So the floor in your shed is just as old as the foundation. over time it has been subjected to hours of people walking on it, chemicals being spilled, and tools being dropped. your shed floor has been soaked by rain when someone left the door open, you name it and it has probably happened to the floor.. Pressure-treated plywood is an exterior-grade plywood that will resist rot and decay for a lifetime. it is the preferred flooring material for an outdoor shed.. We offer rubber shed flooring options that are inexpensive, easy to install and quick to implement. if you are turning your shed into a functional storage area, it is important to install shed flooring that is tough enough to withstand abrasive conditions and protect the floors underneath..