Flooring Tile Help

The mere act of putting the thinset on particle board to attach the cement board COULD cause swelling/separation problems. Not my field of expertise, but I would say the particle board needs to be replaced with plywood unless there is some sort of "membrane" installed to prevent (guarantee) the particle board isn't exposed to moisture. As Bud stated, it doesn't take much to totally ruin your new floor. Water can seep in through the grout if it isn't sealed properly or a fair sized "spill"/accident near a wall where it can get under the baseboard and penetrate to the particle board. When in doubt, go to the mfgr.'s web site for the tile you are going to use. They will have an outline for the proper installation procedure and the proper substrate necessary to keep your warranty valid. I'm sure someone more knowlegeble (in the trade) will reply......