It’s moisture-resistant, not waterproof. Standard OSB can handle brief rain during construction, but it still needs protection once the building is closed in.
Choose the right grade for conditions (e.g., OSB/3 or OSB/4 for humid areas), keep a 3 mm (1/8″) gap between panels for swelling, and finish the system with a weather-resistive barrier, flashing, and fast roof/wall dry-in.
Seal cut edges when you can, store panels flat and off the ground, and avoid standing water—that’s what causes edge swell and cupping.
