Prior approval for extensions and conversions

The government has changed Permitted Development rights so that householders can build larger extensions. However before starting their project they must gain Prior Approval from the council.

The increase is from 3 metres to 6 metres for a terraced or semi-detached property, and 8 metres for a detached property.

Completion is taken to be practical completion (walls, roof, doors and windows completed and the building watertight).

The new Prior Approval procedure requires the developer to provide some basic information about a proposed extension. It also involves a process of consultation with immediate neighbours. This process lasts 42 days.

If you gain Prior Approval it does not necessarily mean your development is lawful, as there are other permitted development rules you must comply with. Combining the extension with other developments also might not be allowed, even if those developments have permission separately. This is because the developments combined may change the circumstances, making it unlawful. The council recommends you obtain a Certificate of Proposed Lawful Development.

Notes and application form

Postal applications can be sent to the contact details at the bottom of this page.

Please note, smaller extensions, typically 3 metres or under for semi detached houses or 4 metres for detached houses do not need prior approval, but are subject to all relevant permitted development restrictions.

Planning and Building Control Team

Please use the details below for all enquiries regarding planning consent and building control, including any change of use or change to the outside appearance.

Address: London Borough of Harrow
Planning and Building Control
PO Box 1358

Telephone: 020 8901 2650