House Extension Cost in Oxford
2026 guide to realistic prices per square metre, itemised breakdowns, and budget tips.
Honest answer from a builder who prices these projects every week: in Oxford, expect £2,800–£3,500 per square metre for a single-storey extension built to a good specification.
Here's what that means in practice — and what moves the number up or down.
Typical project costs in Oxford (2026)
| Project Type | Typical Size | Typical Cost (2026) |
|---|---|---|
| Small rear kitchen extension | 15m² | £42,000–£52,500 |
| Standard rear extension | 20m² | £56,000–£70,000 |
| Side return infill (terrace) | 12m² | £38,000–£48,000 |
| Wrap-around extension | 30m² | £84,000–£105,000 |
| Double-storey extension | 40m² (two floors) | £95,000–£130,000 |
Figures are build costs including standard finishes. VAT, professional fees and premium kitchens/glazing are additional. Every Crawford quote is itemised line by line, so you see exactly where each pound goes.
Why Oxford costs more than the national average
Oxford build costs sit above the UK average for three reasons: restricted site access on terraced streets (scaffolding, skip permits, hand-digging where machines can't reach), conservation-area material requirements (matching brick, lime mortar, timber sash detailing), and strong local demand for skilled trades. Learn more about conservation area boundaries and permits in our planning permission guide.
What's included in a proper fixed-price quote
A genuine itemised quote should cover: groundworks and foundations, structural steels and calculations, masonry and roofing, windows and glazed doors, first and second fix electrics and plumbing, plastering and decoration, building control fees, and scaffolding and waste.
If a quote you're comparing is vague on any of these, that's where the "surprise" costs appear later. Crawford quotes fix all of it in writing before we start — and payments are staged against completed milestones, never large sums upfront.
What affects your price most
- Glazing — Sliding or bifold door walls and structural rooflights are beautiful but are often 10–15% of the whole budget.
- Kitchen specification — The same extension can carry a £15,000 or a £60,000 kitchen.
- Structural openings — Removing rear walls needs steel; steel needs calculations, crane access and building control sign-off.
- Ground conditions — Oxford's clay soils and high water tables in areas near the Thames and Cherwell can require deeper foundations.
- Conservation requirements — Handmade bricks and heritage details cost more than modern equivalents, but protect your property's value.
Get a real number, not an estimate
Online calculators can't see your house. We can — our free site consultation gives you a genuine itemised, fixed-price figure for your exact project, usually within a week of visiting. Before booking a site visit, you can get a realistic cost range in under a minute with our house extension cost calculator.
Get Your Free Quote
Ready to budget with real figures? Book a free site visit for an itemised, fixed-price quote on your Oxford extension.
Professional Fees Note
Budget figures cover building work and standard interior finishing. Professional fees (architects, surveyors, engineers) typically add 10-15% of build costs.
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