Costs
House Extension Costs
A practical 2026 budgeting guide with current per-square-metre benchmarks, worked 20m² and 30m² examples, VAT, planning fees, common exclusions and the local factors that can change a quotation.
Building Guides
Reviewed by Daryl Edwards, Company Director · Updated October 2026
Clear project information helps homeowners make better decisions before building work begins. These guides explain common parts of planning, quotations, contracts and construction in practical language for people considering an extension, refurbishment or structural alteration in Cambridge and Cambridgeshire.
The articles are general information rather than project-specific legal, planning or engineering advice. Requirements vary with the property, drawings, site conditions, approvals and contract.
Eleven guides, grouped by what they cover. Each opens the full guide.
Costs
Budgets, worked examples and the cost calculator, by type of project.
Calculator
House Extension Cost Calculator
An itemised starting budget built from the same published figures — the 2026 construction range, planning application fees, VAT and contingency — and honest about the four costs only a written figure can pin down.
Costs
Loft Conversion Costs
2026 cost benchmarks by conversion type — rooflight, dormer, hip-to-gable and mansard — with worked examples, the head-height check that decides what is possible, the building regulations that always apply and the costs outside a builder’s price.
Costs
New Build House Costs
What it costs to build a new house here, why a new dwelling is zero-rated for VAT, the plot and ground conditions that move a budget most, and the Greater Cambridge planning picture including water efficiency and the Community Infrastructure Levy.
Costs
Repointing Costs
2026 benchmark rates per square metre, worked examples for a gable, a chimney and a whole house, why older gault-brick Cambridge houses usually need lime rather than cement, scaffold and access, and when repointing on its own is not the right repair.
Costs
Structural Alterations and Knock-Through Costs
What it costs to remove a load-bearing wall, fit a steel beam, take out a chimney breast or form an opening for bifold doors — with the engineer, Building Control and party wall costs that sit alongside the builder’s price.
Costs
House Refurbishment Costs
Light, full and back-to-brick refurbishment bands per square metre, room-by-room examples, the allowances older Cambridge houses need, landlord void refurbishments, and when the reduced 5% VAT rate can apply to an empty home.
Approvals: planning and Building Regulations
What needs permission, what can go ahead under permitted development, and how Building Regulations approval works.
Planning
Planning Permission
A practical guide to when a Cambridge extension needs permission, local restrictions, the householder application process, drawings, conditions and approvals before building.
Planning
Permitted Development
A practical guide to householder permitted development rights, extension and loft limits, local restrictions, prior approval, lawful development certificates and the checks needed before building.
Building Regulations
Building Regulations
A practical guide to approval routes, design information, 3C Building Control inspections and completion certificates for Cambridge house extensions.
Choosing a builder
What a quotation should contain before you compare prices or sign anything.
Quotations
What a Builder’s Quotation Should Include
A detailed checklist covering scope, exclusions, VAT, allowances, programme, stage payments, variations, insurance and written contract terms.
Use the guides with real project evidence
A useful guide should connect general advice with work that can be inspected. See our building project portfolio, including the Clay Street extension and refurbishment in Histon and the Herons Close extension in Cambridge.
You can also explore our services for house extensions, property refurbishment, brickwork and blockwork and structural alterations.
Turn your plans into a clear next step
Tell us what you want to achieve, and send whatever you already have. No drawings needed to start an enquiry: photos and drawings help, but plenty of projects begin with a description and a site visit.
What we need to quote
- Property address and brief
- Existing and proposed drawings
- Planning and structural information
- Preferred start window and budget range
Guides are reviewed periodically. Always use the current requirements and obtain appropriate professional advice for your property and project.