Grand Designs Live London 2020 will now take place on 22-31 August

Find out more


Powered by Grand Designs Magazine

A house extension could add value to your home. If you are planning to extend your property why not use our free cost calculator to get a quick estimate of your build costs.


Once you have an idea of the financials it’s time to make your extension a reality. Book your ticket to Grand Designs Live for access to 450+ companies specialising in products and services in build, interiors, kitchens, bathrooms, gardens, technology and more!

Please note:
This information is computer-generated and has been designed to give a useful general indication of costs. We recommend that you obtain exact figures from a specific lender before committing to any mortgage.


Tell us about what you need


Size of Extension

Image of layout
Image of layout

Roof Style*

Extension Options

Tell us about yourself

Thank you for using our cost calculator.

Please provide your name and email to complete your quote.

Please tick here to receive emails to keep you up to date with our latest announcements, news, competitions, offers and discounts from The Grand Designs Live and our sister magazine Good Homes
You can opt out at any time by using the link provided in every email. Your personal information will only be used as set out in our privacy policy.

Book Tickets