Side extensions

A single-storey side extension on a house in England is usually permitted development. It must be no wider than half the original house and no higher than 4m. Anything taller, or on two floors, needs planning permission.

The limits

	Limit
Storeys	One
Height	4m
Width	Half the width of the original house
Eaves within 2m of a boundary	3m

• The width of the original house is measured at its widest point.
• No higher than the existing roof, and eaves no higher than the existing eaves.
• Not beyond a side wall that faces a road, which on a corner plot rules out that side.
• No balconies, verandas or raised platforms.
• Together with other buildings, no more than half the garden and grounds.
• Materials similar in appearance to the house.

Wrap-around extensions

An extension that fills the corner between the side and the rear must meet both sets of rules. It stays single storey, no higher than 4m, and no wider than half the house, and its depth is limited as for a rear extension.

Earlier extensions count. If a new extension joins an old one, the two together must stay within these limits.

When permission is needed

• Two storeys, or taller than 4m.
• Wider than half the original house.
• The house is a flat or maisonette.
• Conservation areas, National Parks, National Landscapes, the Broads and World Heritage Sites: no side extensions at all.
• The council has an Article 4 direction removing extension rights on your street.
• A condition on an earlier permission has removed the rights.

For the wider rules, see permitted development rights explained.

Source: The Town and Country Planning (General Permitted Development) (England) Order 2015, Schedule 2 Part 1, legislation.gov.uk; Permitted development rights for householders, technical guidance, Ministry of Housing, Communities and Local Government.