A single-storey side would not require permission provided:
- The extension would not be between the house and a highway, i.e. if the house is on a corner plot and an extension is proposed on the side facing the highway
- All parts of the extension would be lower than the highest part of the roof of the original house (this would normally only be an issue when a bungalow was to be extended)
- The eaves of the extension would be lower than the eaves of the original house (this would normally only be an issue when a bungalow was to be extended)
- The extension would be no more than 4 metres high
- If the extension is within 2 metres of the boundary the eaves would be less than 3 metres high
- The extension would exceed half the width of the original dwelling. On a detached house, provided the plot can accommodate them, it is possible to build a “half-width” single-storey extension on each side
- Unless it is a conservatory it is built using external materials similar in appearance to those on the existing house