Disclaimer

General notice

Extension Cost Calculator provides estimated costs for planning purposes only. The figures shown by the calculator are indicative, UK-based and generated from typical project data, user inputs and built-in assumptions.

Calculator results are not quotes, guarantees or fixed prices. They should not be used as the basis for contracts, commitments or final project budgets.

Professional advice

Before starting work or making financial decisions, you should speak to appropriate qualified professionals. This may include a builder, architect, structural engineer, planning consultant, building control professional or other specialist depending on the project.

Building costs can vary significantly by location, specification, access, ground conditions, design complexity, materials, contractor pricing and regulatory requirements.

No liability

To the fullest extent permitted by law, we accept no liability for loss, damage, cost or inconvenience arising from reliance on estimates or information provided by this site.

The calculator cannot account for every project variable, site-specific issue or change in market conditions.

Estimate accuracy

We aim to keep estimates useful and review them periodically, but they may not always reflect the latest prices or circumstances in your area. All prices are expressed in GBP and are intended for UK-based projects.