Permitted Development essentially allows someone to make alterations and additions to their buildings without needing Planning Permission. A set of criteria and some typical alterations are considered as being ‘pre-approved’ by planning. Typically this includes minor porches, satellite dishes, flues, certain rooflights etc. However, crucially, some fairly significant extensions and changes of use (For example some agricultural barns can be changed to a dwelling under Class Q of the Permitted Development Order) 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 for homeowner alterations, albeit fairly cumbersome to read, is the technical guidance document that goes into more detail on each of the main criteria.
The planning jungle website has useful information, but it has such a vast database of case law the website is a bit ‘functional’ and can become a bit overwhelming, most of the info is also only available to members who pay an annual fee. However, the most useful commentary on homeowner PD is the visual guide, of which there is an abridged free version for non-members. It is a quick and easy reference for additional info to those on the Planning Portal site.
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 and are not a ‘designated’ building or land (Listed, Conservation Area plus others etc).
TSA Ltd always recommends seeking a Certificate of Lawful Use from the council for anything that is larger than a basic porch. It can take as long as applying for Planning Permission, but the council can only comment on if it meets the PD criteria or not, and not other factors that usually influence a Planning application decision such as appearance, scale, overlooking etc. The Certificate of Lawful Use essentially is a piece of paper stating that the project does not need planning permission and is within the PD criteria. It is a good risk-reducing 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 called an ‘Article 4 Direction’ (typically to limit HMO conversions, changes of windows etc 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. A Conservation Area to have the full weight it deserves however needs an Article 4 Direction to prevent people changing windows to PVC and taking down low boundary walls etc. otherwise some of these can be done still while within a Conservation Area, but do check (and consider the wider visual impact) before carrying out any such work. Permitted Development is not possible on a Listed Building (even if included in the Listed by virtue of being within the curtilage of a Listed Building) or flats.
During design development we can determine whether it will fall under the PD criteria or need to trigger a planning application. Bizarrely some projects (particularly loft conversions) can be built larger using PD rights than would be permissible under Planning as the local design guides will be more restrictive than the basic PD criteria. Some examples of TSA projects that were allowable under Permitted Development are below.