Hertsmere Council’s draft revised Planning and Design Guide Part D: Guidelines for High Quality Sustainable Development, contains measures clarifying what is acceptable around the design, size, proportion, access and other characteristics of basements in new or existing homes, as well as their impact on rear gardens, trees and car parks.
Among its policies, the document says that, where a basement extension is proposed to an existing house, "the basement should be entirely beneath the ground and the existing ground levels around the house should not be artificially lowered in order to create the appearance of an additional storey".
A statement from the council said that underground building projects in Hertsmere tend to be smaller-scale than those which have made headlines in London in recent years, but the council has seen an increase in planning applications involving basements.
Harvey Cohen, the council's portfolio holder for planning and localism, said: "We want all schemes involving basements to be sustainable and proportionate to the home and the location, and constructed in a way that minimises the disruption and impact on the environment."
The document also sets out council’s approach to taller buildings, as well as guidance on the demolition and replacement of buildings in conservation areas; changes to guidelines on overlooking distances between buildings; clarification on appropriate roof types; and new restrictions for gates in front of properties.
Cohen said: "A lot of these proposed changes have been made to take account of the introduction of new national and local policies, but we’re also making them in response to changes in the kinds of developments we are seeing in Hertsmere".
The consultation runs until Monday 21 November and can be found here.