I am installing a single step off of my deck. I have laid a concrete pad and selected cast concrete stones for the riser. I plan on having two layers of stone and then capping with a solid granite tread. My question is - should I allow the mortar between the riser levels harden before installing the tread on top? This monster of a tread is over 200 lbs and I am concerned that if the lower portions are not hardened that it may sink and possibly fall out of level and be too low.
