Ground-bearing floors over deep fill or sulphate-rich ground
600 mm
When a concrete floor is constructed over deep fill exceeding 600mm, it should be designed as a suspended floor rather than ground-bearing
When a concrete floor is constructed over deep fill exceeding 600mm, it should be designed as a suspended floor rather than ground-bearing. If the ground or groundwater contains sulphates, an impervious membrane is required between the concrete slab and the ground to protect the concrete from chemical attack.
Basis in regulation
BS 8103-1
Read the source
How to check it on site
Verify the depth of fill beneath floor slabs and ensure appropriate sulphate-resistant measures or suspended floor construction are in place.
Common failure
Concrete floors are laid directly on deep, uncompacted fill, leading to settlement and cracking, or lack of sulphate protection results in concrete degradation.
Last updated 23 August 2026. This is our editorial summary of publicly available regulation, not building control approval or a warranty determination.