I have been asked to overlay a set of concrete steps with square cut blue stone. The concrete is in good condition, and there is a 4'x14' walkway, two steps that are 9' wide, and then a landing that is about 3.5'x9'. I am assuming that the concrete should be washed with acid before laying the mortar bed. If my stone is 1" thick, how much of a bed do I need at the thinest point. I know that I have to make sure it drains, but how thin can I go? Will type N work for the bed, and then filling the joints? Go you typically wait a day before going back and doing the joints? any help would be great.