Natural stone patio over existing concrete pad (bomb shelter)
So we bought a house with a huge concrete bomb shelter under the backyard. We have a lannon stone wall I am disassembling. I will be using that white field/ lannon stone to build a natural stone patio over the bomb shelter. The exposed portion of the bomb shelter is a big concrete slab level with the rest of the grass backyard. I'll post a picture when I get home. I've read that you can attach the stones right to concrete with mortar, then you can mortar in between the stones for a tight fit. My concern is cracking. We live in Wisconsin and even though the bomb shelter is like 25 feet deep/ thick of concrete I am sure it will expand and contract between winter and summer. Should I attach the stones to the concrete with mortar then fill the joints with crushed stone or dirt? Sand? Should I build up a layer of compacted gravel and sand then float the stones on top of that? That seems like a waste right? We already have a nice base. I just don't know what to put between the stones we mortar onto the concrete. I think my wife wants dirt in the joints so we can try to grow grass or moss between the stones.