mortar or portland cement to fix flagstone to concrete slab
by John Colasanti
(Livonia, Michigan, USA)
My local stone dealer says cement isn't a bonding agent like mortar is and should not be used to place flagstone on a concrete bed. Your instructions call for portland cement and say to "Don't use masonary. what is your rational for one over the other.
also I've been told that some contractors place thin set indoor outdoor tile mortar on the slab and on the back of the flagstone with the portland in between. They use a product called Tec full flex latex modified mortar. have you ever heard of this practice. I'm in Michigan where temperature extremes and freeze thaw cycles are brutal to masonary.