Bale Board plastic lumber
BaleBoard recycled plastic lumber is a great choice as a moisture barrier under wood / metal stud walls, or for other utility applications. Customers have used it for planter boxes, garden edging, and bench seats, etc. Available in slate grey, in close to standard lumber dimensions stocked as 2" x 4" x 12', 2" x 6" x 12' and 4" x 4" x 10 foot. Due to the nature of manufacture with recycled material, the possibility of small air voids exists in the centre of the product. Since no moisture is absorbed - it won't rot in damp environments.
As with all plastics, expansion and contraction occur with exposure to heat or cold.