House Extension Cost Hampshire 2026: Budget Guide

Key Takeaway

A practical 2026 guide to Hampshire house extension costs, the factors that shape a project budget and what to include beyond the builder's price.

House Extension Cost Hampshire 2026: What to Budget For

Start by defining the size, layout and specification you have in mind, then allow separately for construction, design, statutory fees, fit-out and contingency. Our extension cost calculator can help you form an initial project-specific estimate; it is a starting point, not a contractor quote.

One of the first questions Hampshire homeowners ask is 'how much will my extension cost?' The answer depends on size, specification, location, and additional costs. This guide explains key budget considerations for Winchester, Basingstoke and Southampton.

Amounts in the older examples below are historical estimates, not current or verified 2026 prices. Costs vary by project and contractor; use our free cost calculator for an initial estimate and verify current prices and statutory fees before budgeting.

Total Extension Cost Breakdown: Historical Examples

For a typical 30m² single-storey kitchen extension:

• Design fees: £1,950-£2,950 + VAT (3-5% of total project)
• Planning fee: Check the current fee with the relevant local planning authority.
• Building regulations: the current published fee (council fee)
• Construction: £54,000-£105,000 + VAT (90-95% of total project)
• Total project: £56,000-£109,000 + VAT for 30m² extension

Design and Planning Costs

Architectural Design Fees

Hampshire Build Fixed-Fee Packages:

• Pre-Build Package: £1,950 + VAT (planning + building regs — most popular)
• Premium Package: £2,950 + VAT (adds contractor tender + contract)
• Premium Plus Package: £3,950 + VAT (includes the staged programme of works and statutory notices before the build starts)

Traditional Hourly-Rate Designers:

• Junior designers: £60-£80 + VAT/hour (total project: £2,400-£4,800 + VAT)
• Experienced designers: £80-£120 + VAT/hour (total project: £3,200-£7,200 + VAT)
• Senior/chartered designers: £120-£180 + VAT/hour (total project: £4,800-£10,800 + VAT)
• Your savings with fixed-fee: £1,050-£8,850

Structural Engineering Costs

• Steel beam calculations: £400-£800 + VAT
• Foundation design: £400-£800 + VAT
• Complete structural package: £800-£2,000 + VAT
• Included in our Pre-Build Package

Planning Application Fees

• Householder planning: the current published fee (council fee)
• Prior Approval: £240 + VAT (for larger Permitted Development extensions)
• Listed building consent: £528 + VAT (in addition to planning)
• Conservation area: £528 + VAT (same as standard planning)

Building Regulations Fees

Winchester City Council:

• Small extensions (<40m²): £550-£650 + VAT
• Medium extensions (40-100m²): £650-£800 + VAT

Basingstoke & Deane Council:

• Single-storey: £500-£700 + VAT
• Two-storey: £700-£850 + VAT

Southampton City Council:

• Single-storey: £520-£680 + VAT
• Two-storey: £680-£850 + VAT

Construction Costs Hampshire (per m²): Historical Examples

Single-Storey Extensions

Basic Specification (£1,800-£2,200 + VAT/m²):

• Standard brick matching existing
• Flat roof with 2 roof lights
• Basic aluminum bi-fold doors (3m)
• IKEA or Howdens kitchen
• Standard porcelain tiles
• No underfloor heating

Good Specification (£2,200-£2,800 + VAT/m²):

• Quality brick or render finish
• Flat roof with lantern or 4 roof lights
• Mid-range bi-fold doors (4-5m)
• Magnet or Wren kitchen
• Large-format tiles or engineered oak
• Underfloor heating throughout

High Specification (£2,800-£3,500 + VAT/m²):

• Handmade brick or premium render
• Structural glass roof or large lantern
• Premium slim-frame bi-folds (5-6m)
• Bespoke kitchen (Benchmarx, John Lewis)
• Premium flooring (natural stone, wide oak boards)
• Underfloor heating + smart controls
• High-end lighting design

Two-Storey Extensions

Basic Specification (£1,600-£2,000 + VAT/m²):

• Matching brick construction
• Standard windows and doors
• Basic kitchen downstairs
• Standard bedroom/bathroom fittings upstairs
• Carpet upstairs, basic tiles downstairs

Good Specification (£2,000-£2,500 + VAT/m²):

• Quality brick and roof tiles
• Bi-fold doors downstairs
• Good quality kitchen
• En-suite bathroom with quality fittings
• Engineered wood flooring
• Underfloor heating ground floor

High Specification (£2,500-£3,200 + VAT/m²):

• Premium materials throughout
• Large bi-folds + roof lights
• Bespoke kitchen downstairs
• Luxury en-suite with underfloor heating
• Premium flooring both floors
• Smart heating and lighting

Hampshire Extension Cost Examples

Example 1: Winchester Kitchen Extension (30m² Single-Storey)

• Size: 6m x 5m = 30m²
• Spec: Good quality (bi-folds, underfloor heating, Wren kitchen)
• Design fees: £1,950 + VAT (Pre-Build Package)
• Planning: £0 + VAT (Permitted Development)
• Building regs: £580 + VAT
• Construction: 30m² x £2,400 + VAT/m² = £72,000 + VAT
• Total project: £76,870 + VAT

Example 2: Basingstoke Side Return (18m² Single-Storey)

• Size: 6m x 3m = 18m²
• Spec: Basic (standard doors, no underfloor heating)
• Design fees: £1,950 + VAT (Pre-Build Package)
• Planning: Check the current Prior Approval fee with the relevant local planning authority.
• Building regs: £520 + VAT
• Construction: 18m² x £2,000 + VAT/m² = £36,000 + VAT
• Total project: £39,590 + VAT

Example 3: Southampton Two-Storey (40m² Total)

• Size: 5m x 4m each floor = 40m² total
• Spec: Good quality (kitchen downstairs, bedroom + en-suite upstairs)
• Design fees: £1,950 + VAT (Pre-Build Package)
• Planning: £528 + VAT
• Building regs: £720 + VAT
• Construction: 40m² x £2,200 + VAT/m² = £88,000 + VAT
• Total project: £93,268 + VAT

Example 4: Winchester Conservation Area Orangery (35m²)

• Size: 7m x 5m = 35m²
• Spec: High (brick pillars, glazed lantern, premium kitchen)
• Design fees: £2,950 + VAT (Premium Package - conservation area)
• Planning: £528 + VAT (conservation area planning)
• Building regs: £650 + VAT
• Construction: 35m² x £3,200 + VAT/m² = £112,000 + VAT
• Total project: £119,398 + VAT

Hidden Costs Hampshire Homeowners Forget

During Construction

• Temporary kitchen: £500-£1,500 + VAT (microwave, mini-fridge, camping stove)
• Eating out: £800-£2,000 + VAT (3-4 months no proper kitchen)
• Skip hire: £400-£800 + VAT (2-4 skips during build)
• Scaffolding: £800-£1,500 + VAT (if not included in builder quote)
• Utilities disconnection/reconnection: £300-£600 + VAT
• Building Control inspection fees: Included in BC fee

After Construction

• Interior decoration: £1,500-£4,000 + VAT (painting, finishing)
• Furnishing: £3,000-£10,000 + VAT (dining table, sofas for new space)
• Kitchen appliances: £2,000-£8,000 + VAT (if not in builder quote)
• Landscaping reinstatement: £1,500-£5,000 + VAT (lawn, paving, fencing)
• Cleaning: £300-£600 + VAT (deep clean after builders)

Contingency Costs

• Ground conditions: £1,000-£5,000 + VAT (if clay deeper than expected)
• Drainage issues: £500-£3,000 + VAT (existing drains need rerouting)
• Structural surprises: £1,000-£4,000 + VAT (weak walls, asbestos removal)
• Design changes mid-build: £500-£3,000 + VAT (client requests changes)
• Recommended contingency: 15-20% of construction cost

How to Reduce Extension Costs in Hampshire

Design Stage Savings

• Fixed-fee design packages: Save £2,000-£4,000 vs hourly designers
• Permitted Development: Save the current published fee planning fee + 8 weeks time
• Simple rectangular shape: 15% cheaper than complex shapes
• Standard sizes: Use standard door/window sizes

Construction Savings

• Builder directly: 10-15% cheaper than using main contractor
• Off-season build: November-March often 5-10% cheaper
• Material choices: Aluminum bi-folds vs premium slim-frame saves £2,000-£4,000 + VAT
• Flat roof: £3,000-£6,000 + VAT cheaper than pitched roof for 30m²
• IKEA kitchen: £4,000-£8,000 + VAT cheaper than bespoke

What NOT to Skimp On

• Foundations: Hampshire clay needs proper depth
• Insulation: current Part L requirements essential
• Bi-fold door quality: Cheap doors fail within 5-10 years
• Underfloor heating: Hard to retrofit later, worth £2,000 + VAT investment
• Building regulations: Never skip - expensive to fix later

Extension Costs by Size: Historical Examples

Size	Type	Basic Spec	Good Spec	High Spec
20m²	Single-storey	£36,000-£44,000 + VAT	£44,000-£56,000 + VAT	£56,000-£70,000 + VAT
30m²	Single-storey	£54,000-£66,000 + VAT	£66,000-£84,000 + VAT	£84,000-£105,000 + VAT
40m²	Single-storey	£72,000-£88,000 + VAT	£88,000-£112,000 + VAT	£112,000-£140,000 + VAT
40m²	Two-storey	£64,000-£80,000 + VAT	£80,000-£100,000 + VAT	£100,000-£128,000 + VAT
60m²	Two-storey	£96,000-£120,000 + VAT	£120,000-£150,000 + VAT	£150,000-£192,000 + VAT

Table shows construction costs only - add design fees, planning, building regs, and contingency

Winchester vs Basingstoke vs Southampton: Cost Differences?

Construction costs vary with property, specification, site conditions and contractor:

• Winchester: £2,200-£2,800 + VAT/m² average (slightly higher due to affluent area)
• Basingstoke: £2,000-£2,600 + VAT/m² average (lower due to more competition)
• Southampton: £2,100-£2,700 + VAT/m² average (similar to Winchester)
• Rural Hampshire: £2,300-£3,000 + VAT/m² (travel costs, less competition)

Financing Your Hampshire Extension

Payment Options

• Savings: Most cost-effective (no interest)
• Remortgage: 3-6% interest typical (spread cost over 25 years)
• Home improvement loan: 6-12% interest (5-10 year term)
• Personal loan: 8-15% interest (1-7 year term)

Builder Payment Schedule

• Deposit: 10-15% upfront
• Stage payments: 25% at foundations, 25% at roof, 25% at first fix
• Final payment: 15% on completion
• Never pay 100% upfront!

Hampshire Build's Transparent Pricing

Our packages provide certainty on design costs upfront:

• Pre-Build Package £1,950 + VAT: Drawings + planning application
• Pre-Build Package £1,950 + VAT: Planning drawings, Building Notice-ready building regulation drawings and required structural calculations by an independent qualified engineer
• Premium Package £2,950 + VAT: Adds tender support to two vetted contractors, cost proposals and a client-focused building contract issued for signature

All packages include an on-site measured survey, planning drawings and building regulation drawings prepared for Building Notice submission, with required structural calculations prepared by an independent qualified structural engineer. Premium adds tender support and Premium Plus adds a staged programme and specified notices.

Ready to budget accurately for your Hampshire extension? Book a free cost consultation or view our transparent fixed-fee packages serving Winchester, Basingstoke, Southampton, and all Hampshire areas.

More Useful Resources

• Extension cost calculator — get an instant personalised estimate in minutes
• Kitchen extension cost Hampshire 2025 — detailed pricing for kitchen extensions
• House extensions Basingstoke — local cost examples and planning guidance
• Garage conversions Winchester — a cost-effective alternative to extending
• Permitted Development rights guide — when you don't need planning permission

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