I am going to install various shapes and sizes of 1 inch minus slate tile on a 12 inch thick exterior concrete slab. The slab is covered under an entry roof, is well cured, level but rough, has no expansion joints (probably because it is so thick) and is located in a relatively extreme climate with maximum temperatures ranging from -20F to +95F. Please advise me the best product to use for adhering and levelling the slate on the concrete and also the best mortar/grout to use for the joints between tiles. How wide should the joints be and also please provide me any tips you have for this type of installation because this will be the first time I have installed slate on exterior concrete.

Rick, I've taken a read of your post over the last few days and have not responded until now. Let me start with your slab is likely not 12". No one I've worked with would pour a 12" slab unless they planned to put up an oil drilling rig. You probably have a 4" or %' slab with a 12 ' curb. That being said I have installed porcelein tiles on an exterior slab with fairly good success but never have done slate. Here is a link to some folks who may be of assistance Slate Paving,Paving Stones Suppliers,Slate Stone Paving,Paving Stones Exporters,Paving Slate Stones Check out their site and see if they can give you advice on how to do your patio. Good luck, Bob