Do I need a lawful development certificate for an extension?
A lawful development certificate is not compulsory, but it is the clearest proof that an extension built under permitted development was lawful. In England an application for a proposed extension costs £274 from 1 April 2026, and councils should decide within eight weeks. Many buyers' solicitors ask for one when you sell.
What does a certificate actually confirm?
It confirms that the extension, as drawn, does not need planning permission because it falls within permitted development. It is a legal determination by the council, not an opinion, so it carries far more weight than a builder's assurance.
When is it worth getting one?
- When the extension is close to the permitted development limits.
- When the house has been extended before and the allowances are less clear.
- When you plan to sell in the next few years.
- When a neighbour might complain to the council.
What do you need to apply?
A location plan, existing and proposed drawings, a description of the works and the fee. We prepare the drawings and the application as part of our planning service.
Can I start building before the certificate is issued?
You can, if the extension genuinely is permitted development, but you take the risk that the council disagrees. We recommend waiting for the certificate, especially where the design is near the limits.
This guide is general information, not legal or professional advice for your property. Rules can change; we check the current position for your address at the survey.