Policy information sourced from the Islington Local Plan

DH4 Basement development

  • All basement development must be proportionate to its site and context.
  • The Council will only permit basement development where it is demonstrated to its satisfaction that the proposal would not cause an unacceptable degree of harm to:
    1. the structural stability of the existing building, nearby buildings, trees and any infrastructure;
    2. the structural, ground, or water conditions of the area;
    3. the architectural character of the building;
    4. the character and amenity of the area; or
    5. the significance of heritage assets including conservation areas and listed buildings.
  • Applicants proposing basement development must provide evidence of the impact of basement development in the form of a Structural Method Statement (SMS), which satisfies the criteria in Part B.
  • For residential basement development (including extensions):
    1. a basement must cumulatively occupy less than 50% of the original garden and/or unbuilt area; or the area of a basement which is outside the footprint of the host building must total no more than 50% of the area of the footprint of the host building, whichever is the lesser;
    2. a basement must not involve excavation of more than one (1) storey below the lowest original habitable floor level;
    3. the height of a basement must not exceed 3m floor to ceiling height;
    4. where considered appropriate in the local context, lightwells and other external manifestations must be modest in size, discreetly located, and designed to protect and enhance the character and appearance of the area;
    5. basements must be designed to preserve existing gardens, and must reinforce the visual relief that soft landscaping between buildings provides; and
    6. basement development must not significantly alter the prevailing garden level.

For more information please see the Islington Local Plan