In the UK there is a planning resource called “Planning Portal.” It helps with questions about planning permission and offers illustrated diagrams to make things easier to understand. There is a dedicated section for decking. As of November 2017 these are the basic facts:

Putting up decking, or other raised platforms, in your garden is permitted development, not needing an application for planning permission, providing:

  • The decking is no more than 30cm above the ground
  • Together with other extensions, outbuildings etc, the decking or platforms cover no more than 50 per cent of the garden area.
    Please note: The permitted development allowances described here apply to houses and not to:
  • Flats and maisonettes
  • Converted houses or houses created through the permitted development rights to change use
  • Other buildings
  • Areas where there may be a planning condition, Article 4 Direction or other restriction that limits permitted development rights.

The Planning Portal then goes on to discuss building regulations:

Building Regulations should be assumed to apply to every deck structure requiring planning permission. If you are unsure about whether you are required to comply, you may wish to contact your local Building Control body.

As with all building control and building regulations you should contact your local building control department which is operated under the umbrella of your local council.

Information correct as of 20.02.17