Key Takeaway
Use our free extension cost calculator to get instant estimates for your Hampshire extension. Calculate build costs from £1,800-£3,200/m², design fees, and total project costs. Updated for 2025 prices.
Extension Cost Calculator: Your Complete 2025 Hampshire Guide
Planning an extension in Hampshire? Our free extension cost calculator gives you instant, accurate estimates based on real 2025 construction costs. Whether you're considering a kitchen extension, two-storey addition, or wraparound design, understanding costs upfront is crucial for budget planning.
How Much Does an Extension Cost in 2025?
Extension costs in Hampshire vary significantly based on type, size, and specification. Here's what you can expect to pay per square metre in 2025:
Build Costs Per Square Metre (2025 Hampshire Prices)
- Single-Storey Extension: £1,800 - £2,400/m² (standard) to £2,400 - £3,200/m² (high specification)
- Two-Storey Extension: £1,600 - £2,200/m² (standard) to £2,200 - £2,800/m² (high specification)
- Kitchen Extension: £2,200 - £2,800/m² (includes kitchen fitting allowance)
- Side Return Extension: £2,400 - £3,200/m² (higher per m² due to smaller footprint)
- Loft Conversion: £1,400 - £2,000/m² (varies by type)
Using the Extension Cost Calculator
Our extension cost calculator asks four simple questions to generate your personalised estimate:
- Extension Type: Select from single-storey, two-storey, kitchen, side return, or wraparound
- Size: Enter your proposed floor area in square metres
- Finish Quality: Choose standard, mid-range, or high specification
- Your Details: Postcode for local planning insights
Within seconds, you'll receive a detailed cost breakdown including design fees, build costs, and total project budget. Try the calculator now .
What's Included in Extension Costs?
A complete extension project includes several cost elements:
Design & Professional Fees (10-15% of build cost)
- Extension design drawings and specifications
- Planning permission application (if required)
- Building regulations approval
- Structural engineer calculations
Hampshire Build offers fixed-fee design packages from £1,350+VAT, saving you £2,000-£4,000 compared to hourly rates.
Build Costs (Main Construction)
- Foundations and groundworks
- Structural steelwork
- Brickwork, roofing, and external finishes
- Windows, doors, and glazing
- First fix (electrics, plumbing, heating)
- Plastering and internal walls
- Second fix and decoration
Additional Costs to Budget For
- Planning application fees: £528 (householder application, as of April 2025)
- Building control fees: £400-£800
- Party wall agreements: £700-£1,000 per neighbour
- Kitchen fitting: £10,000-£30,000
- Landscaping and making good: £2,000-£5,000
Extension Cost Examples for Hampshire
Example 1: Single-Storey Kitchen Extension (25m²)
- Build cost (mid-range): £55,000 - £65,000
- Design package (Pre-Build): £1,950 + VAT
- Kitchen: £15,000 - £25,000
- Total: £72,000 - £92,000
Example 2: Two-Storey Rear Extension (40m²)
- Build cost (mid-range): £72,000 - £88,000
- Design package (Pre-Build): £1,950 + VAT
- Bathroom fitting: £5,000 - £10,000
- Total: £79,000 - £100,000
Example 3: Side Return Extension (15m²)
- Build cost (high spec): £48,000 - £60,000
- Design package (Essential): £1,350 + VAT
- Total: £50,000 - £62,000
Why Extension Costs Vary
Your actual extension cost depends on several factors:
- Location: Winchester, Southampton and Basingstoke have different labour rates
- Access: Restricted site access increases costs by 10-15%
- Ground conditions: Poor ground may require deeper foundations
- Specification: Bi-fold doors, roof lanterns, and underfloor heating add costs
- Complexity: Listed buildings and conservation areas require specialist input
Get Your Personalised Extension Cost Estimate
Ready to find out what your extension will cost? Our free extension cost calculator provides instant, personalised estimates based on 2025 Hampshire construction prices.
After using the calculator, you'll receive a detailed proposal by email with:
- Personalised cost breakdown
- Local planning authority insights
- Fixed-fee design package options
- Next steps to get started
