Vertical Granite Slab Substrate

hirayama

Working on a bathrm/shower which will have full height granite slab panels on all walls. The ceiling ht is 8ft. The owner wants the panels to be as big as possible with as few joints as possible. In some areas the panels will be as wide as we can possibly get the stone.

1. Is 7/16" Hardie-backer an acceptable backerboard to adhere the granite slabs to? For this size panels do they need to be mechanically attached?

2. Is taping the backer board joints as described in the product installation guide necessary? I thought maybe you could just apply a continuos bead of silicone between panels since it will be covered by stone panels.

3. The existing framing is 22 ga. metal studs. Are those typical backerboard screws (the ones with the wide heads) acceptable for this gauge metal stud?

4. What is the ideal thickness for the granite slab panels? 3/4"?

5. Should the backs of the stone panels be treated in any special way to promote better adhesion?

Any advice would be greatly appreciated.