Let me make sure I have this correct. I am installing over hardiboard, outdoors (outside bar). 1)scratch coat of type S morter, 1/2" thick (i assume I can go into home-lowes and ask for type S morter, and they can set me up?) 2)Let the above dry. 3)then butter back of each stone and press into position. 4)after it's all done, go back with morter and grout. My question is, couldn't I combine 3 and 4, and grout as I go? It is my understanding since "fake" stone is so light, I do not need metal lathe over the hardi-board?

We are planning our exposed aggregate stair pour and just want to confirm the process. Obviously, it will change with temp and mix but overall we just want to make sure we have the right jist. We will spray inside of forms with vertical retarder before pour. After concrete has set up we will spray surface with a horizontal retarder. Wait four hours and wash/broom lightly. However, the forms will have to wait 24 hrs to be striped so as not to pull out chunks and to let vertical retarder activate? Then wash/broom. Does this sound right? Will the water from washing the surface after 4 hours compromise the inside of the forms? Please let me know what you think...... Cheers!