Hello all! I am from northern Iowa where the winters are long and cold. I am building an in ground pool from a do it yourself online company. I haven't decided on a company yet but they all have about the same choices, steel walls or polymer with a vinyl liner. I like the though of steel walls because they are sturdier when assembling them and I would think they would withstand the pressure of the water freezing over winter, which brings me to my next question. How does the concrete pad around the pool not crack when the ice in the pool expands, I once heard that people would half submerge inner tubes in the middle of the pool to allow for expansion, but the pool dealers say it isn't a problem. I building flat bottom play pool 42 inches deep, the same size as the wall. I should mention that I am an experienced home builder and have years of excavation and basement experience so they project seems very doable for me.