Increased Extension Size Allowances Made Permanent

The number of people choosing to add an extension onto their property is set to continue to grow thanks to new government reform on Permitted Development building allowances.

By Larry Bohan on 3 Jul 2019

The length at which detached homes can extend without having to apply for planning permission has now been permanently doubled from 4 metres to 8 metres. The allowance for semi-detached and terraced homes has also doubled from 3 metres to 6 metres. 

The changes in regulation have been trialled for the last six years, a period that has seen a marked increase in the number of extensions being built. The new law changes will be music to the ears of both developers and homeowners. 

Developers will welcome the inevitable speed up of projects, while homeowners will be able to create bigger, brighter open plan spaces with enough room for the whole family to thrive in.

Kit Malthouse, MP and Housing minister said: "Through relaxing planning restrictions, these measures will help families extend their properties without battling through time-consuming red tape.”

All extension proposals will still need to be disclosed to the relevant Local Planning Authority. Nearly all previous regs on extensions, such as height and material restrictions, still apply. A full list can be found on the Planning Portal website.

Permitted Development: What has Changed?

Detached Houses- Single storey rear extensions must not extend beyond the rear wall of the original house by more than 4 metres.

Other Dwelling Houses- Single storey rear extensions must not extend beyond the rear wall of the original house by more than 3 metres.

Detached Houses- Single storey rear extensions must not extend beyond the rear wall of the original house by more than 8 metres.

Other Dwelling Houses- Single storey rear extensions must not extend beyond the rear wall of the original house by more than 6 metres.

For more extension ideas and advice, get clued-up and inspired by some of our other articles.

Single Storey Extension Guide

• Home Improvement Ideas- Flat Roof Extensions

• Home Improvement Ideas- Lantern Roof Extensions