(1) Where hydrostatic pressure occurs, waterproofing is required for assemblies separating interior space from the ground to prevent the ingress of water into building assemblies and interior spaces.
(2) Waterproofing is required for roofs of underground structures to prevent the ingress of water into building assemblies and interior spaces.
Article 220.127.116.11. Ontario Regulation 332/12 Building Code, Information published by oncodes.ca for educational purposes only.
Waterproofing is needed where there is a likelihood of hydrostatic water pressure and requires the services of a qualified professional to identify which measures are to be taken to deal with the water and the forces imposed on the foundation. Waterproofed foundations need not be dampproofed. For walls, waterproofing consists of an impermeable membrane, such as two layers of bitumen-saturated felt. The layers of felt are attached to the wall and each other and covered with liquid bitumen. Waterproofing materials for ICF foundations must be compatible with the foam formwork/insulation.
Floor slabs must also be waterproofed where hydrostatic pressure could be an issue. The waterproofing materials must consist of a membrane sandwiched between two layers of concrete, each layer not less than 75 mm (3 in.) thick. The floor membrane must be sealed to the wall membrane. In many cases, foundations subjected to hydrostatic pressure are also equipped with a means of relieving the water pressure to prevent structural damage.
Source : Canada Mortgage and Housing Corporation (CMHC)