[Daniel Holzman]

We have rough slate behind our house, installed over a sand base. It has been there since 1959 with no problems. Our slate is grey/red in color, about 1 inch thick, and looks like it came from the New York/Vermont slate mining region. Most of the pieces are about 16 inches square, but they vary in size, as I said this is rough slate. I have never seen slate installed over concrete, not saying it can't be done, but I would be concerned about cracking the slate if the subbase is too rigid.

If it were me, I would probably remove the brick and concrete, and install the stone over a standard subbase of gravel and sand. Standard installation has been covered many times on this forum, do a search and you can read all kinds of posts by knowledgeable installers.