Are you starting to feel like your home is bursting at the seams? Maybe you've added to your family, started working from home, or simply realised that your kitchen feels half the size it did five years ago. If you're a homeowner in Bournemouth, Poole, or Christchurch, you've probably already looked at local house prices and thought: "Is it really worth moving, or should we just extend?"
The good news? A well-planned house extension can transform your home, add serious value to your property, and cost a fraction of what you'd spend on stamp duty, solicitors, and removal vans. The not-so-good news? If you don't know what you're getting into, costs can spiral quickly.
This guide breaks down exactly what you'll pay for a house extension in Bournemouth in 2026 : no vague estimates, no nasty surprises. Plus, there's a free quote checklist at the end to make sure you're comparing builders properly.
Ready to skip ahead and get a tailored estimate for your project? Try our free House Extension Calculator or get in touch for a no-obligation quote.
What Does a House Extension Cost in Bournemouth in 2026?
Let's cut straight to the numbers. For a typical single-storey extension in Bournemouth and the surrounding areas, you're looking at £2,200 to £3,300 per square metre : which is in line with South of England pricing.
What does that mean in real terms? Here's how it stacks up:
| Extension Size | Estimated Cost Range |
|---|---|
| 20m² (small rear extension) | £40,000 – £56,000 |
| 30m² (standard kitchen extension) | £60,000 – £84,000 |
| 50m² (large open-plan living space) | £100,000 – £140,000 |
| 60m² two-storey extension | £108,000 – £180,000 |
These figures assume a mid-range specification. If you're after premium finishes, glazed bi-fold doors, or a high-end kitchen fit-out, expect to land at the higher end : or beyond.
What Actually Affects Your Final Price?
You've seen the ballpark figures, but your quote could look very different depending on a few key factors. Here's what drives the real cost of your Bournemouth house extension:
1. Design Complexity
A simple rectangular rear extension with a flat roof is the most budget-friendly option, typically coming in around £1,900 to £2,400 per square metre. Add in vaulted ceilings, skylights, structural glass, or wrap-around designs, and you're looking at £2,400 to £3,200+ per square metre.
2. Quality of Finishes
Your extension is only as good as what goes inside it. Basic flooring, standard kitchen units, and simple lighting will keep costs down. But if you're dreaming of underfloor heating, bespoke joinery, or a showroom-worthy kitchen island, factor in an extra £7,500 to £30,000+ just for the fit-out.
3. Site Conditions
Older properties in Bournemouth and Christchurch sometimes throw up surprises : poor drainage, tricky access, or the need for underpinning. A reputable builder will survey your site properly before quoting, so you're not hit with unexpected costs mid-build.
4. Professional Fees
Architects, structural engineers, and building control officers all add to the bill. For a typical 30m² extension, expect roughly:
- Structural engineer: £1,500 – £2,500
- Architectural drawings: £1,500 – £4,000
- Building control fees: £400 – £1,000
These fees usually account for around 10% of your total project cost.
Hidden Costs You Might Not Have Considered
Beyond the build itself, there are a few extras that catch homeowners off guard. Make sure you budget for:
- Planning application fee: £206 (standard in England)
- Party wall agreement: £700 – £1,500 per neighbouring property (if your extension is on or near a boundary)
- Site surveys: Several hundred pounds for drainage, structural, or land surveys
- Temporary accommodation: If the build significantly disrupts your kitchen or bathroom, you may need to factor in eating out or staying elsewhere for a short period
The best way to avoid budget shocks? Work with a builder who provides a fixed-price guarantee upfront. That way, you know exactly what you're paying before a single brick is laid.
Want clarity on costs before you commit? Contact The Big Conversion Company for a transparent, fixed-price quote with no hidden fees.
Where Does Your Money Actually Go?
It's helpful to understand how your budget breaks down across a typical extension project. For a 30m² single-storey extension costing around £82,500 at mid-range spec, here's roughly where your money goes:
| Category | Percentage | Approx. Cost |
|---|---|---|
| Structure & shell (foundations, walls, roof, windows) | 60% | £49,500 |
| Internal fit-out (plumbing, electrics, kitchen, flooring) | 30% | £24,750 |
| Professional fees & admin (architect, building control, planning) | 10% | £8,250 |
This breakdown helps you see why "shell-only" quotes can be misleading. Always ask builders whether their price includes internal fit-out or just the structure.
Your Free Quote Checklist
When you're comparing quotes from builders in Bournemouth, Poole, or Christchurch, use this checklist to make sure you're comparing apples with apples:
✅ Scope definition : Are exact dimensions, room type, and single/double-storey clearly stated?
✅ Finish specification : Is the quote based on budget, mid-range, or premium materials?
✅ What's included : Does it cover shell-only or full internal fit-out (plumbing, electrics, flooring, decoration)?
✅ Timeline : Is there a clear expected completion date? Any penalties for overrunning?
✅ Professional services : Are architect and engineer fees included or separate?
✅ Permits and approvals : Who handles planning permission and building control applications?
✅ Additional costs : Are party wall agreements, site surveys, and kitchen upgrades factored in?
✅ Warranty : What's the defects liability period? Is workmanship guaranteed?
✅ Payment schedule : What deposit is required? When are milestone payments due?
✅ VAT : Is the quote inclusive or exclusive of VAT?
Pro tip: Always get at least 2–3 quotes in writing with detailed breakdowns. Prices can vary significantly between contractors, and the cheapest option isn't always the best value.
Why Bournemouth Homeowners Trust The Big Conversion Company
With over 18 years of experience delivering house extensions across Bournemouth, Poole, and Christchurch, we've built our reputation on doing things properly : no shortcuts, no surprises.
Here's what sets us apart:
- Fixed-price guarantee : The price we quote is the price you pay. No unexpected extras mid-project.
- Tailored designs : Every home is different. We design extensions that suit your lifestyle, your property, and your budget.
- On-time completion : We set realistic timelines and stick to them, because we know how disruptive building work can be.
- Fast, honest communication : You'll always know what's happening with your project. Questions answered, calls returned.
- Stress-free project management : From planning applications to final snagging, we handle the lot so you don't have to.
Whether you're dreaming of a spacious kitchen-diner, a ground-floor home office, or a two-storey extension to accommodate a growing family, we'll help you make it happen : on budget and on time.
Ready to Get Your Extension Project Started?
If you're serious about extending your Bournemouth home in 2026, the first step is understanding what's realistic for your budget and your property.
Use our free House Extension Calculator to get an instant ballpark figure, or book a free, no-obligation consultation with our team. We'll visit your property, discuss your ideas, and provide a detailed fixed-price quote : so you can make an informed decision with complete confidence.
Your dream extension is closer than you think. Let's make it happen.