Permitted Development essentially allows someone to make alterations and additions to their buildings without needing Planning Permission. A set of criteria and typical alterations is considered being ‘pre-approved’ by planning. Typically this includes minor porches, satellite dishes, flues, certain rooflights etc. However, crucially, some fairly significant extensions also fall under the Permitted Development (PD) criteria.
There is an extended array of diagrams and information on the Planning Portal website that go into these further and more accurately than this overview. The most useful document, albeit fairly cumbersome to read, is the technical guidance document that goes into more detail on each of the main criteria.
Generally speaking a modest single storey rear (not projecting out to the side) extension below 4m in total height and 2.5m at the eaves is likely to be considered PD, and can be built without full planning permission. It should be built from similar materials to the main house. There are some other limiting criteria but usually a rear extension of this sort can be achieved under PD.
A basic loft conversion can also fall under PD provided you meet the qualifying criteria.
TSA Ltd always recommends seeking a Certificate of Lawful Use from the council. It can take as long as applying for Planning Permission, but the council can only comment on if it meets the PD criteria, not other factors that usually influence a Planning application decision. The Certificate of Lawful Use essentially is a piece of paper stating that the project does not need planning permission. It is a good document to have should any issues arise, and solicitors will ask for one when you come to sell up.
Permitted Development rights can be removed by the council using special powers (usually to limit HMO conversions or through previous planning applications to limit further extensions) and PD is significantly reduced or removed if you live on/in ‘Designated Land’ (National Parks, World Heritage Sites etc), a Conservation Area or in a Listed Building.
Some examples of TSA projects that were allowable under Permitted Development are below.