Council to review its current planning policy framework

As basement extensions become an increasingly popular way of extending Chiswick homes, the Area Monitoring Committee has been considering a report compiled on the current planning policy framework.

The main points of the report are:

• that most of Chiswick is within the acknowledged flood zone
• there are potential issues with basements undermining adjoining properties if they are not designed and constructed properly
• there is a need for a robust and thorough Policy in respect to residential basement extensions

The report, which was considered at the last Chiswick Area Monitoring Committee meeting, was prepared in response to requests from the Committee for more information on policy guidance for residential basement developments.

There are approximately 16,000 homes and businesses within the London Borough of Hounslow are potentially at risk of flooding, the vast majority of these falling within the three Chiswick wards. The Council’s current planning guidance in respect of basements is limited to ensuring risks to life and property from flooding is minimised. There are no specific guidelines for the design of basements or recommendations to mitigate their impacts when under construction.

Currently building a basement is development under the planning system. Some forms of minor development, including the enlargement of a dwelling / house, may be ‘permitted development’ where planning permission is not required, subject to certain criteria not being breached.
Therefore a basement extension may be constructed as ‘permitted development’ to a single dwellinghouse as long as it falls outside the exclusions listed in Class A of the Town and Country Planning (General Permitted Development) Order. This means in some cases a basement extension would not need planning permission, and so no design guidance would apply and no conditions could be applied to the development.

The main instances where permitted development rights for basements would not apply are:

• Listed buildings (Listed Building consent needed)
• Flats
• Houses that have no permitted development rights
• Basements that extend forward of the front wall of the house
• Basements that extend beyond the specified limits for extensions (to the front, rear and side walls of the original house)

The report noted that within the Borough of Hounslow, basement extensions are most likely to be made in Chiswick and there is anecdotal evidence of increased demand for such extensions given high property prices, restrictive policies regarding extensions and people’s desire to remain in the area allied with the wish to extend their houses. As the majority of the three Chiswick wards are within a flood zone, the policies regarding flood risk referred to above are applicable when assessing planning applications for basement extensions.

Basement extensions to listed buildings are generally opposed, as they are likely to unduly alter the special architectural and historic character of the building. In conservation areas, development must preserve or enhance the appearance and character of the conservation area.

The Committee agreed that further discussion on the subject was needed before a new planning policy framework could be put in place.

August 3, 2010