Strip and trench fill foundations

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Strip and trench fill foundations shall comply with the Technical Requirements and provide adequate support to all load-bearing elements.

Strip and trench fill foundations that comply with the guidance in this chapter will generally be acceptable.

Foundations should be designed by an engineer in accordance with Technical Requirement R5 where:

  • buildings exceed three storeys in height
  • supporting/retaining walls form habitable rooms below ground
  • trench fill foundations are deeper than 2.5m
  • they will be deeper than those of an adjoining construction.

Elements of the building requiring foundations include:

  • external walls
  • separating (party) walls
  • internal load-bearing walls
  • chimney breasts
  • piers.

In Scotland, a sleeper wall is defined as a load-bearing element and therefore should be provided with a suitable foundation.

In England, Wales, Northern Ireland and the Isle of Man, sleeper walls should be provided with suitable foundations where the oversite concrete is:

  • cast on shrinkable clay soils where heave could take place
  • cast on infill deeper than 600mm
  • less than 100mm thick.