Plywood and OSB (Oriented Strand Board) are the two most common materials used for roof decking, each with its own strengths and drawbacks. Plywood is made from thin layers of wood veneer glued together, giving it a strong, stable, and moisture-resistant structure. It tends to perform better under heavy loads and is less likely to swell or warp when exposed to moisture. OSB, on the other hand, is made from wood strands compressed with adhesives. It's generally more affordable and provides a uniform thickness, but it can be more sensitive to prolonged exposure to moisture, which sometimes leads to swelling or edge deformation. Both materials meet building codes and modern standards, so the choice often depends on budget, climate, and specific roofing needs. When diagnosing roof decking issues, visible water damage, sagging, or soft spots are red flags indicating the decking may have weakened, whether plywood or OSB.
Homeowners can safely check for roof decking problems from the attic by inspecting for signs of water intrusion, mold, or bulging areas under the roof. Tapping areas with a gentle tool can reveal weak or deteriorating wood when the sound is hollow or soft. However, because safety and accuracy are critical, it's best to call a roofer if you notice any sagging or water stains on interior ceilings, or if a professional opinion is needed on decking suitability, especially before roof replacement. When asking a contractor, inquire whether they recommend plywood or OSB for your specific roofing system and why, and whether their choice will affect your roofing warranty coverage. Understanding these points can help ensure you get a roof decking material that balances durability, cost, and long-term performance for your home.