9.27.3.1 — Elements of the Second Plane of Protection

(1) Sheathing membranes shall conform to the performance requirements of CAN/CGSB-51.32-M, “Sheathing, Membrane, Breather Type”.

(1) Except as provided in Articles 9.27.3.4. to 9.27.3.6., at least one layer of sheathing membrane shall be applied beneath siding, stucco or masonry veneer. (2) Sheathing membrane required in Sentence (1) shall be applied so that joints are lapped not less than 100 mm. (3) Where sheathing membrane required in Sentence (1) is applied horizontally, the upper sheets shall overlap the lower sheets.

(1) Where non-wood-based rigid exterior insulating sheathing, or exterior insulating sheathing with an integral sheathing membrane is installed, a separate sheathing membrane is not required. (2) Where insulating sheathing is installed as provided in Sentence (1), (a) sheathing panels subject to moisture deterioration shall be sealed at all joints, and (b) the joints of sheathing panels not subject to moisture deterioration shall be, (i) sealed at all joints, or (ii) lapped or tongue and groove, and detailed to ensure drainage of water to the exterior.

(1) Except as provided in Article 9.27.3.6., where no sheathing is used, at least two layers of sheathing membrane shall be applied beneath the cladding. (2) All joints in the sheathing membrane required in Sentence (1) shall occur over framing, and the membrane shall be fastened to the framing with roofing nails or staples spaced not more than 150 mm along the edges of the outer layer of sheathing paper. (3) Wall sheathing is permitted to be used in lieu of one layer of sheathing membrane required in Sentence (1), and the thickness need not conform to Table 9.23.16.2.A.

(1) Sheathing membrane is permitted to be omitted beneath cladding when the joints in the cladding are formed to effectively prevent the passage of wind and rain in conformance with Sentence (2) or (3), as applicable. (2) Cladding consisting of sheets of plywood, hardboard, OSB, waferboard or fibre cement is considered to meet the requirements of Sentence (1), provided the cladding is applied so that, (a) all edges are directly supported by framing, (b) the vertical joints between adjacent sheets are sealed and, (i) covered with battens, (ii) shiplapped, or (iii) otherwise matched to provide weathertight joints, and (c) the horizontal joints between adjacent sheets are sealed and, (i) shiplapped, or (ii) otherwise matched to provide weathertight joints. (3) Metal siding consisting of sheets of metal is considered to meet the requirements of Sentence (1) where the joints between sheets are of the locked-seam type.

(1) Flashing shall consist of not less than, (a) 1.73 mm thick sheet lead, (b) 0.33 mm thick galvanized steel, (c) 0.46 mm thick copper, (d) 0.46 mm thick zinc, (e) 0.48 mm thick aluminum, or (f) 1.02 mm thick vinyl.

(1) Except as provided in Sentence (2), flashing shall be installed at, (a) every horizontal junction between claddings elements, (b) every horizontal offset in the cladding, and (c) every horizontal line where the cladding substrates change and where, (i) the substrates differ sufficiently for stresses to be concentrated along that line, or (ii) the installation of the cladding on the lower substrate may compromise the drainage of moisture from behind the cladding above. (2) Flashing need not be installed as described in Sentence (1), (a) where the upper cladding elements overlap the lower cladding elements by not less than 25 mm, (b) where, (i) the cladding above and below the joint is installed outboard of a drained and vented air space, and (ii) the horizontal detail is constructed so as to minimize ingress of precipitation into the air space, or (c) at horizontal construction joints in stucco, where, (i) the joint is finished with an expansion-contraction strip, and (ii) the cladding is installed outboard of a drained and vented air space. (3) Flashing shall be installed over exterior wall openings where the vertical distance from the bottom of the eave to the top of the trim is more than one-quarter of the horizontal overhang of the eave. (4) Flashing described in Sentences (1) and (3) shall, (a) extend not less that 50 mm upward inboard of the sheathing membrane or sheathing installed in lieu of the sheathing membrane, (b) have a slope of not less than 6% toward the exterior after the expected shrinkage of the building frame, (c) terminate at each end with an end-dam, (i) with a height in millimetres not less than 25 mm or 1/10 of the value of the 1 in 5 driving rain wind pressure in Pa, and (ii) at the height defined in Subclause (i), extending to the face of the adjacent cladding, (d) lap not less than 10 mm vertically over the building element below, and (e) terminate in a drip extending not less than 5 mm outward from the outer face of the building element below. (5) Where the sills of windows and doors installed in exterior walls are not self-flashing, flashing shall be installed between the underside of the window or door and the wall construction below.