Which material is not approved by any manufacturer for deck waterproofing purposes?

The choice identifying OSB (Oriented Strand Board) as the material not approved by manufacturers for deck waterproofing purposes is accurate due to the inherent properties of the material. OSB is made from wood strands that are oriented and bonded with adhesives. While it is a cost-effective and commonly used building material, it has limitations when it comes to durability in wet conditions.

Manufacturers often recommend plywood, concrete, and metal for deck waterproofing because these materials possess better resistance to moisture and structural integrity in outdoor applications. Plywood, for example, is treated to withstand moisture and is often used in various building and roofing applications. Concrete is inherently water-resistant, making it suitable for deck surfaces. Metal components are typically used for their durability and waterproofing qualities, especially in roofing and decking systems.

In contrast, the susceptibility of OSB to moisture damage, swelling, and delamination makes it unsuitable for use in waterproofing applications. This is why it is not recommended by manufacturers for deck waterproofing.