Recycled Wood/Plastic Composite Lumber
According to the National Association of Home Builders, this 50-50 combination of wood fibers and waste plastics is more durable and less toxic than conventional treated lumber. The material is also more rigid than pure plastic lumber because the wood fibers add extra strength.
While it's more resistant to mold and rot, the composite lumber is more rigid in the cold and more pliable in the heat than plastic lumber. It's also significantly more expensive than conventional treated lumber products.