Substructure and ground-bearing floors

5.1.7Fill below floors

Fill, including made ground, trench backfill and infill below ground-bearing floor slabs shall provide full and consistent support to ground-bearing slabs.

Where more than 600mm of infill is required at any point within a self-contained area, or the bearing capacity and nature of the ground varies, the floor over the self-contained area should be of suspended construction.

Infill under slabs and backfill in trenches should be properly placed and mechanically compacted to form a stable mass in layers not exceeding 225mm. Concrete may be used as an alternative to backfill in trenches.