I wanted to screw Hardie backer board (.42") over my drywall to the steel studs to adhere 6" x 24" x1" stone ledger panels using polymer modified thin-set, floor to ceiling is 12'.

Problem is that Hardie and Durock backer board specifies 16" maximum (assuming no drywall is underneath). Problem I guess is deflection (bowing). Does anyone have any recommended practice with this kind of application?

I feel that adding construction adhesive in between the drywall and backer board along with screws to the studs should strengthen it quite a bit. Plus the ledger panels will add rigidity.

Adding 2x4' studs is not an option for me.

Thanks for your help!

  • What thickness is the sheetrock? Is this all on vertical surfaces (not horizontal like shelf/counter)?
    – wallyk
    Feb 6, 2017 at 18:25
  • What are "ledger panels"?
    – isherwood
    Feb 6, 2017 at 18:26
  • Frankly I'd be concerned with the total weight of that structure... 12' high stone wall got to weight quite a lot, I'm not sure metal studs can support that kind of weight. There are many kinds, and some of them are quite flimsy.
    – haimg
    Apr 11, 2017 at 19:18

2 Answers 2


This question is either subjective (based on opinion and personal standards of quality) or is a warranty issue. In either case it's probably off-topic. That said, here are my thoughts.

Yes, adhering the cementboard sheet to the drywall will add stiffness--probably enough to result in a satisfactory substrate, especially when considering the large size of your stones. However, it may not meet warranty requirements for either the cementboard or the stone.

All that said, tt would probably be trivial to cut out the majority of the drywall at convenient lines and replace it with half inch plywood. Glue your cementboard to that and be sure you won't have problems.


Is it feasible to step the veneered wall out from the rest of the wall a bit? I'd probably run 1" or 2" material horizontally on 12" or 16" centers. Many of the rock veneer panels have corner pieces available.

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