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foundation wall (Figure 56) for the support and fastening of the joists and a rim joist attached to the ends of the joists. The sill plate is usually supported on the top of the foundation wall, in which case the bottom of the sill plate should be at least 150 mm (6 in.) above the finished grade, or else it must be separated from the concrete by 0.05 mm (2 mil) polyethylene or Type S roll roofing, or the wood framing must
be preservative-treated. A foam gasket should be placed between the concrete and the sill plate to reduce or eliminate air leakage at this juncture. Where it is desirable to lower the elevation of the main floor in relation to the top of the foundation, the top of concrete foundation walls may be reduced to 90 mm (31⁄2 in.) in thickness (Figure 57). If siding or stucco is used as an
56 Sill-plate method used in platform construction bottom wall plate subfloor wood I-joist or wood floor joist rim board anchored sill plate foam gasket or extension of air barrier mortar levelling bed 200 mm (8 in.) minimum for stucco and wood siding 150 mm (6 in.) minimum for masonry and metal and vinyl siding finished grade
57 Floor joists supported on a ledge formed in the foundation wall wall finish air/vapour barrier insulation wall stud wall sheathing
finish flooring subfloor
sheathing membrane rigid insulation over 2 × 4 framing wall plate 200 mm (8 in.) minimum bottom sill plate anchored to foundation floor joist toenailed to sill plate continuous header 12 mm (1⁄2 in.) air space if rim joist is untreated
sill plate anchored to foundation with anchor bolts