When the proposed work falls outside the rules for permitted development then planning permission must be obtained. Planning permission allows for the development of land and existing properties it is usually granted by the local planning authority, which is part of the local council.
A planning application involves the production of scale drawings of the existing property and of the proposed development. It also involves various forms and certificates covering the detail of the work, environmental issues and other matters.
Following submission of the application, there may be modifications required by the planning officer prior to a recommendation being made by the planning officer to the planning committee. At this stage, the application will be rejected, accepted or accepted with planning conditions.
These conditions are very important and must not be breached.