Guide to Budgeting for a Home Renovation or Extension in the UK

How to plan your budget from first ideas to finished build.

Why Proper Budgeting Matters

One of the most common reasons home projects stall — or become far more stressful than they need to be — is poor budgeting. It’s not just about setting aside enough for construction.

There are architect’s fees, specialist consultants, statutory costs, VAT, and often a few surprises along the way.

This guide will help you create a realistic budget so you can make informed decisions from the start — and avoid running out of funds mid-project.

1. Start with Your Construction Budget

Construction is almost always the largest part of your spend. For UK home extensions and renovations, a broad guide is:

  • Basic finish: £2,000–£2,500 per m²

  • Mid-range finish: £2,500–£3,500 per m²

  • High-end finish: £3,500+ per m²

Example:

A 30m² kitchen extension at mid-range spec:

£2,800 × 30m² = £84,000 (construction only).

2. Add Professional Fees

Architect’s Fees

  • Full service: 10–15% of construction cost for most projects.

  • More complex projects or listed buildings may be slightly higher.

Structural Engineer

  • £2000–£4,000 depending on complexity (steel beams, foundation changes, etc.).

Party Wall Surveyor

(if required)

  • £900–£1,800 per surveyor — and you may need to pay for your neighbour’s surveyor too.

Building Regulations / Approved Inspector

  • £750–£1,500 for a private approved inspector.

  • Slightly less if going through local authority, but service can be slower.

CCTV Drain Survey

(if building over or near drains)

  • £250–£500.

Other Specialists (if needed)

  • Heritage or Conservation Consultant: £800–£2,500.

  • Energy / SAP Assessor: £300–£700.

  • Arboricultural (Tree) Survey: £300–£800.

3. Include Statutory Costs

Planning Application Fees

(England)

  • Householder application: £528.

  • Listed Building Consent: No fee (but still requires detailed drawings).

4. Don’t Forget VAT

  • Most residential projects attract 20% VAT on construction and professional services.

  • VAT exceptions:

    • Some work to listed buildings may be VAT exempt.

    • New builds can be zero-rated.

Example:

£84,000 build cost + £20% VAT = £100,800.

5. Contingency

Even with careful planning, unexpected costs arise — hidden structural issues, material price rises, or client-led changes.

  • Allow 10–15% of your total budget for contingency.

6. Example Budget Breakdown – 30m² Kitchen Extension (Mid-Range Spec)

Item Cost Estimate

Construction £84,000

Architect (13%) £10,920

Structural Engineer £3,500

Party Wall Surveyor £1,500

Building Regulations £1,000

CCTV Drain Survey £350

Planning Fee £528

Contingency (10%) £10,179

Subtotal £111,977

VAT @ 20% £22,395

Total Estimated Budget £134,372

7. Tips for Staying on Budget

  1. Be upfront about your budget with your architect — we can design to it.

  2. Get detailed quotes, not just ballpark figures, before starting work.

  3. Make design decisions early to avoid costly mid-project changes.

  4. Factor in finishes (kitchens, bathrooms) — these can swing costs massively.

  5. Don’t spend contingency until the final stages unless unavoidable.


Need help setting a realistic budget?

I offer a £150 on-site consultation where we’ll explore your ideas, assess your property, and outline a clear cost framework before you commit to the next stage.

To Book Your Consultation: Email at studio@natureworksdesign.co.uk or call me on 0203 304 2338.