(1) Except as provided in Sentence (4) and Article 188.8.131.52., where the exterior finished ground level is at a higher elevation than the ground level inside the foundation walls, exterior surfaces of foundation walls below ground level shall be dampproofed.
(2) Except as provided in Sentence (3) and Article 184.108.40.206., floors-on-ground shall be dampproofed.
(3) Floors in garages, floors in unenclosed portions of buildings and floors installed over granular fill in conformance with Article 220.127.116.11. need not be dampproofed.
(4) Dampproofing in Sentence (1) is not required where the exterior surfaces of foundation walls below ground level are waterproofed.
Article 18.104.22.168 Ontario Regulation 332/12 Building Code, Information published by oncodes.ca for educational purposes only.
Dampproofing is necessary for all foundations that contain habitable space to restrict the movement of soil moisture into the wall. Dampproofing materials include bitumen, polyethylene or other sheet material. In poorly-drained soils or soils with a high water table, waterproofing will be required.
Dampproof concrete and unit masonry walls below grade with a heavy coat of bituminous material applied on the exterior surface from the footings to the finished grade line. Such a coating is usually sufficient to make the wall resistant to surface water moving down to the footing drainage system. Mineral fibre insulation or drainage layers are recommended to drain water away from the foundation walls.
Source : Canada Mortgage and Housing Corporation (CMHC)