Planning Permission Frequently Asked Questions
Can I build an extension?
Small scale domestic extensions, including conservatories, do not require planning permission if the extension is to the rear of the house and comply with the following:
• the original floor area of the house is not increased by more than 40 square metres. It is important to note that where the house has been extended before, the floor area of the extension you are now proposing and the floor area of any previous extension, including those for which you got planning permission, cannot exceed 40 square metres;
• for terraced or semi-detached houses, the floor area of any extension above ground level does not exceed 12 square metres, this includes any previous extensions carried out;
• any extension above ground floor level is at least 2m from any boundary;
• any extension does not exceed the height of the house;
• any extension does not reduce the area of private open space, reserved for the occupants of the house, to less than 25 square metres.
There are also rules about the height allowed in such an extension. These are that:
• if the rear wall of the house does not include a gable, the height of the walls of the extension must not exceed the height of the rear wall of the house;
• if the rear wall of the existing house has a gable, the walls of the extension (excluding any gable being built as part of the extension) shall not be higher than the side walls of the 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;
• a gable is the upper part of a wall (normally triangular), between the sloping ends of a pitched roof.
There are also rules about the required distances between windows in extensions, the facing boundary of the adjoining property and the use of the roof of the extension. These are;
• any windows proposed at ground floor level as part of an extension should not be less than 1 metre from the boundary they face;
• any windows proposed at above ground level should be not less than 11 metres from the boundary they face;
• the roof of any such extension should not be used as a balcony or roof garden.