Polyethylene structural foam is a non-toxic material which will not splinter and irritate your dog's skin. No nails, staples or screws are used. Unlike wood, structural foam will never rot. Material has molded-in color that will never chip or splinter. Soaps will not damage material. Structural foam's non-porous surface will prevent fleas and ticks from burrowing into material and incubating. Easily cleaned with water hose! Unlike wood, solid plastic or fiberglass, structural foam material has foam sandwiched between solid outer walls. Warmer in winter, cooler in summer! Thick raised floor insulates from the cold wet ground and grass.