A transparent budgeting tool for early-stage extension projects. We show a low / expected / high range and separate build cost, extras, fees, contingency, and VAT to help homeowners plan realistically.
Why this is different
Step 1 of 5
Property
We use this to localise pricing and estimate realistic access/party wall allowances.
Helps us refine local pricing later. You can skip this if you're only exploring.
Accuracy note
This calculator is designed for early budgeting. We avoid asking specialist questions at this stage and widen the estimate range if plans are not ready yet.
This extension cost calculator is built for homeowners who need a more realistic starting budget before they move into planning, drawings, or detailed builder quotes. It helps you compare house extension cost ranges by size, type, finish level, and professional fees instead of relying on oversimplified online averages.
Whether you are looking at a single storey extension, double storey extension, or a more complex scheme, the calculator makes it easier to understand likely extension cost in London and to budget properly for extras, contingency, and VAT from the start.
FAQ
Frequently Asked Questions
It is designed for early budgeting, not a final quote. The tool gives a low / expected / high range and widens that range when you don't yet have plans or confirmed planning status.
Accuracy improves significantly once you have measured or architect drawings and a site survey.
Exact pricing before surveys and drawings is usually misleading. Build cost depends on structural details, access, specification, and hidden site conditions.
A transparent range is more trustworthy and more useful for budgeting decisions.
Yes. The result screen clearly separates base build cost, extras, professional/statutory fees, contingency, and VAT.
We apply VAT conservatively to the subtotal so you don't under-budget at the planning stage.
That's normal. The calculator is built for homeowners at an early stage. If you leave planning/professional fees unselected, it automatically includes sensible allowances based on your answers.
Better Homes primarily serves London, so London is the main pricing focus of this tool (including a zone option).
We also include other UK regions so homeowners can still use the calculator for budgeting comparisons.
Download the PDF, compare the expected and high ranges, then speak to an architect/designer or builder with your rough brief. Once you have plans, update the calculator and request a survey-based quote.
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Whether you're looking to transform your bathroom, renovate your kitchen, or undertake a complete home renovation, we're here to bring your vision to life with our signature blend of quality, reliability, and attention to detail.
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