Home extensions generally need you to obtain a permit before you can go forward with the job. Especially, for a new extension to the old plan of your house, it is mandatory to seek a permit from the local authority. Standards set out in the 'Building Regulations' need to be followed and met. This is precisely what is checked by the authority when you present them your new home extensions plan. They inspect the plan and confirm it meets the building regulation standards. Upon the receipt of the planning permission you will then need to apply for the Building Regulations. It is necessary to obtain the planning permission before proceeding with the further actions.