW6, Camden) is characterised by its red-brick Edwardian mansion flats — Cholmley Gardens, Compayne Gardens, Broadhurst Gardens — and the leafy “gardens” streets of Victorian and Edwardian terraced houses and villas that surround them.
The split between flats and houses shapes the work. The family villas and terraces on streets like Crediton Hill and Dennington Park Road suit classic side-return and rear extensions to create open-plan kitchen-diners; the mansion flats are about internal reconfiguration and adapting the flat layout under the lease. West Hampstead's conservation areas mean most external work goes through a full Camden application.
As across much of NW6, a large share of homes are leasehold mansion flats, so the freeholder's consent and the lease sit alongside planning, and right-to-light and party-wall issues arise on the tighter terraced plots. We scope tenure and neighbour matters early.
West Hampstead heritage & architecture: Cholmley Gardens · Compayne Gardens · Broadhurst Gardens · Converting large villas · Edwardian mansion flats · Adapting the mansion flat · Crediton Hill · Best family-home streets
West Hampstead is a dense quarter of Victorian and Edwardian building gathered around West End Lane, and its side streets — Fortune Green Road, Mill Lane, Sumatra Road, the Gardens streets — hold exactly the housing that rear extensions were made for: rows of bay-fronted terraces interleaved with Edwardian villas. These are the projects where a modest addition re-plans the whole ground floor.
The conservation cover is a patchwork rather than a blanket. Fortune Green, West End Green and Mill Lane conservation areas protect the best streets, with Camden's Article 4 controls scrutinising external change; the West End Green designation — its appraisal adopted in February 2011 — centres on West End Lane and the Green, reaching from Finchley Road in the north down to the Thameslink station. Whether your house falls inside one changes the consent route, not the ambition.
Budgets start from the Camden headline of £71,250–£112,500 excluding VAT for a rear extension and £90,000–£120,000 for a side return. What is distinctly local is the logistics: West End Lane's busy spine and the three railway lines threading the area shape deliveries, parking and site set-up, and we programme around them.
House Extensions in West Hampstead: Applied to the Local Stock
West Hampstead's local conservation designation is the West End Green Conservation Area (appraisal adopted 28 February 2011), centred on West End Lane and West End Green and bounded by Finchley Road to the north and West Hampstead Thameslink station to the south; part of West Hampstead town centre lies within the conservation area. London-wide indicative market band for wraparound extension: £100,000–£200,000 (source VAT treatment unstated, shown as an indicative market band, not a normalised ex-VAT figure) (Resi wraparound extension guide, 2025).
Sources: Camden Council, West End Green Conservation Area Appraisal and Management Strategy (adopted 28 February 2011) (2026); Wraparound extension (Resi wraparound extension guide, 2025) (2026)
What a House Extension Involves
An extension reshapes how the whole ground floor works, not just how big it is — the new structure, the opening into the existing house, the kitchen and the garden connection all have to be designed as one move. We take each project from feasibility drawings through consents, structure and fit-out under a single fixed-price contract. Most extensions we build include the scope below.
- Rear extensions — single-storey additions that open the back of the house to the garden
- Side-return & wraparound — infilling the side alley of a terrace, alone or combined with a rear addition
- Double-storey — new bedrooms or bathrooms above the ground-floor addition, designed to sit comfortably with the original roofline
- Foundations & steel — groundworks, beams and the opening into the existing house, engineered by our own structural team
- Glazing — rooflights, glazed roofs and slim-framed sliding or bi-fold doors specified for light and thermal performance
- Kitchen integration — the kitchen layout planned with the architecture from the first drawing, not squeezed in afterwards
- Services & heating — electrics, plumbing, drainage and underfloor heating built into the new floor
- External works — patio, drainage connections and garden reinstatement completed within the contract
How We Run Your Project
Six stages, with the consents and engineering settled before the first spade goes in.
- Feasibility visit — we assess the site, the boundaries and your brief, and identify the right consent route for your property.
- Design & approvals — our architects draw the scheme while planning or permitted development paperwork, structural calculations and party wall notices progress together.
- Fixed-price contract — every element specified and priced before construction, from foundations to door hardware.
- Groundworks & shell — excavation, foundations, walls, steel and roof, taken to weathertight while you carry on living in the house.
- Fit-out — insulation, services, glazing, kitchen, flooring and decoration, with the opening into the existing house formed once the shell is sealed.
- Completion — building control inspection, snagging, external works and handover with the full certification pack.
Read the full house extension guide for extension types, permitted development limits and the build programme stage by stage.
Many rear extensions can proceed under permitted development — broadly up to 3m deep on attached houses and 4m on detached, extendable to 6m and 8m through the prior approval scheme — but conservation areas, Article 4 directions and listed status change the picture, and every extension needs Building Regulations approval regardless of the planning route. Where foundations come within 3m of a neighbouring building, the Party Wall etc. Act 1996 obliges you to give adjoining owners a minimum of two months’ written notice before construction can begin. Our planning guide library sets out the rules for each borough.
Why Hampstead Renovations
We hold £10 million public liability insurance with Aviva; the certificate is available on request.
House Extensions in West Hampstead: Questions
Which West Hampstead houses suit an extension?
The terraced streets are the sweet spot: Fortune Green Road, Mill Lane and Sumatra Road hold bay-fronted Victorian terraces ideal for rear extensions, lofts and whole-house work, with Edwardian villas mixed through and substantial red-brick mansion blocks between them. If you're in a terrace or villa, the extension conversation is usually a live one.
Do I need planning permission to extend in West Hampstead?
In the protected streets, expect a full application. Conservation areas at Fortune Green, West End Green and Mill Lane cover the area's best Victorian and Edwardian streets, and Camden applies Article 4 controls with real scrutiny of external change — outside those boundaries the position eases, so the first step is simply locating your house on the map.
What site factors are specific to building in West Hampstead?
Two, and they're geographic: the busy West End Lane spine, which complicates loading and access at certain hours, and the three railway lines that cross the area, which fix where traffic and deliveries can flow. Neither stops an extension; both belong in the construction programme from the start.
Can flats or mansion blocks in West Hampstead be extended?
The bar is explicit and high: within the West End Green Conservation Area, Camden's appraisal states that further sub-division or extension of the mansion blocks will normally prove unacceptable. With so much of the area leasehold — freeholder and managing agent involved from the start — flat owners are usually better served by reconfiguring within the existing envelope, which we also do.
How much does a house extension cost in West Hampstead, NW6?
House extensions in West Hampstead typically cost £2,400–£3,800/sqm. A single-storey rear extension runs approximately £45,000–£85,000, while a double-storey extension costs £80,000–£160,000. Our fixed-price contracts include foundations, structural steelwork, full build and interior fit-out.
More Services in West Hampstead
Book a Free Consultation
Visit our studio or invite us to survey your home. We’ll assess scope, discuss design possibilities and provide an honest budget framework — completely free.
Free Consultation
We survey your property, discuss your vision and provide a clear budget framework.