This would not require permission provided:
- The extension is not more than 3 metres deep. If a first-floor extension is being added to an existing ground-floor extension, both the ground-floor and first-floor elements must not be more than 3 metres deep. Thus, for example, you cannot add a 3-metre deep first-floor extension to an existing 4-metre deep ground-floor extension.
- The extension should be at least 7 metres from the rear boundary measured at the closest point.
- If any of the extension is within 2 metres of any boundary, the eaves should be no more than 3 metres high. This means that as the eaves of any first-floor extension would be more than 3 metres high, no part of a two-storey extension, even if it is just a ground-floor element should be within 2 metres of any boundary or planning permission would be required.
- Unless it is a conservatory it is built using external materials similar in appearance to those on the existing house