[JavaBrewer]

KT, have you ever used a crack isolation product called Red Guard? Any insider info on it's performance vs. a traditional crack isolation layer sold in many tile stores?

Also, if PBH is referring to a crack isolation product then I don't think Randy needs to worry about that as he's installing over wood subfloors with concrete backer board (CBU) and thinset. Folks typically use things like Red Guard for tile install over existing concrete slab. It prevents future hairline cracks in the slab from transmitting up to the tile.