House Extension Rules in 2020

To build the extension you have always wanted, you need to realize and learn the rules concerning your building. This should not discourage you from building the extension, though. If you are planning on building an extension, you only need to know some basic rules about your building. We summarized various simple key factors that you need to review when it comes to building an extension for your single-storey, two-storey, side, and rear extensions. SINGLE-STOREY EXTENSION RULES

In single-storey extension projects, only half of the land occupying around the original building can be covered with an extension. This area can include a shed or outbuilding, too.

If you want to build an extension out toward the main road, it requires planning permission in single-storey extension projects. Therefore, the extension cannot be forward of the side elevation or side elevation fronting a highway.

The materials used when the single-storey extension is built must comply with the original building’s current look. However, a conservatory constitutes an exception.

If your property is on designated land, then exterior cladding will not be allowed for the single-storey extension.

For a single-storey rear extension, the extension cannot go beyond the back wall of the original building by more than 4 metres.

Any single-storey extension cannot exceed 4 metres in height.


If you plan to build an extension for a building that has more than one storey, going past the back wall of the original building by over 3 metres is not allowed.

The maximum height of the extension’s eaves needs to be 3 metres if you are within 2 metres of the boundary.

The ridge and eaves height cannot be taller than the existing property.

The extension you plan to build needs to be a minimum of 7 metres away from the rear boundaries.

The roof pitch needs to match or be as close to the existing building as possible.

Any raised platforms, verandas, and balconies require planning permission.

The upper-floor windows in the roof slope or wall on the side elevation need to be obscure-glazed and they can not be opened.

On any designated land, a two-storey extension is not covered by permitted development rights.

The exterior of the extension must use similar-looking materials to those of the existing property.


A single-storey side extension must not exceed 4 metres in height and cannot have a width of more than half of the original property.

Side extensions are not permitted on designated land.


A single-storey rear extension can not go beyond the rear wall of the original property by no more than 4 metres.

A single-storey extension to the rear can not be more than 4 metres.

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