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METRIC AND IMPERIAL DIMENSIONS Canadian Wood-Frame House Construction provides both metric (SI) and imperial units. The National Building Code of Canada uses metric units and these govern whenever strict interpretations of Code requirements are required. Imperial units of measure (feet and inches) are still commonly used for wood-framing materials and house construction technology. Imperial sizes for lumber are nominal sizes (the rough sawn sizes before planing and dimensional changes resulting from drying). For example, a wood member with a nominal size of 2 × 4 in. has a finished size of about 11⁄2 × 31⁄2 in. The metric dimensions for lumber are actual sizes (for example, 38 × 89 mm). Every reasonable effort has been made to provide accurate conversions of metric dimensions to imperial equivalents; however, it remains the responsibility of designers and builders to comply with building code requirements. Some conversion factors are given in Table 1 (p. 263). Consult the local building department to determine the units measurement required for house plans.
Canada Mortgage and Housing Corporation
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