In this study, a tornado safe room door built from wood products and steel sheeting was developed and impact-tested according to tornado safe room standards. Results indicate that an door constructed from as few as two sheets of 23/32-in. (18.26-mm) construction-grade plywood and overlaid with 18-gauge (0.05-in.- (1.27- mm-) thick) steel can pass the required impact test.
Falk, Robert H.; Bridwell, James J. 2016. Development of a tornado safe room door from wood products: door design and impact testing. Research Paper FPL-RP-686. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 17 p.