Basement Review Draft policy and other measures for public consultation

Executive Summary


Many residents have expressed concern about basements, very largely during the construction phase, and in relation to the impacts on adjacent properties.

The current planning approach has been under review. This paper sets out the main proposals of that review.

The matter is complex, however, as there are a number of regulatory regimes that basements must fulfil. Planning cannot require matters to be dealt with that come under those different regimes – particularly in relation to structure.


Current Situation

The Council's approach towards basement development is set out in the Core Strategy (2010)[1] as well as a supplementary planning document (SPD)[2] , adopted in 2009.

In summary, it allows basements, up to 85% of the gardens, without restrictions on the depth of basements. Controls in relation to construction traffic, noise etc are sought, but often by condition, once the principle of the development has been given planning permission.

Some basements can be built without the need to apply for planning permission.



Alan Baxter Associates were commissioned to provide up to date evidence on a range of basement matters. The draft policy in this document is based on their report.

A questionnaire was circulated to gather residents’ views of basements. The results of this questionnaire are on the Council’s website. The main findings are appended to this report.

Council officers have also worked with a small group of residents in Chelsea through the Neighbourhood Planning Vanguard project, in developing new policy and procedures.




The new policy does not propose to 'ban basements'.

It proposes to maintain the current position in relation to:

  • listed buildings, where basements are permitted under the gardens of listed buildings (subject to various matters) but not under the building itself;
  • sustainable urban drainage measures being required;
  • light wells etc needing to be discreetly located; and
  • measures to limit carbon emissions being required.

It proposes to limit basements to:

  • a single storey, defined as being of insufficient depth to allow horizontal subdivision in the future. This is on the basis that the larger the basement the greater the construction impact;
  • under gardens to maintain natural drainage, for basements never to exceed 75%of a garden, and could be significantly less than that, depending on the surface water conditions on the site. Also associated structures (such as escape stairs, roof lights) are to be discreetly located, in order to protect the character of the garden. This may indirectly affect basement size.

It proposes to give more weight to construction impact issues (by putting material currently in the SPD into the Core Strategy), including:

  • construction traffic;
  • construction methods;
  • hours that building work can be carried out; and
  • how to safeguard the structural stability of neighbouring buildings, although the exact structure would not be required through planning, but dealt with through Building Regulations and the Party Wall Act, as now.



It is proposed that applicants will be required to provide information at the time that the application is submitted (rather than related to a condition at the end of the process). On top of the existing requirements relating to Flood Risk and Carbon assessments, this will include assessments of:

  • construction traffic
  • how issues of noise, dust and vibration will be controlled during construction
  • how the applicant intends to safeguard the structure of remaining properties on site and adjoining properties, which will have to have been independently assessed by a second firm of engineers, although, as stated above, the exact structure would not be required through planning, but dealt with through Building Regulations and the Party Wall Act, as now


Permitted development

The Council is considering removing permitted development rights from those basements that can currently be built without the need to apply for planning permission. This will be done through an ‘Article 4 Direction’.

This is not to stop these basements taking place. They would be very likely to meet the criteria of the proposed policy set out above. Instead the purpose is to allow matters of construction impact – set out under procedure above – to be controlled. It could be done across the Borough, or it could be more specifically targeted in, for example, areas where streets are narrow or where construction is otherwise constrained. However, this has budgetary implications. When a planning application is required because permitted development rights have been removed, no fee is payable. This means the full cost of assessing applications must be carried by the Council. It is estimated that this cost, if Borough wide, is likely to be in the region of £65,000, though this could rise significantly were the number of eligible applications to increase.

1. The Core Strategy is the Council’s main planning document. It contains the policies against which planning applications are determined. It forms part of the Development Plan, and has to be approved by a government inspector before being adopted by the Council. [back]
2. A Supplementary Planning Document provides more information and detail on policies in the Core Strategy, and is approved by the Council’s Cabinet Member for Planning Policy. [back]