Home Extension Design in Hammersmith and Fulham: Planning, Costs and What's Realistic in 2026
A home extension in Hammersmith and Fulham typically costs £4,000 to £5,500+ per m² to build in 2026, at mid-range specification, before VAT and professional fees. Planning here is less forgiving than in most of London: the borough has 44 conservation areas covering about half its streets, and a borough-wide Article 4 Direction means every basement project needs full planning permission. This page covers what the council allows, what it costs, and how to find out where your street stands before design work starts.
Studio MASS is a residential design practice led by an architectural technologist. We design and deliver extensions, loft conversions and refurbishments across London, from first feasibility check to completed build.
Do you need planning permission for an extension in Hammersmith and Fulham?
Roughly half the borough sits inside a conservation area, so the honest answer is: check your street first. Outside conservation areas, a single-storey rear extension up to 3 metres beyond the original rear wall (4 metres on a detached house) usually falls under permitted development, as do most loft conversions within volume limits. Inside one of Hammersmith and Fulham's 44 conservation areas, side extensions and rear extensions beyond 3 metres need planning permission, as does any rear extension of more than one storey.
Basements are the borough's firmest rule. A borough-wide Article 4 Direction, made on 25 April 2017 and in force since 26 April 2018, removed permitted development rights for basement development across the whole borough. Full planning permission is required for any new basement or basement extension, judged against Policy DC11 of the Local Plan, and every application must include a Construction Method Statement.
Many individual properties, especially in conservation areas, are also covered by property-specific Article 4 Directions that remove rights for smaller alterations, so even replacement windows can need planning permission. The council publishes a list of affected properties, and checking your address against it is part of our Stage Zero review, before any design work starts.
What kinds of homes get extended in Hammersmith and Fulham?
Victorian and Edwardian terraces dominate the borough, and they are the houses we are asked about most: side-return kitchen extensions, loft conversions and whole-house refurbishments. In Brackenbury Village, protected within the Bradmore Conservation Area, the streets of terraced houses and cottages were largely complete by 1890, and the council's character profile expects alterations to respect that consistency.
Parsons Green and Brook Green each have their own conservation area, with larger Victorian family houses arranged around their greens. Fulham's grid of terraced streets is similarly layered with designations, from Central Fulham to Moore Park, Bishops Park and Hurlingham, while estates such as Queen's Club Gardens show the borough's mansion-block side, where flat owners face a different consent route entirely. The common thread: period fabric, tight plots and a council that takes character seriously. Good design here works with that, not against it.
How much does a home extension cost in Hammersmith and Fulham in 2026?
Hammersmith and Fulham sits in London's inner, higher-price construction zone. From our 2026 Extension Cost Guide, built from BCIS indices, FMB build cost data and our own completed projects:
A single-storey extension in Hammersmith and Fulham costs £4,000 to £5,500+ per m² at mid specification in 2026. A loft conversion runs £3,200 to £3,800 per m². Conservation area projects carry roughly 15% on top for material restrictions and period-appropriate detailing. These figures are construction only; VAT at 20% and professional fees are additional.
Before a brick is laid, expect £8,000 to £16,000 in professional and statutory fees on a typical project, including the £548 planning application fee that applies from April 2026.
The full breakdown by extension type and specification level is in our free Extension Cost Guide 2026, no email required.
For a sense of how we work on period terraces like these, see the Rathcoole Gardens project page, a side-return kitchen extension to a Victorian terrace in Hornsey, north London, and the Drakefield House project page, both completed London projects with the design decisions explained.
Who designs your extension if not an architect?
An architectural technologist designs buildings with a focus on how they are built: construction detail, building regulations, and buildability, alongside layout and light. In the UK "architect" is a legally protected title, so we don't use it. What matters for a Hammersmith and Fulham extension is the same either way: design within the local planning context, technical drawings a builder can price accurately, and someone accountable from first idea to finished build. That is what we do, through one team and five stages, starting with a Stage Zero review that tells you what is realistic for your budget and what planning will allow before design begins.
Start with a conversation
The best starting point is our short questionnaire. It takes a few minutes and tells us about your home, your brief and your budget. We review it and arrange a free thirty-minute call, with an honest view on feasibility either way.
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