Key Takeaway
How much does a house extension really cost in Winchester? We break down real build costs by type, the design fees, planning fees and what affects total project cost.
Winchester is one of Hampshire's most desirable addresses — and one of its most complex planning environments. Whether you're in a Victorian terrace near the city centre, a 1970s semi in Stanmore, a detached house in Kings Worthy or a period property in a surrounding village, the total cost of an extension depends on a predictable set of variables. This guide gives you a realistic picture of what to budget.
Build Costs for Winchester Extensions in 2026
Build costs are what you pay your contractor to construct the extension. Hampshire Build doesn't provide these — we provide the design and planning services that enable your contractor to price the build accurately. Current Winchester contractor pricing:
- Single-storey rear extension (mid spec): £1,800–£2,500 per m²
- Single-storey rear extension (high spec, oak frames, bifold doors, lantern): £2,500–£3,200 per m²
- Two-storey side or rear extension: £1,600–£2,200 per m² (more efficient per m² than single-storey)
- Loft conversion: £35,000–£75,000 depending on type and finish
- Garage conversion: £800–£1,500 per m²
These are shell and core costs — they exclude kitchen, bathroom fittings, decoration, floor coverings and furniture. A 30m² kitchen extension costing £55,000–£75,000 to build will often need another £15,000–£25,000 in finishes to be complete.
Winchester Planning Application Fees in 2026
Householder planning applications at Winchester City Council cost £258 (increased from April 2025). If your extension is within Permitted Development Rights, you can apply for a Lawful Development Certificate instead — also £258 — which gives you formal confirmation that no planning permission was required.
Listed building consent applications at Winchester cost £258 for minor works. If your property is listed, any external extension and many internal alterations require this as well as planning permission.
Design Fees: Hampshire Build Fixed Packages
Hampshire Build's design fees are fixed and published. There is no hourly charging and no risk of cost escalation:
- Pre-Build Package: £1,950 + VAT — planning drawings, planning application submission and building regulations drawings
- Premium Package: £2,950 + VAT — adds specification writing and contractor tendering support
- Premium Plus Package: £4,950 + VAT — adds two site visits with written reports, contract administration and unlimited design revisions
Winchester-Specific Cost Factors
Winchester City Council's conservation area policy and design standards add cost to some projects:
- Conservation area extensions: Brick matching, traditional window proportions and specific material requirements are often stipulated. Your contractor's material costs are higher, and the design process may require pre-application consultation with Winchester's officers (+£200–£500 if we request a formal pre-app).
- Listed buildings: Structural interventions in listed buildings require more careful specification. Building contractors typically price a premium of 15–25% over standard extension costs for listed building work.
- Archaeological surveys: Winchester's historic city centre sits on significant Roman and medieval archaeology. Extensions requiring deep excavation may trigger an archaeological investigation requirement — costs vary but allow £2,000–£8,000 as a contingency if your property is within the city's archaeological constraint area.
Total Winchester Extension Project Budget
A typical 25m² single-storey rear kitchen extension in Winchester might total:
- Design fees (Hampshire Build Pre-Build): £1,950 + VAT
- Planning application fee: £258
- Build (mid-spec, 25m² at £2,000/m²): £50,000
- Kitchen supply and fit: £12,000–£20,000
- Decoration and floor coverings: £3,000–£6,000
- Total: £70,000–£82,000 + VAT on build and finishes
Use our Extension Cost Calculator for a project-specific estimate, or book a complimentary consultation with our Winchester-based team.
