The need to provide daylighting and comply with building regulation requirements for ventilation of habitable rooms will generally be met by incorporating openable windows in the same manner as above ground. This may entail adjusting the external ground levels in partially belowground basements, and would mean forming open areas for windows in fully below-ground basements.

A primary factor in improving the quality of a room in a basement is the provision of natural light. Inclusion of glazed windows or doors provides greater possibility of future adaptation and uses, as well as sustainability benefits by reducing dependence upon artificial lighting.

There are many techniques for improving the level of natural daylight and ventilation in basement spaces; determined by various factors including the proposed use of the space, proximity to boundary and plot size.

Solutions for habitable spaces include simple direct lighting through windows, glazed doors or roof lights. Other supplementary solutions include the use of sun pipes or use of borrowed light with mirrors, glazed floors or stairwells.

Daylighting techniques

  • Partially sunken light wells and windows.
  • Full depth external spaces with glazed doors providing separate private amenity space and potential access to the garden or alternative entrance from the street.
  • Sunpipes and pavement lights are suitable for basement spaces extending beyond the footprint of the building above. They provide permanent natural lighting with additional security but limited views.
  • Glazed roof lights can wash spaces with natural light and provide sky views and natural ventilation if openable.
  • Mirrors facing and adjacent to, window openings can significantly increase the perceived light levels and provide depth of field. Light and/or polished surfaces will generally improve the sense of space and daylight levels in a room.
  • Glazed floors, particularly below upper floor roof lights or windows, can be useful additional sources of light but will require fire-rated glazing to maintain fire compartmentation between floors.
  • Light from upstairs rooms can brighten lower ground floor spaces via the stairwell. This arrangement will depend upon the specific fire arrangements of individual properties and may require an upgraded fire resistance or detection system.

Mirrors facing, and adjacent to, window openings can significantly increase the perceived light levels in a basement.

Please refer to Part F ( Ventilation) of our building regulations guide for further information. All information correct as of 2013 amendments.