A carpenter is specifying subfloor sheathing for a floor system over engineered wood joists (I-joists) that are spaced at 600 mm on centre. The floor is intended for heavy pedestrian traffic and potential point loads. Which subfloor panel thickness would meet or exceed minimum typical building code requirements for this joist spacing?

Question: A carpenter is specifying subfloor sheathing for a floor system over engineered wood joists (I-joists) that are spaced at 600 mm on centre. The floor is intended for heavy pedestrian traffic and potential point loads. Which subfloor panel thickness would meet or exceed minimum typical building code requirements for this joist spacing?

Answer options:

• 12.7 mm Plywood (1/2")
• 15.9 mm OSB (5/8")
• 18.3 mm Plywood (23/32") ✅ 22.2 mm OSB (7/8")

Correct answer: 22.2 mm OSB (7/8")

Explanation: For joist spacing of 600 mm on centre, building codes in Canada typically require a subfloor thickness of at least 22.2 mm (7/8 inch) for OSB or 18.3 mm (23/32 inch) for plywood, assuming panel identification for joist spacing. Given the options, 22.2 mm OSB would be the most suitable and code-compliant choice for the specified joist spacing and anticipated loads.