Double Storey Extension Cost UK 2026

A double-storey extension adds two floors of space for roughly 60–80 % more than a single-storey because foundations and roof are shared. In 2026, expect £1,800–£2,600 per m² of floor area — meaning £75,000–£110,000 for a typical 40 m² double-storey rear.

Quick answer

Typical UK price range: £60,000–£160,000. Typical time: 14–20 weeks.

Free calculator

House extension calculator

Adjust the inputs to get an instant 2026 UK price estimate.

Extension type Single-storey rear Double-storey Side return Wrap-around Kitchen extension Oak frame

Extension floor area (m²)

Region London South East South West Midlands North of England Scotland Wales Northern Ireland

Specification level Basic / standard Mid-range Premium / high-end

Extras

Bi-fold doors £2,500–£6,000 Roof lanterns £1,500–£3,500 Underfloor heating £2,500–£5,000 New kitchen fit £8,000–£25,000 Architect & plans £2,500–£5,000

Lowest £—

Average £—

Highest £—

Estimate only. Prices reflect 2026 UK market data — get quotes from local tradespeople for accurate pricing.

Get 3 free quotes from vetted tradespeople

No signup. No spam. We pass your details only to vetted tradespeople (Checkatrade / MyBuilder / Bark partner network).

Name *

Email *

Phone *

Postcode *

Budget Under £5,000 £5,000 – £15,000 £15,000 – £30,000 £30,000 – £60,000 £60,000+ Not sure

Timeline As soon as possible 1 – 3 months 3 – 6 months 6+ months Just researching

Project details

I agree to be contacted by vetted local tradespeople and have read the Privacy Policy. Get 3 free quotes →

Key points

• £1,800–£2,600/m² — lower per-m² than single because of shared structure
• Almost always needs planning permission
• Adds a bedroom + a downstairs room — biggest value uplift
• Take 14–20 weeks on site

Cost breakdown

Item	Low	High
Foundations + groundworks	£8,000	£14,000
Two-storey structure	£35,000	£68,000
Roof + finishes	£6,000	£12,000
Glazing (windows + doors)	£4,500	£12,000
Electrics + plumbing + heating	£5,000	£10,000
Internal fit-out	£4,500	£10,000
Architect + planning + building control	£4,000	£8,000

Cost by UK region

Region	Typical cost
London	£148,500
South East	£137,500
South West	£121,000
Midlands	£110,000
North England	£99,000
Scotland	£104,500
Wales	£99,000

How to save money

• Allow 12–20 weeks for planning permission
• Specify a proper steel structural design — saves money long-term
• Match brick to the existing house — saves repainting later

How to find a trusted tradesperson

Get at least 3 quotes from vetted UK trade networks:

• Checkatrade
• MyBuilder
• Bark

FAQs

Do double-storey extensions need planning permission?

Yes, almost always. They’re not normally permitted development because they affect the roofline.

Get 3 free quotes

Submit your project details via the calculator above to receive 3 quotes from vetted tradespeople.

Disclaimer: Prices are guide ranges based on 2026 UK market data. Get quotes from local tradespeople for accurate pricing.