Permitted development rights are a national grant of planning permission which allow certain building works and changes of use to be carried out without having to make a planning application.
Permitted development rights are set out in The Town and Country Planning (General Permitted Development) (England) Order 2015
Permitted development rights which apply to many common projects for houses do not apply to flats, maisonettes or other buildings. There are also some restrictions to permitted development rights within conservation areas and there are also different requirements if the property is a statutorily listed building.
Article 4 Directions remove specific permitted development rights as set out in the Town and Country Planning (General Permitted Development) Order 1995 (as amended). This will mean that you have to submit a planning application for work which otherwise would not need one.