Policy information sourced from the Richmond Upon Thames Local Plan

Policy 54 Basements and Subterranean Developments

A. The Council will resist subterranean and basement development of more than one storey below the existing ground level to residential properties or those which were previously in residential use.

B. Proposals for subterranean and basement developments will be required to comply with the following:

  1. extend to no more than a maximum of 50% of the existing garden land or more than half of any other undeveloped garden area (this excludes the footprint of the original building);
  2. demonstrate the scheme safeguards the structural stability of the existing building, neighbouring buildings and other infrastructure, including related to the highway and transport; a Structural Impact Assessment will be required where a subterranean development or basement is added to, or adjacent to, a listed building.
  3. use natural ventilation and lighting where habitable accommodation is provided to ensure the health and well-being of its occupants;
  4. include a minimum of 1 metre naturally draining permeable soil above any part of the basement beneath the garden area, together with a minimum 200mm drainage layer, and provide a satisfactory landscaping scheme;
  5. demonstrate that the scheme will not increase or otherwise exacerbate flood risk on the site or beyond, in line with Policy 8 ‘Flood Risk and Sustainable Drainage (Strategic Policy) ‘; a site specific Screening Assessment, undertaken by a chartered professional, is required to assess likely impacts from subterranean development within throughflow and groundwater policy zones and/or in an area with >=25% susceptibility to groundwater flooding; if the Screening Assessment determines that the proposed subsurface development may have an impact on the local environment, or if it determines that further investigation work is required, then a Basement Impact Assessment is required;
  6. where the proposal contains a waste outlet, install a suitable (positively) pumped device to protect the development from sewer flooding, in line withPolicy 8 ‘Flood Risk and Sustainable Drainage (Strategic Policy) ‘;
  7. demonstrate as part of a Construction Management Plan that the development will be designed and constructed so as to minimise the impact during construction and occupation stages (in line with Policy 53 ‘Local Environmental Impacts’);
  8. demonstrate that the proposal does not cause loss, damage or adverse impact to biodiversity, including trees, and amenity value; and
  9. externally visible elements such as light wells, roof lights and fire escapes need to be sensitively designed and sited to avoid any harmful visual impact on neighbouring properties or visual amenity.

C. Proposals for subterranean and basement developments, including extensions, as well as lightwells and railings, will be considered against the advice set out in the Council’s SPDs relating to character and design as well as the relevant Village Planning Guidance and the forthcoming SPD on Basements and Subterranean Developments. Applicants will be expected to follow the Council’s Good Practice Guide on Basement Developments. Any sub-surface, basement and cellar proposals within throughflow and groundwater policy zones and/or in an area with >=25% susceptibility to groundwater flooding need to follow the guidance set out in the Council’s Basement Assessment User Guide.

For more information please see the Richmond Upon Thames Local Plan