Permitted development rules for house extensions in England

Permitted development lets you extend a house without applying for planning permission, as long as the extension stays within set limits. Here are the main rules for extensions (Class A of the General Permitted Development Order), and a free way to check your own design.

Rules for every extension

• Extensions and other buildings must not cover more than half the land around the original house (as it was built, or as it stood on 1 July 1948).
• No extension forward of the principal elevation (usually the front), or of a side wall that faces a road.
• No higher than the highest part of the existing roof, and the eaves no higher than the existing eaves.
• Within 2 metres of a boundary, the eaves can be no higher than 3 metres.
• Materials should look similar to the existing house.
• No verandas, balconies or raised platforms.

Single-storey rear extensions

Depth is measured from the rear wall of the original house. The larger home extension scheme needs you to notify the council first, and neighbours can comment.

Two-storey (or more) rear extensions

• No more than 3 metres deep from the rear wall of the original house.
• At least 7 metres from the rear boundary.
• The roof pitch should match the existing house as far as practical.
• Upper-floor windows in a side wall must be obscure-glazed and fixed shut below 1.7 metres from the floor.

Side extensions

• Single storey only, no more than 4 metres high.
• No wider than half the width of the original house.
• A two-storey side extension always needs planning permission.

Front extensions

An extension that goes beyond the principal elevation is not permitted development and needs planning permission. A small porch has its own, separate allowance.

Designated land

In conservation areas, National Parks, National Landscapes (formerly AONBs), the Broads and World Heritage Sites, side extensions and extensions of more than one storey at the rear are not permitted development, and walls can't be clad in stone, render, timber, plastic or tiles.

Check your own design

Extension Plans checks each extension in your drawing against these rules automatically — side, rear or front, depth, height, eaves, the distance to the boundary and how much of the garden is covered — and tells you which rule fails and why. Upload your floor plan and it builds the house for you.