Flat roof extensions for homes in Greater London
If you live in Greater London and want more space without moving, a flat roof extension is one of the most practical ways to get it. We handle the drawings, approvals and the build.
- Guide priceFrom £27,000 inc VAT
- PlanningOften permitted development (3–4 m), or prior approval up to 6–8 m
- Towns covered105
- Site visitFree, no obligation
Towns in Greater London
- Abbey Wood
- Acton
- Barking
- Barnes
- Barnet
- Battersea
- Beckenham
- Becontree
- Bethnal Green
- Bexley
- Blackheath
- Bow
- Brixton
- Brockley
- Camden Town
- Canning Town
- Carshalton
- Catford
- Chalk Farm
- Chelsea
- Chessington
- Chingford
- Chislehurst
- Chiswick
- Coulsdon
- Cricklewood
- Croydon
- Dagenham
- Earlsfield
- East Barnet
- Edmonton
- Eltham
- Enfield
- Enfield Lock
- Feltham
- Finchley
- Friern Barnet
- Fulham
- Golders Green
- Greenford
- Greenwich
- Hampton
- Hanworth
- Harlesden
- Harringay
- Harrow
- Hayes (Hillingdon)
- Heston
- Highbury
- Holloway
- Hook
- Hornchurch
- Hounslow
- Ilford
- Isleworth
- Kilburn
- Leytonstone
- Manor Park
- Mitcham
- Morden
- Muswell Hill
- New Cross
- New Malden
- Norbury
- Northolt
- Notting Hill
- Orpington
- Palmers Green
- Peckham
- Pinner
- Plumstead
- Ponders End
- Purley
- Putney
- Richmond
- Roehampton
- Romford
- Ruislip
- Shepherds Bush
- South Croydon
- South Norwood
- South Ruislip
- Southall
- Stamford Hill
- Stepney
- Stratford
- Streatham
- Surbiton
- Sutton
- Thamesmead
- Tooting
- Tottenham
- Upper Norwood
- Uxbridge
- Wallington
- Walthamstow
- Wealdstone
- Welling
- Wembley
- West Ham
- Willesden
- Wimbledon
- Wood Green
- Woodford Green
- Worcester Park
Extensions in and around Greater London
Towns we cover in Greater London include Bexley, Barking, Sutton, Croydon, Ilford, Enfield, Harrow, Tottenham. London's housing is dominated by Victorian and Edwardian terraces, many with a rear outrigger and a side return, and 1930s semis in the outer boroughs. Conservation areas are common, so the planning check comes first.
Do I need planning permission in Greater London?
In England a single-storey rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.
Homes in conservation areas, national parks, National Landscapes (formerly AONBs), the Broads and World Heritage Sites have tighter rules, so we always check the property's status and planning history before design starts.
Building over or within 3 m of a public sewer needs the water company's consent, usually through a build-over agreement, before the foundations go in.
Building regulations approval is separate from planning. In England you can use the council's building control team or a registered building control approver; a full plans application gets the drawings checked before work starts, and the inspector signs the work off with a completion certificate.
Applications are decided by the local planning authority (your district, borough or unitary council).
What should I budget for a flat roof extension in Greater London?
Labour and material costs vary across the UK, so for Greater London we use our London factor (×1.3). The ranges include VAT and exclude design, structural and council fees.
Typical rates in Greater London: £2,280 to £4,360 per m² including VAT, depending on specification.
| Size | Essential | Standard | Premium |
|---|---|---|---|
| 3 m × 4 m 12 m² | £27,000 – £32,000 | £31,500 – £41,000 | £40,500 – £52,500 |
| 4 m × 5 m 20 m² | £45,500 – £53,500 | £53,000 – £68,000 | £67,500 – £87,500 |
| 5 m × 6 m 30 m² | £68,000 – £80,000 | £79,500 – £101,500 | £101,000 – £131,000 |
Want a range for your exact size? The guide-price tool takes about a minute.
Included in a typical project
- Falls and outlets designed to drain properly
- Parapets or edge trims and flashings to the house
- Warm-roof design with insulation above the deck
- Membrane choice: single-ply, EPDM or GRP
- Lanterns or rooflights with upstands
How the project works
Site visits are free and there is no obligation. Where drawings are needed, the design stage is priced in writing before it starts.
Free site visit
It starts with a visit to your house to measure, check access and talk through ideas and budget.
Design and approvals
We draw the design, agree it with you and handle planning or permitted development checks and building regulations.
Fixed written price
With the design and specification agreed, you get a fixed written price and a start date.
Build and sign-off
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Your questions about a flat roof extension in Greater London
How long does a flat roof extension take to build in Greater London?
On site, typically 10 to 16 weeks once approvals are in place. Before that, allow 4–12 weeks design and approvals.
Do you cover all of Greater London?
Yes, across the whole of Greater London. Site visits are free and there is no obligation.
Do I need building regulations approval in Greater London?
Yes. Almost every extension needs it, whatever the planning route. We prepare the drawings and book the inspections.
Are flat roof extensions cheaper?
Usually slightly, because there is less roof structure and no tiles. Our guide range is about £2,280 to £4,360 per m² including VAT.
Can I walk on a flat roof extension?
Only for maintenance unless it is designed as a terrace. A roof terrace or balcony needs planning permission and a different structure.
Book a free site visit in Greater London
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.