A double-storey extension adds two floors of new space to your house in one build, typically a larger kitchen or living room downstairs with an extra bedroom, bathroom or en-suite above, sharing one set of foundations and one roof.
Homes across London vary a great deal, so we price a double-storey extension only after seeing the property. Our coverage takes in Brent, Islington, Westminster and Bexley and the surrounding districts. As a guide, expect £78,000–£156,000 including VAT in London; the final figure depends on size, materials and access. Any permissions are checked against the rules for England before we quote.
- Guide price
- £78,000–£156,000 inc VAT
- Time on site
- 14–22 weeks on site
- Planning rules
- England
- Price level
- About 30% above the national guide
- Towns listed
- 90
- Survey
- Free, with a written quote
Double-storey extensions prices in London
To help you plan, we show what a double-storey extension typically costs in London instead of holding figures back for a sales call. The range is £78,000–£156,000 with VAT, using rates in London that are about 30% above the national guide. A free survey then fixes your actual price.
| Type of job | What it usually involves | Guide in London |
|---|---|---|
| Small (15–20m² total) | A compact rear or side extension adding a small room on each floor. | £52,000–£84,000 |
| Typical (30–40m² total) | A larger kitchen or living room below with a double bedroom or en-suite above. | £78,000–£156,000 |
| Large (50m² plus total) | Wide or deep extensions, often with a new bathroom, steelwork and high-spec glazing. | £130,000–£234,000 |
The main things that change the figure:
- Combined floor area across both storeys
- Bathrooms, en-suites and plumbing on the upper floor
- Foundation depth, ground conditions and drains to divert
- Scaffolding duration, access and the level of finishes
Scope of the work
- Groundworks, foundations and below-ground drainage
- First-floor joists, stud walls and new openings upstairs
- Roof structure tied into the existing roof, tiled to match
- Scaffolding for the full build, erected and inspected
- Windows, external doors, plastering and internal doors
- Building control inspections and completion certificate
Housing across London
London's housing is dominated by Victorian and Edwardian terraces, often in yellow London stock brick, with Georgian terraces in central districts and mansion blocks across many inner areas. Outer boroughs have large belts of interwar semis, and there are extensive post-war council estates. Many houses have been split into flats, and conservation areas are widespread.
Terraces suit side-return extensions and rear dormer loft conversions; interwar semis commonly take hip-to-gable lofts. Shared party walls, restricted parking and conservation rules often shape the plans and the programme.
London Clay shrinks and swells with the seasons, and street trees close to houses can contribute to movement, which affects foundation design.
Do you need permission in London?
For anyone in London, the relevant framework is England's. The summary below is general, so we always contact the council about your address before putting a price in writing.
In England, a two-storey rear extension can only be permitted development if it is no more than 3 m deep, at least 7 m from the rear boundary and finished to match the house. Most double-storey and all two-storey side extensions need full planning permission.
Building Regulations approval is needed, with structural calculations for beams, foundations and the roof. The Party Wall etc. Act 1996 often applies on semi-detached and terraced houses.
Rules change and every property is different, so we check the planning history and constraints for your address before we quote.
How does the job run?
A visit to your home
We begin by looking at the job in person. During the free survey we discuss options, materials and budget for a double-storey extension, and photograph or measure anything the quote needs to reflect.
Price and scope agreed
We put everything into a written, fixed-price quote: the specification, what's excluded, staged payments and the expected time on site. Take whatever time you need to decide; there's no pressure to commit.
Dates and permissions
Preparation matters as much as the build. We agree access, parking and working hours with you, order materials in good time, and confirm any permissions so the job isn't held up once it starts.
Finish and handover
Work goes ahead as scheduled and you deal with one contact throughout. When the last trade leaves, we clear and clean the site, talk you through what has been done and pass on any certificates and care instructions.
How we work
Frequently asked questions
Will the extension affect my neighbours?
A double-storey extension can affect neighbours' light, outlook and privacy, which is why planning departments look closely at height, depth and window positions. Side windows facing neighbours often need obscure glass. Work near a shared wall may also need party wall notices; the Party Wall etc. Act 1996 applies in England and Wales only. We talk through these points early so the design is realistic.
Which postcodes in London do you cover?
We cover HA0, EC1, SW1 and DA5, along with the rest of London. If your postcode is not listed, get in touch anyway: our coverage is UK-wide, and we can usually arrange a survey wherever you live. Enter your postcode in the guide-price tool or contact form and we will confirm.
Do I need planning permission in London?
It depends on the work, the size of the project, your property type and whether the building is listed or in a conservation area. London is in England, so England's rules apply. Many smaller jobs need no planning application, but some still need building control approval. We check what applies to your address before quoting.
Can we live at home while it is built?
Most families stay at home during a double-storey extension. The new structure is built outside first, and we only break through into the existing rooms near the end, usually one floor at a time. Upstairs, this may mean a bedroom is out of use for a week or two. We fit dust screens, protect floors and stairs, and plan any time without water or power in advance.
How much does a double-storey extension cost?
A typical double-storey extension of 30–40m² across both floors costs £78,000–£156,000, built to a plastered finish. As a rough guide, allow around £1,400–£2,600 per square metre plus fixed costs for groundworks, scaffolding and fees. The second storey usually costs less per square metre than the first, because foundations and roof are shared. Bathrooms upstairs and a complex roof add most. We confirm a fixed price after the survey.
Towns in London
Choose your town from the list to see how we price and plan a double-storey extension in your part of London, including typical time on site.
- Acton
- Archway
- Barking
- Barnes
- Barnet
- Battersea
- Beckenham
- Becontree
- Bexley
- Blackheath
- Blackwall
- Bow
- Brent
- Brixton
- Camden Town
- Canary Wharf
- Canning Town
- Carshalton
- Catford
- Chalk Farm
- Chelsea
- Chessington
- Chingford
- Chiswick
- Coulsdon
- Cricklewood
- Croydon
- Dagenham
- East Barnet
- Edmonton
- Eltham
- Enfield Town
- Feltham
- Finchley
- Fulham
- Golders Green
- Greenford
- Greenwich
- Hadley Wood
- Hampton
- Hanworth
- Harrow
- Hayes
- Heston
- Highbury
- Holloway
- Hook
- Hornchurch
- Hounslow
- Ilford
- Isleworth
- Islington
- Kilburn
- Leytonstone
- Mitcham
- Morden
- Muswell Hill
- New Malden
- Northolt
- Notting Hill
- Peckham
- Pimlico
- Pinner
- Purley
- Putney
- Richmond
- Romford
- Ruislip
- Shepherds Bush
- Soho
- South Croydon
- Southall
- Stamford Hill
- Stratford
- Streatham
- Surbiton
- Sutton
- Thamesmead
- Tottenham
- Uxbridge
- Wallington
- Walthamstow
- Wealdstone
- Welling
- Wembley
- Westminster
- Willesden
- Wimbledon
- Wood Green
- Woodford Green