Single storey Extension A single-story extension is built onto the back or side of a house. It can be up to four meters tall and up to six or seven meters from the back wall. Keep in mind that if the structure is within two metres of a boundary wall, it can only be three metres tall. Typically used to: · Increase the size of your kitchen · Bathroom on the lower level · Living area on the lower level · Additional storage space · Study/workplace There are also other kinds of extensions to think about. Loft conversions , side extensions, and double-story extensions are all possibilities. As a general rule, if the extension is closer than seven meters to the back boundary, permission is required. A semi-detached house can...