You are installing a subfloor using 19 mm T&G OSB panels on floor joists spaced at 400 mm o.c. After laying the first row, you notice that the end joints of the panels in the second row are aligning directly above the end joints of the panels in the first row. What is the corrective action required?

Question: You are installing a subfloor using 19 mm T&G OSB panels on floor joists spaced at 400 mm o.c. After laying the first row, you notice that the end joints of the panels in the second row are aligning directly above the end joints of the panels in the first row. What is the corrective action required?

Answer options:

• Proceed with installation, as the tongue-and-groove joint will adequately transfer loads.
• Apply extra construction adhesive to the aligned end joints for reinforcement. ✅ Shift the panels in the second row to stagger the end joints by at least one joist space (minimum 400 mm).
• Add blocking beneath every aligned end joint to provide additional support.

Correct answer: Shift the panels in the second row to stagger the end joints by at least one joist space (minimum 400 mm).

Explanation: Subfloor panels must be staggered so that end joints in adjacent rows do not align. This helps transfer loads across the floor and prevents potential weak points, minimizing deflection and squeaks. A minimum stagger of one joist space is typically required to ensure structural continuity.