Decay and rot resistent redwood is the consumers #1 choice for their kids playsets. We use California Redwood for construction of our playsets where strength is a nessecity. Stronger than Western red cedar, which we use on other parts of the set, Redwood is used for Beams, Posts, Monkey bars and under towers. Redwood has qualities not found in other woods--even woods treated with chemicals. Redwood performance characteristics include resistance to shrinking, warping and checking in addition to durability. This means redwood projects age beautifully. In exterior use, redwood stays flat and straight with minimal warping, cupping or checking. Playsets made with redwood simply look better ten, fifteen and twenty years after construction. Redwood heartwood has grown-in resistance to decay and insects that is present throughout the lumber, not just on the surface. The wood exposed through sawing, boring or nailing is as decay-resistant as the surface.,* - ASTM F1148-05 - Standard Consumer Safety Performance Specification For Home Playground Equipment. All of our premium playsets meet or exceed the standard established by ASTM International. ASTM International sets voluntary safety standards for home playground equipment. While these standards are voluntary, you can be sure that play structures that are compliant are the safest on the market.