We are talking about tile that explode in the middle of the night shooting shrapnel everywhere. I lived in a place like that 17 years ago. It is always on a frigid (for here) night after 3 or 4 days of cold weather. That's how long it takes for a concrete structure to cool. It's pretty freaky and dangerous. The bigger the tile the more dramatic it is. The next time I get a call from some folks (I get 2 or 3 a year) who are scared shitless I will invite you over