Hawk Teflon
Veteran
It holds up to 100,000 pounds of pressure on top (or something crazy like that). Also, there will be a vehicle parked over it for more "padding." It takes an unbelievable amount of force to crush it in. On top of that, once you have on installed, you have it registered with the fire department. Then, right after the storm, the FD comes out to those houses and starts checking the storm shelters.