Basement extensions

Basement extensions are an increasingly common form of development in Westminster.

The council formally adopted a new policy on basements (CM 28.1 Basement Development) in July 2016 as a revision to the Westminster City Plan. This policy requires applicants to comply with the council’s new Code of Construction Practice when undertaking their development to ensure the environmental impact of construction works is monitored, controlled and managed. 

Find out more about submitting an application including forms and checklists.

Adopted Supplementary Planning Document (SPD)

We previously adopted guidance on this issue in the 'Basement Development in Westminster Supplementary Planning Document' (SPD), which was adopted by a Cabinet Member decision on 20 October 2014. This SPD doesn't include new planning policy but supports the implementation of adopted policies in the council’s development plan and in particular provides guidance on:

  • when a planning application is required and what information you will need to submit (section 3 to 4)
  • the adopted policy framework and how planning applications for basement development will be assessed in relation to this (section 2 and 6)

It also includes advice on other regimes used to control basement development such as highways and building control, as well as links to useful sources of information and contacts (section 7 and appendices).

The guidance note and associated documents can be downloaded below:


Last updated: 24 January 2017
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