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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
Beautiful home extension with roof lantern and dining area

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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 Pre-Build Packages

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

Pre-Build Package
£1,950
+ VAT
Planning & Build-Ready Drawings
  • Professional on-site measured survey
  • Detailed planning drawings
  • Planning application submission
  • Full building regulation drawings
  • Certified structural calculations
Most Popular
Premium Package
£2,950
+ VAT
Contract Administration & Setup
  • Everything in Pre-Build Package, plus:
  • Detailed schedule of works
  • Professional contractor vetting
  • Contractor proposal gathering
  • Client-focused building contract
Most Complete
Premium Plus Package
£4,950
+ VAT
Structural Revisions & Site Visits Included
  • Everything in Premium Package, plus:
  • Site Set Up Meeting with client & contractor
  • Unlimited structural revisions — no cap, no extra charge
  • 2 on-site superstructure visits with written reports
  • Continual remote support throughout the build

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

Rear Extension

5m × 5m = 25m²

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

Side Return Extension

2m × 5m = 10m²

Design (Pre-Build Package) £1,950 + VAT
Build Cost £20,000-30,000
Total Project £21,950-31,950

Extension Design FAQs

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

Speak to a Hampshire Extension Designer

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