How Much Does a Terraced House Extension Cost in 2026? (UK)
In 2026 a terraced house extension typically costs £30,000–£50,000 for a single-storey rear extension, £40,000–£65,000 for a kitchen side-return, and £55,000–£90,000 for a double-storey rear — roughly £2,200–£3,400 per square metre before the kitchen and fit-out. Restricted access, party walls on both sides and carrying materials through the house all push terraced costs above the equivalent job on a detached home.
Terraced house extension cost — the short answer
- Single-storey rear extension (~12–15m²): £30,000–£50,000.
- Kitchen side-return extension: £40,000–£65,000.
- Double-storey rear extension: £55,000–£90,000.
- Typical build rate: £2,200–£3,400 per m² before the kitchen, flooring and fit-out.
- Biggest cost drivers: restricted access, party walls on both sides, glazing spec and kitchen quality.
The figures above are for the build. Add the kitchen, bathroom, flooring, decorating and professional fees (design, structural engineer, building control and any Party Wall surveyor) and the all-in project total is usually 15–30% higher than the shell-and-core build price.
Terraced House Extension Cost by Type (UK 2026)
Indicative build costs for a typical terraced house. Inc. VAT, before kitchen and fit-out.
Terraced extensions sit at the higher end of the per-m² range because access is tight, there is often no side gate, and materials and spoil have to be carried through the house — all of which adds labour time.
What Moves a Terraced Extension Quote Up or Down
Access & logistics
No side access means everything is carried through the house, and spoil is barrowed out the front. This slows the build and is the main reason terraces cost more per m² than semis or detached homes.
Party walls on both sides
A mid-terrace shares walls with two neighbours, so you usually need Party Wall awards on both sides — surveyor fees and notice periods to budget for and schedule early.
Glazing & roof
Bi-fold or sliding doors, roof lanterns and large rooflights bring in light on a deep terraced plan but add several thousand pounds over standard windows and a simple flat roof.
Kitchen & fit-out quality
Most rear and side-return extensions become the kitchen-diner. The units, worktops, appliances and flooring you choose can swing the all-in total by £15,000 or more.
Common Questions
Related Guides
More cost and planning guides for your extension project.
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