You need to apply for Building Regulations before you start any work on renovation of a thermal element.
A thermal element is something that separates a heated or air-conditioned space from the outside. This could be a wall, floor or roof (but doesn’t include windows, doors or roof-lights).
If 25% or more of a thermal element is being replaced or renovated, you will be expected to improve the thermal performance of that element. This will usually be achieved by adding insulation.
If you need help or advice please contact Powys Building Control using the contact details on this page.
Your local builders’ merchant may also be able to give you advice on the most economical solutions.
If you don’t have your work authorised by Building Control, this may cause problems when the property is sold. In some cases, it could lead to prosecution.