Raft, pile, pier and beam foundations

Also see:
5.1
5.2
5.4

4.4.13Resistance to moisture

Raft, pile, pier and beam foundations shall prevent the passage of moisture to the inside of the home and, where necessary, include a drained cavity and damp proof membranes.

Cavity walls should drain below the DPC and should:

  • prevent water crossing from the outside to the inside
  • prevent the flooding of cavities above the DPC
  • drain below the DPC
  • have a minimum 225mm clear cavity below the DPC where strip, trenchfill or ground beams are used, or have a minimum 150mm clear cavity below the DPC where other types of foundations are used, provided that weep holes and other necessary measures are taken to ensure that the cavity can drain freely.

DPC cavity trays are not an acceptable waterproofing to the edges of specialised foundations, such as rafts and ground beams.