The Ontario Building Code | Protection from Dampness
220.127.116.11. Protection from Dampness
(1) Except as permitted in Sentence (2), wood framing members that are not pressure-treated with a wood preservative and that are supported on concrete in contact with the ground or fill shall be separated from the concrete by not less than 0.05 mm polyethylene film or Type S roll roofing.
(2) Dampproofing material referred to in Sentence (1) is not required where the wood member is at least 150 mm above the ground.