Weight on slab I have read many articles about a basement fallout shelter and noticed that no mention is made on the strenght of the basement slab. Especially the older cold war examples of building concrete walls on the slab. Just building a concrete wall on a slab seems to me silly without consulting a architect. The weight is significant of the wall alone but adding a 12″ concrete sealing is just a big load on just 4″ of slab. I like to hear if there is anyone thinking of the consequences and how to mitigate this concern.