Policy information sourced from Highgate Neighbourhood Plan

DH7: Basements

Where basement development does not fall in the scope of permitted development, and where there is evidence that there may be problems with drainage or flooding, applications for basement development will be supported only where they meet the requirements set out within this policy.

Impact Assessment requirements:

Any assessment on the impact of a basement development should demonstrate that:

  1. There will be no adverse effect from subterranean development on the structural stability of adjacent properties and associated potential damage;
  2. There will be no possibility of irreparable damage to the local water regime both in terms of ground water diversion and surface water flooding;
  3. There will be no individual or cumulative impact of development on the character and biodiversity of gardens and adjacent open spaces, particularly in designated conservation areas and those areas adjacent to Highgate’s Major Open Spaces (identified in 3.4.2).

Where there is evidence that there have been problems with drainage or flooding, or desk top surveys indicate problems may arise, applicants will be required to demonstrate to the satisfaction of the LPA that development will not cause or exacerbate such problems.

Under no circumstances should construction be allowed to proceed where there is evidence that damage to neighbouring properties would exceed Burland Scale 1.

Protection for Neighbours:

Where a Construction Management Plan (CMP) is secured, it should be submitted, and must be approved by the LPA, prior to the commencement of works.

Limiting Environmental/Ecological Impacts:

Any basement development should normally be expected to allow for a minimum of one metre of permeable soil above any part of the basement beneath a garden to support biodiversity and larger trees/planting. This depth should be greater if necessary to preserve landscaping consistent with neighbouring properties.

All basement developments should incorporate a positive pumped device or other suitable flood prevention device to avoid the risk of sewage backflow causing sewer flooding.

For more information please see the Neighbourhood Plan