Home extensions will not normally require planning permission as they are considered permitted developments. However, there are some exceptions.

Basic Rules To Adhere To

For every type of extension there are a few rules that need to be adhered to. Any extension shouldn’t take up over half of the house’s original size, and the extension must complement the overall look of the property. Things such as balconies and verandas are not permitted, along with any type of raised platform. No extension can be higher than the house’s roof either, with the eaves and the ridge both being taken into account when determining the roof’s height. When any extension is within a couple of metres of a boundary, then the eaves should be no more than three metres in height. While, when facing a highway, no extension should be protruding from the main or side elevations respectively.

There are specific rules, too, for extensions, concerning where the extension is intended to be, or concerning its size. These include single storey rear extensions, side extensions and extensions above a single storey.

Rear Extensions Regarding Single Storey Buildings

For semi-detached homes, any extension is not permitted to go beyond three metres of the property’s existing wall. For detached properties then any extension shouldn’t go beyond four metres. Any extension also can’t be over four metres high.

Side Extensions

A side extension can only be carried out on a single storey building. It should not exceed four metres in height, and, in terms of width, the extension should be no more than 50% of the width of the original size of the house.

Extensions Above A Single Storey

An extension should be over three metres past the original house’s wall. The extension mustn’t exceed a distance of seven metres near to the house’s rear boundary. The roof pitch of the extension should be greater in height than that of the original house. Upper floor windows, which face the side, need to be obscure-glazed and a minimum distance of 1.7 metres above the floor.

Rules For Properties In Protected Areas

When extensions are planned for properties in protected areas, i.e. World Heritage Sites and Areas of Outstanding Natural Beauty, then no side extensions are allowed, or any cladding of the outside of the property or an extension. Also not allowed in these areas are rear extensions of more than a single storey.