You can normally build single storey, full-width rear extensions to a depth of 4m for detached properties or 3m for other types of houses without planning permission. Single storey extensions are restricted to a height of 4m. If it is within 2m of a boundary the height of the eaves (if it has them), it cannot exceed 3m.
Mulit-storey Rear Extensions to Houses
Extensions of more than one storey cannot be built if:
- there is less than 7m between the extension and the rear boundary;
- the property is in a conservation area.
If one or both of these of true then you will need to either apply for planning permission or only build a single storey.
If a multi-storey extension is allowed the only restriction to the number of storeys is the height of the existing house, which cannot be exceeded. As well as the overall height, the eaves on the extension (if it has any) cannot be higher than those of the existing house or 3m for the parts within 2m of the boundary.
Extensions of more than one storey are restricted to a depth of 3m for all houses.
Restrictions that Apply to Both
There is no longer any restriction for rear elevations that face the highway, unless the rare circumstance has occurred where it has been decided that the back of your house is the principal elevation. Infiniti uses the following definition to decide which side of the house is the principal elevation: “The elevation that is designed to be the main elevation of the property (which will generally front a highway) and includes the most architectural detail (for example gable or bay window details or decorative porches).” Normally this will be what everyone agrees is the front, but if your house is at an angle to the road, on a corner, backs onto a road or if you are at all unsure you should check with the planning department which side of your house forms the principal elevation.
The extension must also conform to the following rules:
- If the rear of the house is stepped, then the profile of the existing building must be retained.
- The exterior materials used must be of a similar appearance to the existing building (not conservatories).
- Any side facing veluxs, dormers or upper-floor windows must be obscure-glazed, and non-opening “unless the parts of the window which can be opened are more than 1.7 metres above the floor of the room in which the window is installed”
- Where the extension has more than one storey, the pitch of its roof must, “so far as practicable”, match the roof pitch of the original house.
- If your house is in a conservation area you cannot clad any part of the exterior of the dwellinghouse with stone, artificial stone, pebble dash, render, timber, plastic or tiles without requiring planning permission.
Flats, Maisonettes and Shops
If your property is a flat or maisonette (including those converted from houses) or a commercial property, such as a shop or public house you will need to apply for planning permission.
If you live in a listed building, you will need listed building consent for any significant works whether internal or external or in the grounds (curtilage) even if you do not require planning permission.
Do I need planning permission?
There is a certain amount of work that you can do to your house without requiring planning permission, known as your permitted development rights. If you want to carry out a project that falls outside of these rules it does not mean that you cannot do it just that you must apply for planning permission first.
Please also note that this information is provided for guidance only. The rules surrounding permitted development are complex and depend on your local council and we will help you decide whether the project requires planning permission or not. You should also be aware that previous planning permissions may have restricted permitted development rights and you should ensure that this is not the case before starting any work.
Please note: Whether or not you need planning permission you are likely to need Building Regulations approval.