Which decking material is known for holding the most moisture?

OSB, or oriented strand board, is known for holding more moisture compared to other decking materials. This is primarily due to its composition and manufacturing process, which involves strands of wood that are bonded together with adhesive under heat and pressure. OSB's structure can allow water to be absorbed more readily, and when it becomes saturated, it can swell and lose its structural integrity.

In contrast, materials like plywood consist of thin layers of wood veneer glued together in a cross-laminated pattern, which can provide better moisture resistance due to the overlapping grain direction. Metal decking and concrete decking are inherently more resistant to moisture since they do not absorb water in the same way as wood products. Metal can corrode if not properly treated, and concrete can wick moisture but does not retain it like wood-based products. Understanding the moisture-holding characteristics of these materials is crucial for making informed decisions about roofing systems and their durability over time.