How Much Does a House Extension Cost?

You don't need another generic business article. Here's what I'd tell a mate in Bristol who's on the tools five days a week.

You don't need to post daily on social — you need a site that still looks alive when someone finds you at 9pm on a Sunday.

A single-storey rear extension commonly falls in a £40,000–£70,000 band for many UK homes once foundations, structure, openings, roof tie-in, and basic finishes are included — but spec swings this wildly.

Two storeys aren't simply double — shared foundations and scaffolding can change the maths. Architect fees, planning, building control, kitchens, and bi-fold doors are often extras people forget.

Ballpark figures help — exact quotes need a visit

UK prices swing by region, access, spec, and who's supplying materials. Treat ranges below as starting points, not promises.

Always put allowances in writing for unknowns (asbestos, rotten joists, failed damp tests). That's how "how much does a house extension cost" stays fair for you and the customer.

What's included changes the number

Scaffolding, waste removal, making good, and VAT status all shift totals. Compare quotes line by line, not headline price alone.

Prices move with access, spec, and who's supplying materials — treat any guide as a starting point, then quote properly after you've seen the job.

Timelines depend on trades stacking

A bathroom isn't 'two weeks' if the plumber, tiler, and electrician can't align. Good planning beats optimistic guesses.

Always put allowances in writing for unknowns (asbestos, rotten joists, failed damp tests). That's how "how much does a house extension cost" stays fair for you and the customer.

Planning rules save fines later

Permitted development and building regs aren't optional extras. When in doubt, check the local council portal before you price the job.

Prices move with access, spec, and who's supplying materials — treat any guide as a starting point, then quote properly after you've seen the job.

What to do this week

Pick one change from this article and do it before Friday. If your online presence is thin, start there — it's the bit that works while you're on site.

1. Write down your current process — quotes, follow-ups, or how customers find you
2. Fix the weakest step (even if it's just a voicemail greeting)
3. Tell one happy customer they can mention you online if they were pleased
4. Review your website on your phone — would you hire you?

Worth remembering

None of this replaces good workmanship. But in 2026, the trades winning steady work in Bristol and everywhere else tend to combine solid on-site skill with a business that looks organised online. You don't need to be flashy — just clear, reachable, and professional.