I am having to replace my top subfloor because it was too much work to prep it for tile as the three layers of linoleum that the previous owners had left was just too much to handle. Anyway when I got to the first layer of subfloor it is 1/2". What would you recommend putting on top of that to make it nice an sturdy for tile? What would the professionals do to get it ready. I am going to be using 12x24" tiles with electric radiant heat below. Thanks.