This is separate from the planning process and again, it may not be required depending upon the type of change that you are planning. Building Regulations Approval exists to ensure that any work that is carried out, is done so to strict quality and safety standards.
The process involves submitting detailed construction plans with notes of the work involved, explaining how the work will actually be done. The local authority will check the plans to make sure they will meet all the current building regulations. They may suggest some amendments to the notes/plans or may ask for some further information to make sure the contractor is instructed to do work to that meets current regulations.
It’s important to note that there is a different requirement for the detail level of plans being submitted for either planning, or building regulations approval as they are two separate processes. My fees generally include BOTH sets of drawings unless otherwise stated or discussed.
The building regulation fee is based on the size of the new extension or alterations. The fee payable when the plans are submitted will be £160.00. Approval can take up to 5 weeks.
Note that when you start the work there will also be a further ‘one off’ fee called the inspection fee. The council will send you an invoice for this.
As a guide for a medium sized single storey extension the inspection fee would be £368.00.
For a medium sized two storey extension the inspection fee would be £401.00 at current rates.
The Planning Portal also includes a section dedicated to Building Regulations.