The need for planning permission for development depends on their nature and scale. Government defines by statutory instrument which categories of development needed to obtain express planning permission and which are deemed “permitted development”. 'Permitted development' rights grant deemed planning permission for certain types of development provided you meet certain conditions. What is and is not considered permitted development is set out in a piece of legislation known as the General Permitted Development Order (GPDO).
The GPDO is a long and complex document in 40 parts and is constantly being amended by new legislation. A copy of the Town and Country Planning (General Permitted Development) Order 1995 (as amended) can be viewed and downloaded by clicking on the link above.
Exceptionally, permitted development rights may have been withdrawn for instance in a Conservation Area or in relation to a quarry or landfill site. In those circumstances, a planning application may be necessary.
This page offers a basic summary of permitted development rights for developments that would be dealt with by the County Council's Development Control Team (i.e. Minerals and Waste related proposals and developments by the County Council outside of the National Parks). For a good overview of permitted development rights for householders please see the Lake District National Park's Web-Pages.
If you require further clarification as to whether proposed development requires permission please contact the relevant planning authority.