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Speak to an Extension Designer

Hampshire's Trusted Extension Designers

Extension Cost Calculator — Get Your Instant Estimate

Get instant cost estimates for your extension project. Fixed-fee design packages include planning permission drawings and building regulations.

Call Now: 01722 548911 Complimentary consultation with our extension designers

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With real planning data for your area

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Select your extension type to continue

Estimates are for guidance only - not a binding quote. Shell/core costs exclude finishes, kitchens, bathrooms, and decoration. All costs exclusive of VAT. See Terms.

Extension Design Packages

Fixed-fee packages for planning permission drawings and building regulations. No hidden costs, no hourly rates.

Essential Package

Planning permission drawings

£1,350
+ VAT
  • Measured survey
  • Planning drawings
  • Planning application
Most Popular

Pre-Build Package

Building regulations drawings

£1,950
+ VAT
  • Everything in Essential
  • Building regulations
  • Structural calculations
Premium

Premium Package

Full project support

£2,950
+ VAT
  • Everything in Pre-Build
  • Tender process
  • Contract administration

Kitchen Extension & Rear Extension Examples

Real-world cost estimates for popular Hampshire extension projects designed by our team.

Kitchen Extension

4m × 4m = 16m²

Design (Pre-Build) £1,950 + VAT
Build Cost £32,000-48,000
Total Project £33,950-49,950

Rear Extension

5m × 5m = 25m²

Design (Pre-Build) £1,950 + VAT
Build Cost £50,000-75,000
Total Project £51,950-76,950

Side Return Extension

2m × 5m = 10m²

Design (Essential) £1,350 + VAT
Build Cost £20,000-30,000
Total Project £21,350-31,350

Extension Design FAQs

Common questions about planning permission drawings, building regulations, and working with extension designers.

Speak to a Hampshire Extension Designer

Book a free 30-minute consultation. We'll assess your project, discuss planning permission requirements, and give you a realistic budget.