Planning Your Underground Extension
Permits and requirements
When you are altering, extending or demolishing a basement you must comply with a wide range of laws. These may require you to seek different types of permission, including:
Planning permission, except in circumstances where it may be permitted development
Listed building consent (if the building is listed)
Structural impact assessment or report (if the building is listed or of merit to the townscape)
Building regulations approval
Highway licences – Many of these must be applied for before starting work and include skip, scaffolding, hoarding and building material licences, parking suspensions and trader parking permits
Temporary traffic orders (closing pavements, road space and bus stops)
Party wall agreement if work is within three or six metres of adjoining land
Notifying the council and neighbours if the work will involve environmental health risks including noise, vibration, dust, contaminating land or changes habitable accommodation standards
Freeholder consent – This is always required, including before submitting a planning application
Utilities permission – This includes water suppliers and transport companies such as Network Rail
In addition to these circumstantial requirements all basement developers must prepare and submit a statement of how the construction will be managed as well as sign up to a Considerate Construction Scheme.
What are the potential issues?
Proposing basement works can throw up unexpected issues. Here are just a few of the common design problems that you should be aware of while planning your basement project:
Inappropriately large extensions – This is as true below ground as it is above ground!
Trees and roots – Be aware of trees on or near your site and the space their roots need to be protected, as encroaching this space may categorise your basement as overdevelopment
Gardens – Proposed basements should not take up more than half of a front and/or back garden as they may impact biodiversity
Rain and drainage – Any development should provide enough planted material to absorb rainwater adequately
Basements as accommodation – Basements used as housing must be of high quality and provide a good standard of sunlight, outlook and privacy