9.3.2.9.Termite and Decay Protection

(1) In localities where termites are known to occur, (a) clearance between structural wood elements and the finished ground level directly below them shall be not less than 450 mm and, except as provided in Sentence (2), all sides of the supporting elements shall be visible to permit inspection, or (b) structural wood elements, supported by elements in contact with the ground or exposed over bare soil, shall be pressure-treated with a chemical that is toxic to termites. (See Note A-9.3.2.9.(1)) (2) In localities where termites are known to occur and foundations are insulated or otherwise finished in a manner that could conceal a termite infestation, (a) a metal or plastic barrier shall be installed through the insulation and any other separation or finish materials above finished ground level to control the passage of termites behind or through the insulation, separation or finish materials, and (b) all sides of the finished supporting assembly shall be visible to permit inspection. (3) Structural wood elements shall be pressure-treated with a preservative to resist decay where the vertical clearance between structural wood elements and the finished ground level is less than 150 mm. (See Note A-9.3.2.9.(3)) (3.1) In localities where termites are known to occur and where windows or other openings at or below grade contain wood elements, the bottom of window wells or adjacent ground shall be at least 150 mm below the nearest wood unless the wood is pressure-treated with a chemical toxic to termites. (4) Structural wood elements used in retaining walls and cribbing shall be pressure-treated with a preservative to resist decay, where (a) the retaining wall or cribbing supports ground that is critical to the stability of building foundations, or (b) the retaining wall or cribbing is greater than 1.2 m in height. (See Note A-9.3.2.9.(4)) (5) Where wood is required by this Article to be treated to resist termites or decay, such treatment shall be in accordance with Table 2, “Use Categories for Specific Products, Uses, and Exposures,” of CAN/CSA-O80.1, “Specification of treated wood,” as follows: (a) Use Category 1 (UC1), where the wood member is used in (i) interior construction, (ii) above-ground applications, and (iii) applications where the wood member remains dry, (b) Use Category 2 (UC2), where the wood member is used in (i) interior construction, (ii) above-ground applications, and (iii) applications where the wood member may be subjected to occasional sources of moisture, (c) Use Category 3.2 (UC3.2), where the wood member is used in (i) exterior construction, (ii) above-ground applications, and (iii) applications where the wood member is uncoated or is used in a configuration conducive to moisture accumulation, (d) Use Category 4.1 (UC4.1), where (i) the wood member is used in contact with the ground, (ii) the wood member is used in contact with fresh water, or (iii) the vertical clearance between the wood element and the finished ground level is less than 150 mm and the wood elements are not separated from permeable supporting materials by a moisture barrier, or (e) Use Category 4.2 (UC4.2), where the wood member is used in critical structural components, including permanent wood foundations. (6) Where wood is protected in accordance with UC1 or UC2 using an inorganic boron preservative, the wood shall be (a) protected from direct exposure to water during and after the completion of construction, and (b) separated from permeable supporting materials by a moisture barrier that is resistant to all expected mechanisms of deterioration in the service environment if the vertical clearance to the ground is less than 150 mm. (7) Wood that is required by this Article to be treated to resist termites or decay shall be identified by a mark to indicate the type of preservative used and conformance to the relevant required Use Category.