Our Simple Planks are made from non-treated pine. We use untreated wood to help prevent sagging and splitting. Each end of the plank is notched and reinforced to furthed prevent against splitting and for better integrity. This also give a wider base when sitting in a jump cup. Because our Planks are made of non treated lumber, we do recommend treating your Plank with at least an exterior grade primer, or better an exterior grade paint or primer. This will help prevent against weathering and will prolong the life of your Plank, as well as improving it's appearance.