How high can I build an extension without permission?
The planning rules covering extensions are explained in this section on the Planning Portal.
You may also find our extensions mini guides useful, they illustrate visually what is covered in our text guidance:
If, after using our site guidance, you have further questions about a particular aspect of planning permission you should contact your local planning authority, usually your council. Our Service Desk aren’t planning experts so you will need to talk to your local authority planning team.