Outside the realm of permitted development, explicit planning consent will be needed before you can build your extension. There are several different types of planning permission. They are not all the same and the application type must match the development being proposed.
The guidelines setting out each application type can change over time and subject to local authority interpretation. Here are the essentials of what you need to know.
Householder consent. Where permitted development is not applicable, a householder application will be needed to alter or enlarge a single house (not flats or maisonettes) including for works to other structures within the property boundary. The property should not be listed or sit within a conservation area.
Outline planning consent. This is not full planning consent but more like getting a decision in principle for a mortgage. Here you ask the local authority to take a view on whether they would generally support a given proposal, before spending time and money on the detailed plans. Then at a later stage (usually within three years) you’d follow up with a reserved matters application which fills out the detail of the proposal.
Reserved matters. Use this application to flesh out the details of an outline application that has previously been granted. The local authority will typically want to see detail around the development’s appearance, scale, layout and access arrangements.
Full planning consent. Where permitted development does not apply, this type of consent brings the content of outline and reserved applications together and asks for all the required information to be submitted on one single (full) application. Full consent is always needed for flats and maisonettes, changes of use, changing the number of dwellings and for any proposed works outside of the property’s garden.
Listed building consent. If your property is listed then you will need this level of consent for alterations.
Lawful Development Certificate. This is an official document that stands to sanctify that a development built under permitted development (PD) has been done so lawfully. Homeowners should always have a lawful development certificate in their hand when building their extension under permitted development, for completeness of paperwork. It will be important for any future insurance claims, re-mortgaging or when selling the property.
Prior approval. Prior approval is conditional approval to develop within the suite of permitted development rights. For residential extensions this is primarily applies to proposals to build larger rear extensions (8 meters for a detached house and 6 meters other types of houses.) The same rules apply as under permitted development but with a twist; your neighbours have 21 days to object to the proposal. If they do not object, prior approval is granted and you carry on and build. If they do object, back to the drawing board.
Removal/variation of conditions. Also known as a section 73 application, this is used to ask the local authority to remove a particular restriction/condition on a planning permission or listed building consent, such as the use of a particular building material for instance.
Approval (discharge) of conditions. Where plans have been approved, but with conditions, an approval of conditions application serves to ‘discharges’ the specified restraints from the granted consent. For example consent, for a roof terrace may have been granted so long as the local authority approved the type of glass used on the balustrade. Upon supplying a sample of the glass to the satisfaction of the Planners, the local authority would discharge the condition from the planning consent, leaving you free to build.
Consent under tree preservation orders. If you plan to remove or work on a tree within the catchment of tree preservation order, you’ll need this specific permission to do so. Moreover if the tree sits in a conservation area and measures at least 75mm in diameter at 1.5m from ground level, then you will need special consent under the proposed works to trees in conservation areas application.
Application for non-material amendments. This application is requited if you wish to make changes to already-approved plans.
Conservation areas. If you live in a conservation area, the type of application required will need thought. In the absence of an article 4 direction, permitted development rights still exist although might be curtailed. So you could still apply for your extension under permitted development but the application would need to demonstrate how the proposed scheme would preserve or enhance aesthetic of the area. If you live in a conservation area it is best to engage the local authority early and get a steer on the most suitable way forward.
If the scheme involves demolishing a structure more than 115m3, works to enclosures adjacent to highways more than 1 meter high, or 2 meters elsewhere, then explicit planning consent for relevant demolition in a conservation area will be required.
So as far as residential extensions are concerned, the main types of planning consent you will be concerned with are threefold. (1) A certificate of lawful development is there to sanctify a permitted development application. A lot of residential extensions fall under this category. (2) For extensions that do not meet permitted development criteria, the householder application will likely be necessary. (3) If your home is a listed building or is a flat or maisonette, then a full planning application will be required.