House Extensions Hammersmith
Single storey rear and double storey extensions in Hammersmith, planning, structure and build under one contract.
- Rated 4.9 from 31 reviews on MyBuilder
- Single-storey rear extension from £40,000
- Free site survey, itemised quote
GS Renovation builds extensions throughout Hammersmith, tailored to the bay-fronted Victorian and Edwardian terraces that fill the W6 streets between the River Thames and Goldhawk Road. We handle foundations, steelwork, roofing and full fit-out to add usable space to these period terraced homes.
In Hammersmith, a single-storey rear extension typically starts from £40,000, or £2,000 to £2,800 per m² (indicative London ranges, Architecture for London, Resi, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Hammersmith: the structural engineer we appoint designs the structure, we build it, and building control signs it off.
Price guide
| Work | Indicative London range |
|---|---|
| Single-storey rear extension | from £40,000 |
| Rear extension, per m² | £2,000 to £2,800 |
| Side return, per m² | £2,400 to £3,200 |
| Wraparound, per m² | £2,400 to £3,200 |
| Double storey, per m² | £1,800 to £2,600 |
| Basement extension | see the basement page |
Indicative London ranges (Architecture for London, Resi, MyBuilder and Checkatrade, 2026), not a quotation. Prices checked September 2026. Full breakdown: Extension Costs & Planning.
Quick estimate for Hammersmith
Hammersmith range: choose above
Side-return and rear extensions in Hammersmith
The classic project on a Hammersmith terrace fills in the side return alongside the rear closet wing, widening a narrow galley kitchen into a bright open-plan space that runs the full width of the house. On tighter W6 plots we often combine the side return with a modest rear extension, then knock through into the middle reception room with a steel beam to create a single kitchen-diner opening onto the garden.
We start with proper foundations and groundworks, allowing for the shallow footings and drain runs common on these older terraces, then build the walls, install the steel and form the roof. Rooflights and glazed rear doors bring light deep into the plan, which matters in period houses where the middle of the terrace can otherwise feel dark.
Housing in Hammersmith
The valuation list shows roughly 15,040 homes in Hammersmith, of which 56% are pre-1919, 9% interwar and 34% post-1945, split 77% flats to 23% houses. Since most homes here are flats, a flat in Hammersmith has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent.
Flood risk and the 100 square metre line in Hammersmith
A flood risk assessment has to go with a planning application for a property in a flood risk zone, and two thirds of Hammersmith and Fulham lies within one. Homes near the river around Furnivall Gardens and the Riverside Studios are the obvious case, but the zone runs well beyond the riverside streets. For a Hammersmith extension that needs planning permission, find out early whether the address is in the zone. If it is, the assessment is commissioned alongside the drawings, and it can influence floor levels and the choice of materials at ground level.
Size sets two more thresholds. New floorspace of 100m2 or more, or a new dwelling, makes a development liable for the Community Infrastructure Levy. In a conservation area, 100 square metres of new floor space is also the point at which a design and access statement becomes necessary. A single storey rear or side return extension on a terrace is nowhere near that size. A larger scheme, or one that adds a flat, can cross one of these lines, so the floor area and the number of homes are settled at design stage rather than left to the application form.
Planning and party walls in Hammersmith and Fulham
Some extensions in W6 fall under permitted development, but many do not, so the route depends on your specific property. If your home sits in a conservation area, has been previously extended, or you want a larger footprint, you will usually need a full planning application to Hammersmith and Fulham Council rather than relying on permitted development rights.
Either way, the structural work is covered by building regulations and inspected by building control, which is separate from planning. Because these terraces share party walls with both neighbours, most extensions also trigger Party Wall Act notices for excavation near the boundary or for cutting into the shared wall. We guide you through all three strands so the project starts on solid legal footing.
Kitchen extensions in Hammersmith
77% of homes in Hammersmith are flats, and a flat has no householder permitted development, so a ground-floor flat's kitchen extension needs planning permission from Hammersmith and Fulham Council and the freeholder's consent. Most kitchen extensions here are on the 23% of homes that are houses. The fit-out is priced on its own page, kitchen renovation in Hammersmith; the build figures are in the table above.
Double storey extensions in Hammersmith
Under permitted development a two-storey rear extension can go no more than 3 metres beyond the original rear wall and must stay at least 7 metres from the rear boundary, and in a conservation area it is not permitted development at all. Many gardens are too short for the 7 metre rule, so a double storey extension in Hammersmith often needs planning permission from Hammersmith and Fulham Council. It is a job for the 23% of homes that are houses; a flat cannot add a storey this way. Article 4 Directions restricting some permitted development rights have been made on some properties in Hammersmith Grove since the Hammersmith Grove Conservation Area character profile was published (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- Full fit-out, finishing and making good
- Planning applications and permitted development assessments
- Brickwork and mortar matched to the existing elevation
VOA Council Tax stock of properties, March 2025, for Hammersmith Broadway, Brook Green, Ravenscourt Park North and Ravenscourt Park South. Counts rounded by the VOA.
The GS Renovation Difference in Hammersmith
Hammersmith homeowners choose GS Renovation because one team manages the extension from foundations to final decoration, including the steelwork, roofing and services. We know the W6 terraced stock, we advise honestly on whether you need planning permission or permitted development, and we plan the programme around the party wall notices you serve when building tight against neighbours, all backed by our founder's 30+ years of work.
- Drainage diverted or built over with the right approval in place
- Materials priced at options, so you choose the finish
- Brick and mortar matched to the existing elevation
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
It's the second time I have hired George and he has been absolutely professional and the work he did resembles perfectly what I had in mind. Being an…
FAQ
Frequently Asked Questions about House Extensions Hammersmith
How do you price house extensions in Hammersmith?
Pricing house extensions for a Hammersmith property starts with a W6 survey and ends with a written figure inside £2,000 to £2,800 per m² for a rear extension (indicative). The key physical check comes first: the drainage run under the footprint decides the foundations. The quotation then splits into structure, services and finishes, with a Hammersmith and Fulham Council building control inspection of the foundations before concrete is poured shown separately.
Will my Hammersmith side-return extension need planning permission?
Many side-return and rear extensions in W6 qualify as permitted development, but conservation area status, previous extensions or a larger footprint often require a full planning application to Hammersmith and Fulham Council. We assess your specific terrace early, advise on the likely route, and handle the building regulations whichever way the planning falls.
Can I extend a ground-floor Hammersmith flat into the garden?
Possibly, but not under permitted development, which applies to houses rather than flats. That means a full planning application to Hammersmith and Fulham Council, plus the freeholder's consent, since the lease usually controls the garden, walls and any structural change. Building regulations apply regardless. With 77% of Hammersmith homes being flats, this is the normal route here.
What happens to drains running beside a Hammersmith side return?
They often sit exactly where the extension will go, so they are surveyed first. Private drains can usually be rerouted with a proper fall under Part H and new access points outside the footprint. Where a public sewer lies under or near the site, the water company must consent before building over it. That can take time, so it is checked before design is fixed.
Will a Hammersmith extension make the middle room dark?
It can in a terraced house, where filling the side return takes away the middle room's only window. Rooflights or a glazed strip along the junction with the house bring daylight back into the centre of the plan, and a lantern over the kitchen does the rest. Part L sets insulation standards, so glazed areas are balanced against the rest of the extension, and building control reviews the roof design.
Can new foundations sit next to the old footings of a Hammersmith Victorian house?
Yes, but the engineer designs the junction carefully. Victorian footings are often shallow brick steps, while a new extension needs deeper concrete. Digging below old footings can undermine them, so the engineer may specify a gap, a different foundation type or local underpinning. Where digging is within 3 metres of a neighbour below their foundations, a month's notice applies.
Can a Hammersmith extension include a basement underneath it?
Only with full planning permission, which is needed to create any new basement. Local Plan policy stops a basement reaching under the garden for more than 50% of the garden's depth. The application also needs a Construction Method Statement. An extension with a basement below it is therefore a much larger planning case than the extension alone, and the two are designed together.
What if a tree stands close to a Hammersmith extension in a conservation area?
Allow six weeks before touching it. In a conservation area the council needs six weeks' notice before work on any tree whose trunk measures 75mm or more across. That covers removing or cutting back a tree in the way of the footprint. The notice is best sent with the planning drawings, and the structural engineer designs the foundations for the tree that will remain.
Does a Hammersmith extension on a Building Notice still need structural calculations?
Yes. An extension on a Building Notice still has to have structural calculations submitted, covering every part of the structural work. The notice route saves no design work, and Hammersmith and Fulham Council recommends it only for very small works. An extension with foundations, steel and a new roof is better approved on drawings before the ground is opened.
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