Permitted Development is Not Always Straightforward
Under the new rules, the ‘original’ (as it stood in or prior to 1948) rear wall of a detached home can be extended by up to 8m in depth with a single storey extension; this is reduced to 6m if you are extending a semi-detached home or terrace. If your proposed new extension will be within 3m of a boundary, then the eaves height is limited to 2m under Permitted Development.
If you hope to build a two storey extension (no higher than the house), this can project up to 3m from the original rear wall, so long as it is at least 7m from the rear boundary. It’s also important to note that no extension can project beyond or be added to what is deemed to be the front of the house or an elevation which affronts the highway. A side extension cannot make up more than half your house’s width.
Furthermore, with the exception of conservatories, new extensions must be built of materials ‘similar in appearance’ and with the same roof pitch as the main house. So while Permitted Development rights are beneficial, there’s a lot to consider before extending.
Is there anything else I can do under my Permitted Development rights?
Prior to the new legislation, volume limitations were applied to the entire house — so if you were extending, you were unlikely to be able to convert your loft under Permitted Development rights as well. The good news is that the latter has now been separated out, allowing you to undertake both without one restricting the other. So when you are extending your home, you can also convert your loft into a bedroom or extra living space by up to 50m³ in a detached house, or by 40m³ within any other home.