Tell us about your extension
Start with your postcode, address, approximate size and what you already have. You can say “not sure”.
How it works
Understand your project. Choose your next step.
A useful starting point whether you have an idea, drawings or approvals already in place.
Understand the next step
See your council, an early cost breakdown and the parts of your project that need checking.
Ask for the help you need
Save your project. Request designers, builders or engineers separately, or bring your existing quotes. The team assesses requests before any outside sharing.
Available in this beta: save your extension project, request each service separately and compare quotations you already have. The team reviews requests first. Postcode search lists researched firms across the UK, separately labelled from CYB-approved firms with confirmed coverage. Confirm each firm’s service area and availability. Verified customer reviews are not available yet.
Your details, your choice
We require your project postcode and address to tailor the assessment. You can view your initial result without giving a phone number or email. Photos and documents are optional.
Unsent answers stay in this tab until you refresh or close it. Choose Save my extension project to keep your brief in your signed-in account and return later.
How help requests work
Choose a separate comparison for a designer, builder or structural engineer. Each request is saved for the team to assess first. We ask before sharing information with outside professionals. Submitting a request does not appoint a professional or guarantee quotations.
You can record real quotations, keep their original files and compare their scope. Postcode search shows researched firms and, when available, CYB-approved firms with confirmed coverage. Each listing makes its verification status clear. Requests still go to our team first, and do not automatically contact those firms.
What a useful comparison should show
The same project brief, the actual provider, price and VAT, included work, exclusions, allowances and timing. A single quotation should be shown as one offer, and any connection to our own team should be clear.
The initial calculator is a budgeting guide. Its planning indication depends on your answers and the checks it supports; it is not a decision from your council.