Extension builders in the UK
Single and double storey extensions, side returns and wrap-arounds.
- Towns and cities
- 56
- Single storey, per m² from
- £1,800
- Accreditations explained
- 3
- Single storey, per m²
- £1,800 – £2,500shell to finished
- Typical single storey
- £40,000 – £55,000around 20 m²
- Double storey
- £55,000 – £90,000around 30 m² over two floors
- Side return
- £45,000 – £75,000London terrace, typical
Typical UK ranges for 2026, excluding VAT. Local figures on each city page are adjusted for regional labour rates.
Extension builders by town and city
56 towns and cities, each listing up to 10 firms from Google's results for that town, ranked on Google rating, online presence and other factors.
Launch cities
- Extension builders in LondonGreater London
- Extension builders in BirminghamWest Midlands
- Extension builders in ManchesterGreater Manchester
- Extension builders in LeedsWest Yorkshire
- Extension builders in BristolBristol
- Extension builders in LiverpoolMerseyside
- Extension builders in SheffieldSouth Yorkshire
- Extension builders in NottinghamNottinghamshire
- Extension builders in CoventryWest Midlands
- Extension builders in LeicesterLeicestershire
- Extension builders in DerbyDerbyshire
- Extension builders in SouthamptonHampshire
- Extension builders in CroydonGreater London
Everywhere else
- EdinburghCity of Edinburgh
- GlasgowGlasgow City
- CardiffCardiff
- AberdeenAberdeen City
- YorkNorth Yorkshire
- NorthamptonNorthamptonshire
- NorwichNorfolk
- OxfordOxfordshire
- PlymouthDevon
- BrightonEast Sussex
- BelfastCounty Antrim
- NewcastleTyne and Wear
- WolverhamptonWest Midlands
- CambridgeCambridgeshire
- Stoke-on-TrentStaffordshire
- Milton KeynesBuckinghamshire
- BlackpoolLancashire
- BathSomerset
- SwindonWiltshire
- ColchesterEssex
- DoncasterSouth Yorkshire
- CheltenhamGloucestershire
- ExeterDevon
- GloucesterGloucestershire
- SwanseaSwansea
- St AlbansHertfordshire
- PortsmouthHampshire
- BromleyGreater London
- EnfieldGreater London
- HarrowGreater London
- RomfordGreater London
- EalingGreater London
- BarnetGreater London
- RichmondGreater London
- North LondonGreater London
- East LondonGreater London
- South LondonGreater London
- West LondonGreater London
- FulhamGreater London
- WimbledonGreater London
- WandsworthGreater London
- ChiswickGreater London
- ClaphamGreater London
What the badges actually mean
The accreditations that matter for extension builders, in plain English.
Federation of Master Builders
Independently inspected and vetted before joining.
TrustMark registered
The only government-endorsed quality scheme for work in and around the home. Covers trading standards as well as technical competence.
CHAS accredited
Health and safety pre-qualification. Matters most on structural work and anything involving scaffolding.
Before you get quotes
Work out the budget and the paperwork first. It changes the conversation you have with the firm.
House extension cost per square metre in 2026
Per-square-metre prices for single-storey, two-storey, side return and kitchen extensions, costs by size, the fees outside the build price, and planning limits by nation.
Permitted development: what you can build without planning permission
The permitted development limits for extensions, lofts, porches and outbuildings in England, where the rights do not apply, what prior approval and a certificate cost, and how Wales, Scotland and NI differ.
Party wall agreements: when you need one and what it costs
When the Party Wall Act applies, which notice to serve and how far ahead, what your neighbour can do, what a surveyor's award costs, and the rules in Scotland and NI.
Do I need planning permission? A decision guide
Which home projects need planning permission in England and which do not, the homes where the answer changes, what a definite answer costs, and how Wales, Scotland and Northern Ireland differ.
Side return extensions on a Victorian terrace: cost, rules and build
What a side return extension costs in 2026, when it needs planning permission in each UK nation, the party wall notices it triggers, and how the glazing rules shape the roof.
Orangery or conservatory: which is which, and does it matter?
What separates an orangery from a conservatory, what each costs in 2026, when building regulations treat either room as an extension, and the planning rules across the UK.
Extension builders: common questions
How far can I extend without planning permission?
Under permitted development, three metres for a terrace or semi and four for a detached, doubled to six and eight under the prior approval process. Height, materials and how much garden you cover all carry separate limits, and none of it applies in a conservation area.
Do I need a party wall agreement?
If you are excavating within three metres of a neighbour's foundations or building on the boundary, yes. You must serve notice two months before work starts. Skipping it is the most common reason extension projects stall.