House Extensions & Planning Permission

Building a new side return or doing a loft conversions? If you're planning a house extension you'll want to double check you have the necessary planning permission, otherwise you could be forced to knock it all down!

By MyLegalAdviser - Last Updated January 2018

If you want to build something new, make major alterations to your property or change what your property is used for, you’ll generally need to get planning permission.

To help you understand the key issues when considering planning permission, we've put together a guide on what you need to know about planning permission, when you might need it and what happens if you don't get it.

When is planning permission (usually) required?

Whilst it isn’t possible to give an exhaustive list of the circumstances in which planning permission will be required, the general rule of thumb is that most new building projects, any significant alterations to a property and changing what a property is used for, will generally require planning permission.

Where planning permission is required, homeowners will need to bear in mind that some planning authorities are much stricter than others. Certain other factors, such as whether your property is listed or in a conservation area, may also determine whether your application for planning permission is likely to be granted.

Permitted development

Some works (e.g. a loft conversion or side return) may be allowable under permitted development. Permitted development means that, whilst planning permission is still required, it is automatically given.

Whether the works will fall under permitted development will usually come down to the extent of the changes you want to make. The rules are quite complex but, generally, an addition or alteration will be permitted development where it is at the side or rear of the house (not facing onto a road) and is less than 15% (10% for terraced houses) of the size of the original volume of the property. It should be borne in mind that this rule is cumulative. So, if an extension has already been built which is, for example, 5% of the size of the original house, any new extension must be no more than 10% (5% for terraced houses) of the original house.

A loft conversion for your house is considered to be permitted development where:

  • less than 40 cubic metres of additional roof space is added for a terraced house;
  • less than 50 cubic metres of additional roof space is added for semi-detached or detached houses;
  • there is o extension beyond the plane of the existing roof slope of the principal elevation that fronts the highway;
  • no extension is higher than the highest part of the roof;
  • the materials are similar to those used on the house already;
  • the extension is set back, where possible, at least 20cm from the original eaves;
  • the extension doesn't overhang the outer face of the wall of the original house;
  • side-facing windows are obscure-glazed and any opening is 1.7m above the floor;
  • no veranda, balcony or raised platform is added; and
  • the house isn't in a designated area.

What happens if I don't get planning permission?

You should always check if you need planning permission before you make any changes as, if permission isn’t granted and you needed it, you could be made by the council to put things back to the way they were...and, to add insult to injury, you'll have to pay for as well!

Where planning permission hasn't been obtained and the breach was a number of years ago, it may be possible to obtain a Certificate of Lawful Existing Use or Development. A Certificate of Lawful Existing Use or Development isn't planning permission, rather it is confirmation by a local authority that no future enforcement action will be taken by them in respect of the breach.

A Certificate of Lawful Existing Use or Development can generally be obtained where:

  • there has been a continuous use of land or buildings (other than a dwelling) for more than 10 years;
  • a condition or limitation on a planning permission has not been complied with for more than 10 years;
  • building or other operations have been completed for more than 4 years; or
  • a building (not land) has been used as a dwelling for more than 4 years.

Applying for a Certificate of Lawful Existing Use or Development requires completing an application with evidence that the breach existed before the required time frame (i.e. 4 or 10 years) and has been continuous since then.

If you're considering applying for a Certificate, you should be aware that in April 2012 the Government introduced new law regarding 'deliberate concealment'. If a Local Planning Authority considers a development has been deliberately concealed they can apply for an order from the Court to ‘immediately’ rectify the breach (e.g. to demolish an unauthorised extension).

House extension planning

DEMOLITION MAN: make sure you have the permissions you need before you give your builders the go ahead, otherwise you might be forced to knock down your house extension!

It is also worth bearing in mind that the grant of a Certificate applies only to the lawfulness of development in accordance with planning legislation. It does not remove the need to comply with any other legal requirements such as The Building Regulations 2010, the Wildlife and Countryside Act 1981 or the Planning (Listed Buildings and Conservation Areas) Act 1990 or other licensing or permitting schemes.

Finally, it may not be possible to apply for a Certificate of Lawful Existing Use or Development where your property is a listed building or in a conservation area. Lawful Development is a complex area and it's well worth speaking to a planning specialist prior to making an application, otherwise you could fail to meet the criteria and find yourself faced with an enforcement order. For more on Lawful Development Certificates, see the lawful development guide.

What about buying a property which doesn't have planning permission

If you’re buying a property and you can see work has been done to it, make sure your conveyancer checks (which they should do anyway) whether all the necessary permissions were obtained before you complete the purchase. If they weren’t then you could be on the hook to put things back to the way they were.

If you’re dead set on the property, even though it’s missing planning permission, you could consider asking for a Certificate of Lawful Existing Use or Development where the requirements are met (see above) or taking out planning permission indemnity insurance. Planning permission indemnity insurance is a policy which will pay for the cost of putting things back to the way they were if the council serves you with an enforcement notice. However, there are a number of things you need to be aware of (like not disclosing the breach to the local council) and we suggest discussing how these policies work with your solicitor before taking one out.

Will it be difficult so sell a property without any necessary planning permission?

The short answer is, probably. If you make changes to your property without getting planning permission and then try to sell it, you may find it very difficult to sell as potential buyers won’t want to risk having to face an enforcement order (i.e. having to put things back to the way they were) after they move in.

If the work was done some time ago, consider whether you may be able to apply for a Certificate of Lawful Existing Use or Development (see above). If not, you may need to reduce the price and/or offer to pay for planning permission indemnity insurance. Be careful about tipping the council off though, as this could mean a buyer isn't able to obtain an indemnity policy.

Appealing a planning decision

If you’ve been denied the planning permission you’ve requested, it’s possible to appeal the decision. Before you do so, however, it’s worth speaking to a planning permission specialist who can advise you of your chances of a successful appeal, otherwise you may well be wasting your time and money on a lost cause.

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