5.1.4.2.

(1) Except as provided in Sentence (2), materials used in building components and assemblies that separate dissimilar environments, or in assemblies exposed to the exterior, shall be,

(a) compatible with adjoining materials, and

(b) resistant to any mechanisms of deterioration that may reasonably be expected, given the nature, function and exposure of the materials.

(2) Material compatibility and deterioration resistance are not required where it can be shown that incompatibility or uncontrolled deterioration will not adversely affect any of,

(a) the health or safety of building users,

(b) the intended use of the building, or

(c) the operation of building services.

(3) Design and construction of assemblies separating dissimilar environments and assemblies exposed to the exterior shall be in accordance with good practice such as described in CSA S478, “Guideline on Durability in Buildings”.