I would like to build an extension to my house but I am unsure if I need to apply for planning permission. I understand some extensions may not require planning permission provided they are under a particular size, is this correct? Are there any other restrictions?
Whether the proposed extension to your property requires planning permission or not will depend on a number of factors. Generally, small domestic extensions will not require planning permission if it does not exceed 40 square metres in size. However, any previous extension must also be considered so that the combined area of all extensions may not exceed 40 square metres.
For terraced or semi-detached houses, the floor area of any extension above ground level may not exceed 12 square metres. Also, the extension may not exceed the height of the house and the extension may not reduce the area of private open space to less than 25 square metres.
Specific rules also apply regarding height. For example, if the rear wall of your house does not include a gable, the height of the walls of the extension must not exceed the height of the rear wall of your house. If the rear wall of your house has a gable, the walls of the extension shall not be higher than the side walls of your house. In the case of a flat roofed extension, the height of the highest part of the roof may not exceed the height of the eaves or parapet. In any other case, no part of the new roof may exceed the highest part of the roof of the house.
It is strongly advisable to speak with your architect or engineer regarding your specific plans prior to commencing works. Your Local Authority can take action if a development does not have the required permission, or where terms of permission have not been met. The Local Authority may require you to take whatever steps they deem necessary in order to regularise the development.