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.
How do project costs and planning routes compare?
Extensions add to the building, while loft and garage conversions work with existing space; each has different structural and planning considerations.
| Project | Typically needs planning? | Main cost factors | Typical design route |
|---|---|---|---|
| Single-storey extension | Property-specific planning assessment | Footprint, foundations and specification | Survey, layout, planning check and technical drawings |
| Two-storey extension | Planning route assessed for your design | Structure, roof design and specification | Survey, planning check and coordinated structural information |
| Loft conversion | Planning route assessed for your roof design | Roof type, stairs and structural work | Roof and layout assessment, planning check and Building Regulations |
| Garage conversion | Property-specific planning assessment | Insulation, structure and services | Survey, planning check and Building Regulations design |
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.
Have a project in mind? Start with a few details about your home.
Build an initial project budgetBuild 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 + VAT per m²
- Single-storey rear extension (high spec, oak frames, bifold doors, lantern): £2,500–£3,200 + VAT per m²
- Two-storey side or rear extension: £1,600–£2,200 + VAT per m² (more efficient per m² than single-storey)
- Loft conversion: £35,000–£75,000 + VAT depending on type and finish
- Garage conversion: £800–£1,500 + VAT 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 + VAT to build will often need another £15,000–£25,000 + VAT in finishes to be complete.
Winchester Planning Application Fees in 2026
Householder planning applications at Winchester City Council cost £258 + VAT (increased from April 2025). If your extension is within Permitted Development Rights, you can apply for a Lawful Development Certificate instead — also £258 + VAT — which gives you formal confirmation that no planning permission was required.
Listed building consent applications at Winchester cost £258 + VAT 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 package fees are fixed for the stated scope:
- Pre-Build Package: £1,950 + VAT — planning drawings, planning application submission and building regulations drawings
- Premium Package: £2,950 + VAT — adds contractor tender support, two cost proposals, a schedule of works and a client-focused building contract issued for signature
- Premium Plus Package: £3,950 + VAT — includes a staged programme of works, Building Notice submission and one Party Wall notice to one adjoining owner.
Winchester-Specific Cost Factors
Winchester City Council's conservation area policy and design standards add cost to some projects:
Ready to apply these ideas to your own home?
Check your project costs- 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 + VAT 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 + VAT 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: the current published fee
- Build (mid-spec, 25m² at £2,000 + VAT/m²): £50,000 + VAT
- Kitchen supply and fit: £12,000–£20,000 + VAT
- Decoration and floor coverings: £3,000–£6,000 + VAT
- 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.
A useful next step for your home
Share a few project details to explore an initial budget and planning view.
