Homes with an extension – What should you check before buying?

A property that has been extended or modified might give you the space you are looking for, but there are a number of checks you should make before making your offer.

Has the house been extended?

This may not be obvious and some apparent extensions may have been included in the original build – such as 3rd storey bedrooms in the attic space, or garden rooms and conservatories.

If there is an extension, consider how large it is and whether it takes up significant garden space.

  • Does it extend to the neighbouring boundary?
  • Is there more than one extension?
  • If the roof has dormer window, how do they align with the existing roofline?

Does the extension count as ‘permitted development’ or did it require planning permission?

A permitted development (PD) is one where permission is deemed to be granted without having to make an application for planning permission. It generally includes extensions to the rear or side of a property, which are less than 15% of the original volume of the house (10% if part of a terrace) and do not take up more than 50% of the garden. Conservatories or porches are the most common form of permitted development.

If an extension is greater than 115 cubic metres in volume it will have required planning permission.

Planning permission is also necessary for extensions that:

  • Extend beyond dimensions allowed for PD (e.g. more than 3m for a 2-storey extension
  • Are taller than original roof height
  • Are additional extensions, which added to other extensions exceed the 15% limit.

Properties in conservation areas or with listed building status always require PP for alterations.

Ask the owner for evidence to support any work that has been done, such as planning approval or a Lawful Development Certificate, provided by the local authority to prove the extension meets planning control requirements as a permitted development.

Is there a certificate of compliance to building regulations?

Most extensions (apart from porches and conservatories) require a certificate of compliance with building regulations. This is generally the responsibility of the contractor who carried out the work. The certificate should be given to the property owner and the local authority informed that the work has been competed according to the required standards.

Buyer beware

Be aware that enforcement notices can be served against any property owner if an extension has been built that breaches the law – even if the person was not the owner when the work was carried out.

A property owner might unwittingly breach planning regulations for example by constructing a conservatory when a house has already been extended or converting a loft into a bedroom without checking building regulations

Failing to address the breaches can lead to fines or even imprisonment, so check carefully.

If there is no documentation, but the work was completed over 4 years ago and no action has been taken by the local authority it will not be able to now do so.

For further information the exact legislation can be found in the Town and Country Planning (General Permitted Development) Order 1995 as amended by the Town and Country Planning (General Permitted Development) (Amendment) (No. 2) (England) Order 2008.