House Extension Hammersmith & Fulham: Costs, Planning and Vetted Builders
Side return, rear, wraparound and double-storey extensions across Hammersmith, Fulham, Shepherd’s Bush and Barons Court. Costs from £32,000, planning rules explained, and up to 3 matched quotes from vetted local builders. Free, with no cold calls.
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Walk down almost any residential street in Fulham or Hammersmith, and you’ll see the same thing over the back walls: glass roofs, steel-framed doors and kitchens that now reach most of the way down the garden. Extending is how families here make a Victorian or Edwardian terrace work for modern life without leaving the area they love.
The most common project is the side return extension, which fills the narrow strip beside the kitchen. Close behind is the wraparound, which combines a side return with a rear extension to create one large kitchen, dining and living space.
Hammersmith & Fulham has two rules that catch people out. First, the council has a borough-wide Article 4 Direction, in force since April 2018, so any basement excavation needs planning permission. Second, much of the borough, especially Fulham and the Hammersmith riverside, sits in the Thames flood zone, which affects what you need to send with a planning application.
This guide covers house extension costs in Hammersmith and Fulham, the extension types that suit local homes, Permitted Development and planning, conservation areas, flood risk, Party Wall notices, timings and how to find a vetted builder.
House extension costs in Hammersmith and Fulham
House extension costs in Hammersmith and Fulham range from around £32,000 for a modest single-storey rear extension to £250,000 or more for a basement or lower-ground extension. What you pay depends mainly on the type of extension, the floor area, the specification of the glazing and kitchen, and how much structural work is needed.
Building costs here sit above the London average. Labour is in high demand, parking and skip licences cost more, and many streets have narrow access, so materials often have to come through the house. Parsons Green, Hurlingham and Brook Green, where specifications tend to be higher, usually run another 10-20% above the borough figures. Shepherd’s Bush and White City (W12) are closer to the London average.
| Extension type | Typical cost (Hammersmith & Fulham) | Parsons Green, Hurlingham & Brook Green |
|---|---|---|
| Single-storey rear (3m) | £32,000-£55,000 | Add 10-20% |
| Single-storey rear (4-6m) | £50,000-£90,000 | Add 10-20% |
| Side return infill | £40,000-£72,000 | Add 10-20% |
| Wraparound (rear + side return) | £70,000-£145,000+ | Add 10-20% |
| Double-storey rear | £75,000-£155,000+ | Add 10-20% |
| Basement or lower-ground extension | £100,000-£250,000+ | Add 10-20% |
These figures cover foundations, structure, insulation, the roof, external walls, plastering, the floor screed, and first-fix electrics and plumbing. A new kitchen, steel or aluminium glazing and bifold or sliding doors are often priced separately, so check what each quote includes.
Allow another £6,000-£15,000 for professional fees: an architect or designer, a structural engineer, Party Wall surveyors, Building Regulations and, where needed, a flood risk assessment.
Which extension suits your Hammersmith or Fulham home?
The right extension depends on the house, the garden and the street. These are the five types our builders are asked about most in the borough.
Side return extension
Most terraces in Fulham, Hammersmith and Shepherd’s Bush have a side return: a passage, often around 1m wide, that runs beside the kitchen in the rear outrigger. Building over it widens a narrow galley kitchen into a proper room. A glazed or lantern roof over the infill brings light into what is often the darkest part of the house.
Single-storey rear extension
A rear extension pushes the back of the house further into the garden. It suits homes where the side return has already been filled, or where you want a garden room or a bigger dining space. Under Permitted Development, a terrace or semi-detached house can go 3m deep without an application, or up to 6m through the prior approval route described below.
Wraparound extension
A wraparound combines a side return infill and a rear extension into one L-shaped space, usually 25-40m². It creates the largest open-plan kitchen-diner a terrace can have and is the most requested extension in Fulham and Brook Green. Because it must meet the rear and side Permitted Development limits at the same time, many wraparounds need planning permission.
Double-storey rear extension
Building out on two floors adds a bigger kitchen downstairs and an extra bedroom or bathroom upstairs. It’s more common on the larger semi-detached and end-of-terrace houses around Ravenscourt Park and Stamford Brook. A two-storey extension up to 3m deep can be Permitted Development if it is at least 7m from the rear boundary, which rules it out on many shorter terrace gardens.
Basement or lower-ground extension
Some taller houses, particularly in Barons Court, West Kensington and around Hammersmith Grove, have a lower-ground floor. Extending at that level, or digging a new basement, can add a lot of space. In Hammersmith & Fulham, it always needs planning permission because of the borough-wide basement Article 4 Direction. It also needs a flood risk assessment wherever the house is, plus structural, drainage and Party Wall planning from the start.
Permitted Development and planning permission in Hammersmith & Fulham
Many single-storey extensions in the borough can be built without a full planning application. Whether yours can depends on the type of house, its size, its location and whether Permitted Development rights have been removed.
Usually Permitted Development (no application needed)
– Single-storey rear extension up to 3m deep (terrace or semi) or 4m (detached), measured from the original rear wall
– Side return infill up to 4m high and no wider than half the width of the original house
– Double-storey rear extension up to 3m deep, at least 7m from the rear boundary
– Eaves no higher than 3m within 2m of a boundary
– Materials similar in appearance to the existing house
Prior approval for larger rear extensions
A terrace or semi can extend 3-6m to the rear (detached houses 4-8m) through the prior approval route, also called the neighbour consultation scheme. You send drawings to Hammersmith & Fulham Council; your adjoining neighbours get 21 days to comment, and the council has 42 days to decide. If a neighbour objects, the council considers only the effect on their amenity.
When you need planning permission
– Any basement or lower-ground excavation, anywhere in the borough (borough-wide Article 4 Direction since April 2018)
– Extensions beyond the Permitted Development or prior approval limits
– Many wraparounds, where the combined extension exceeds the rear and side limits
– Properties where an Article 4 Direction has removed extension rights; the council publishes a list of properties affected
– Flats and maisonettes, which have no householder Permitted Development rights
– Any work to a listed building, which also needs Listed Building Consent
If you build under Permitted Development, apply for a Lawful Development Certificate. It confirms the extension is lawful and avoids questions from buyers’ solicitors when you sell.
Building Regulations
Every extension needs Building Regulations approval, whether or not it needs planning permission. Building Control checks the foundations, steelwork, insulation, drainage, ventilation and fire safety. Budget £900-£1,600 for Building Regulations fees.
Conservation areas and flood risk in Hammersmith & Fulham
Conservation Areas
Hammersmith & Fulham has 44 conservation areas, including Parsons Green, Walham Green, Hurlingham, Barons Court, Hammersmith Grove, Moore Park, Olympia and Avonmore, The Mall and Shepherds Bush. Rear extensions in a conservation area can still be Permitted Development, but side extensions and anything visible from the street are more tightly controlled. Some individual properties have had their extension rights removed by an Article 4 Direction.
The council also expects materials to suit the house: London stock or red brick to match, lime mortar on older walls, and glazing that doesn’t dominate the original building. If you’re unsure, a pre-application enquiry with the council’s planning team is worth the wait before you commission full drawings.
Flood Risk
Large parts of the borough, especially along the river from Hammersmith through Fulham to Sands End, are in the Thames flood zone. These areas are protected by the river walls and the Thames Barrier, but if your extension needs planning permission and your home is in Flood Zone 2 or 3, you’ll need to send a flood risk assessment with the application. Basements need one wherever they are. Your designer will normally arrange this, and on a straightforward householder scheme it’s a modest cost.
Nearly every extension on a terrace involves a party wall. Under the Party Wall etc. Act 1996, you must serve notice on the affected neighbours before work starts:
– 2 months’ notice for work to an existing party wall, such as cutting in a steel beam or raising the wall
– 1 month’s notice for a new wall built on the boundary line
– 1 month’s notice for excavation within 3m of a neighbour’s foundations (or 6m in some deeper cases), which covers most extension foundations on a terrace
If your neighbour agrees in writing within 14 days, you can go ahead. If they dissent or don’t reply, surveyors prepare a party wall award. Budget £900-£1,800 per neighbour where an award is needed, and more for basements. Talking to neighbours before the formal notice lands makes a big difference, and on streets where extensions are common, most agree.
Extending in each part of the borough
Fulham and Parsons Green (SW6)
Fulham’s long streets of Victorian and Edwardian terraces are ideal for side return and wraparound extensions. Around Parsons Green, Hurlingham and the Peterborough Estate, clients often want a high specification: slim steel-framed glazing, a large roof lantern and a bespoke kitchen. Parts of Fulham near the river are in the flood zone, so check early if your scheme will need planning permission.
Hammersmith, Brook Green and Ravenscourt Park (W6)
W6 mixes Victorian terraces, larger semi-detached houses and some double-fronted homes. Brook Green and Ravenscourt Park attract larger wraparound and double-storey projects. Many streets are in conservation areas, so side extensions and anything visible from the road need careful design.
Shepherd's Bush and White City (W12)
W12 has a lot of smaller Victorian terraces, where a side return infill is the most cost-effective upgrade. Costs here are closer to the London average, and Permitted Development or prior approval often covers the work.
Barons Court and West Kensington (W14)
W14 has more mansion blocks and converted houses. Flats have no householder Permitted Development rights, so extensions to flats need planning permission and the freeholder’s consent. Whole houses in Barons Court are often tall, with lower-ground floors, which opens up a lower-ground extension, subject to planning.
How long does a house extension take in Hammersmith and Fulham?
– Side return infill: 8-12 weeks on site, or 4-6 months in total including design, Party Wall notice and Building Regulations
– Single-storey rear (Permitted Development): 10-16 weeks on site, or 4-6 months in total
– Single-storey rear (prior approval): add about 6-8 weeks before work starts, for 5-7 months in total
– Wraparound: 12-20 weeks on site, or 6-9 months in total, plus 8-13 weeks if planning permission is needed
– Double-storey rear: 14-22 weeks on site, or 7-10 months in total
– Basement or lower-ground extension: 24-40 weeks on site, or 12-18 months from first instruction, including planning
Steel-framed glazing and roof lanterns can take 8-12 weeks to make, so your builder should order them early.
How to pay for your extension
Every QuoteMyRenovation builder agrees to milestone payments. You pay a deposit of around 10%, then in stages as each part of the job is finished: foundations approved by Building Control, walls to roof level, roof on and watertight, first fix, and plastering and second fix. A 5% retention is held back until any snags are fixed. We check in with you before each payment. See how milestone payments
How to find a vetted house extension builder in Hammersmith and Fulham
An extension on a terrace street is a logistics job as much as a building one. Builders need a parking suspension and skip licence from the council; they often have to bring materials through the house, and they need to keep the neighbours on side. When you compare quotes, ask each builder:
– Have you built side return or wraparound extensions in SW6, W6 or W12, and can I see one?
– Who arranges parking suspensions, the skip licence and deliveries?
– Is the Party Wall surveyor included, or is it a separate cost?
– What is included for glazing, roof lights and doors, and what are their lead times?
– Will you provide a programme of works with milestone payment dates?
– Who will run the site day-to-day?
QuoteMyRenovation matches Hammersmith and Fulham homeowners with vetted local extension builders who read your brief before deciding to quote. You get up to 3 matched quotes from builders who know what you need, with no cold calls. It’s free to use.
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COMMON QUESTIONS
Frequently Asked Questions About House Extension Hammersmith
Questions homeowners ask us most often before submitting their brief.
How much does a house extension cost in Hammersmith and Fulham?
Do I need planning permission for a side return extension in Fulham?
What are the Permitted Development limits for a rear extension?
Can I dig a basement in Hammersmith and Fulham?
Does flood risk affect my extension in Fulham or Hammersmith?
Do I need a Party Wall agreement for an extension in a terrace?
How long does a house extension take in Hammersmith?
How should I pay for a house extension?
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