The development guides for loft conversions can be quite confusing, so we’re enclosing all the information you need to know in this handy blog post.

Before we begin, here’s the definitions of terms we mention:

‘Original House’ – Refers to the house as it was first built, or as it stood on the 1 st of July 1948 (if it was build before that date). Although you might not have built an extension to the house, a previous owner may have done so.
‘Designated Land’ – This land includes national parks and the Broads, Areas of Outstanding Natural Beauty, World Heritage Sites and conservation areas.

So let’s get started!

A loft conversion for your house is considered to be permitted development which does not require an application for planning permission, that is provided certain limits and conditions are met. We have outlined these below:

1. Loft conversions are not permitted development for houses on designated land.

2. In order to be permitted development, additional roof space created must not exceed the following volume allowances: 50 cubic metres for detached and semi-detached houses and 40 cubic metres for terraced houses.

3. You need to bear in mind that any previous roof space additions need to be included within this volume allowance. So for example if there was already 20 cubic meters installed on your roof, you are only permitted 20 more if you’re in a terraced house. You must remember that while you may not have created that additional space, a previous owner might have.

4. An extension beyond the plane of existing roof slope of the principal elevation that fronts a highway is not a permitted development.

5. No part of the extension is to be higher than the highest part of the existing roof.

6. Materials are to be in similar appearance to the existing house.

7. Any side-facing windows must be obscure glazed and non-opening unless the parts which can be opened are more than 1.7m above the floor of the room in which it’s installed.

8. Any verandas, raised platforms or balconies are not permitted development.

9. Roof extensions – apart from hip to gable ones – are to be set back as far as practicable, at least 20cm from the original eaves. This 20cm distance is measured along the roof plane. If you would like a detailed explanation of how this is done, you can refer to pages 35-36 of the ‘Permitted development for householders – technical guidance’ PDF.

Bats and Other Species

Work on a loft or roof may affect bats. You need to consider protected species when you are planning work of this kind. It is possible that a survey may be needed to figure out what animals reside in your area, and if bats are in fact using the building, you may require a license to continue. You can contact Natural England for more guidance on this. If you know already that you may have bats, then go here for information specifically regarding them.

You Should Note

The permitted development allowances that we’ve described here apply to houses, but not maisonettes, flats or other buildings. You should of course check with your Local Planning Authority to see if permitted development rights apply to you as they may have been removed by what are known as Article 4 directions. It’s important that when planning work you should read all of the advice on the Planning Portal under ‘Your responsibilities – Other considerations before you start work’.

Building Regulations

To convert your loft or attic into a liveable space, you will need building regulations approval. The regulations are applied to ensure:

  • The stability of the structure (including the existing roof) is not endangered
  • The structural integrity of the new floor is sufficient
  • Safely designed stairs to the new floor
  • Safe escape from fire

Reasonable sound insulation between the rooms below and the new conversion. It is recommended that you contact Building Control to discuss your proposal and for more advice. You must also find out whether work you intend to carry out falls within The Party Wall etc Act 1996, which we have written about here on our blog.