About this page: Home Extensions London is a free enquiry service run by Web Designer Limited (trading as Zoib). We pass enquiries to independent extension builders and design-and-build firms; we don’t carry out the work, and we can’t guarantee that every enquiry is taken up. Figures below are quoted from the named sources with their dates; they are not our prices. More about this site.
The published figures
We don’t publish our own prices: we aren’t builders. The figures below come from the named cost guides, as they read on 20 October 2026.
| What | Published figure | Source |
|---|---|---|
| Standard, medium-sized kitchen extension | Average about £30,000 | Checkatrade kitchen extension guide (updated April 2026) |
| Kitchen extension compared with a plain room extension | Expect about £15,000 to £35,000 more, because of plumbing, gas, electrics and kitchen fitting | Checkatrade kitchen extension guide |
| Bi-fold doors on a kitchen extension | Add around £5,000 for materials and installation | Checkatrade kitchen extension guide |
| Full extension, per m² (UK) | About £1,800 to £3,000 per m² | Checkatrade house extension guide |
| Single-storey extension in London, per m² | About £2,300 to £3,400 per m² | HomeOwners Alliance extension costs |
The guides are honest that these are ballparks. Checkatrade’s own FAQ answers “Is £40k enough for a kitchen extension?” with “No” for a typical kitchen extension, because of the plumbing, electrics, gas and kitchen fitting involved.
A worked illustration, not a quote: applying the HomeOwners Alliance London band of £2,300 to £3,400 per m² to a 20 m² single-storey extension gives roughly £46,000 to £68,000 for the building, before VAT and before the kitchen itself. A long, glazed side-return or wraparound with steelwork and a large rooflight can go higher.
Why London sits higher
Both Checkatrade and HomeOwners Alliance say London and the South East usually cost more, mainly because of labour rates. On London streets you can add practical reasons too: restricted access through the house, skips and scaffolding that need licences on the highway, more neighbours to serve Party Wall notices on, and conservation areas or Article 4 directions that affect materials. Our page on extension rules in London covers the consent side.
What a quote usually includes
Checkatrade lists what most kitchen extension quotes cover: foundations and structural work; walls, roofing and insulation; windows and doors; plumbing and electrics; plastering and decorating; basic flooring; kitchen installation (units and worktops may be separate); and waste disposal. Ask each builder to confirm, line by line, which of those they have priced.
Costs people often miss
- Fees and approvals: architectural drawings, structural engineer, planning or prior approval fees (the Planning Portal schedule lists £548 for a householder application and £249 for larger-home-extension prior approval in England from 1 April 2026), Building Regulations charges and Party Wall surveyors.
- The kitchen itself: units, worktops, appliances, tiles and finishes, if they are not in the builder’s price.
- Living through it: a temporary kitchen, extra cleaning, and possibly time away during the noisiest stages.
- Upgrades: underfloor heating, larger glazing, rooflights and lighting design.
- VAT at 20% if the quote is shown without it.
Ways to keep the cost under control
- Fix the design and specification before you ask for prices, so that every builder quotes the same job.
- Keep the plan simple: rectangular footprints and fewer structural openings are usually cheaper to build.
- Work with your existing drainage, gas and electrics where you can; moving the sink or soil stack has knock-on costs.
- Keep a contingency for surprises once walls and floors are opened up. Checkatrade’s loft conversion guide, for example, suggests 10–15% on top of the quote for loft projects.
- Read our page on choosing an extension builder before you sign.
Our sister site extensionprice.com (run by the same company) has a longer London extension cost guide covering single-storey, double-storey and wraparound ranges.
Questions people ask
How much does a kitchen extension cost in London?
Neither Checkatrade nor HomeOwners Alliance publishes a London-only kitchen extension price. Checkatrade gives about £30,000 as a UK average for a medium-sized kitchen extension and says London prices sit at the top end. HomeOwners Alliance puts a London single-storey extension at about £2,300 to £3,400 per m² for the building alone.
Is a kitchen extension more expensive than a normal extension?
Yes. Checkatrade suggests budgeting about £15,000 to £35,000 more than a plain room extension, because of plumbing, gas, electrics, boiler work and fitting the kitchen.
Do I need planning permission for a kitchen extension?
Not always. Many single-storey rear extensions can be built under permitted development if they meet every limit and condition, but flats, listed buildings, conservation areas and Article 4 areas change the picture. See our page on extension rules in London.
Should the builder supply the kitchen?
Either works. If you buy the kitchen separately, agree who fits it, who connects the services, and who is responsible if something does not fit. Make sure the builder’s quote says clearly what is excluded.
Sources
- Checkatrade – How much does a kitchen extension cost in 2026? (updated April 2026)
- Checkatrade – House extension cost guide
- HomeOwners Alliance – House extension costs
- Planning Portal – Fees for planning applications in England (from 1 April 2026)
- Checkatrade – Loft conversion cost guide (contingency advice)
- GOV.UK – Permitted development rights for householders: technical guidance
Sources checked on 20 October 2026. General information only, not legal, planning, structural or financial advice.
Related pages
- Extension builders in London
How to shortlist, check and compare extension builders in London before you sign anything. - Loft conversions in London
Velux, dormer, hip-to-gable and mansard lofts: permitted development limits, Building Regulations, Party Wall and London issues. - Loft conversion cost
2026 published loft conversion costs by type and per m², the cost breakdown, hidden extras and the London premium.