The Ontario Building Code | Backfilling
(1) Where an excavation is backfilled, the backfill shall be placed so as to,
(b) prevent detrimental movements.
(2) The material used as backfill or fill supporting a footing, foundation or a floor on gradeshall be of a type that is not subject to detrimental volume change with changes in moisture content and temperature.
4.2.6. Shallow foundations