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Basements and Shafts

Designers Knowledge Base

This includes basements for offices, residential blocks, warehouses, car parks etc. Shafts are those of large diameter i.e. over 3 metres.


In specifying such basements or shafts the designer should be aware of, and assess the risks from, the following principal hazards.

Some possible hazards and risks

  • falls from height: into the excavation or shaft
  • falling materials into, or from the sides of, the excavation or shaft caused by inadequate support
  • health hazards caused by contaminated ground or water (Weil's disease?)
  • flooding by sudden inrush of ground water or effluent
  • electrocution or explosion caused by contact with electrical services
  • health hazards caused by gas build up such as methane exhaust fumes etc.


Site survey and ground investigation to locate adjacent structures and to ascertain the soil condition, water table level etc. Locate possible water courses or aquifers.

Possible design options

  • following site investigation determine best excavation methods and identify ground water problems or hazardous materials to be dealt with
  • consider effects of excavations on overhead and underground services and consider possibility of diverting them
  • consider excavation with contiguous bored piles which will form permanent walls
  • consider effects of excavation on structural integrity of adjacent structures
  • specify support details that contain or exclude contaminants
  • consider possible necessity to shore adjacent structures
  • design assumptions on construction sequence and methods to be identified in health and safety plan