I am making a custom shower, planning to cut my own stone slabs from stones found in my area. They will be granite, quartz, some others, that I cut with my own saw. I'm wondering how to attach the stones to backerboard so that the assembly is waterproof. The pan will be thin concrete over backerboard as well. Considering attaching expanded metal to backerboard with a 1-2mm gap and then using standard thinset buttered to back of stone then setting to wall. But then how to waterproof the assembly?
How to Attach Natural Stone to Backerboard in a Shower
backer-boardshowerstonethinset
Best Answer
What you are doing sounds like you could simply use modified thinset. If the tile will be uniform, or perhaps not you could use tile setters shims to create the joints and then use sanded grout to fill the joints. You could use epoxy grout, I never have in a shower stall, but I am sure it would work.
As far as waterproofing goes starting with the floor pan, I have never seen backer board used on the floor. I have seen ready made bases that will accept tile, I have set a sloped sub base and installed PVC liner with a dry pack mud bed over that with cement board on the walls only, and then painted the walls and floor with a roll on membrane. After that, tile is set and grouted.