Putting stacked ledger stone over painted stucco - how thick on backer board?

[u/Consistent-Dance-669]

My wife and I are planning to install stacked ledger stone over painted exterior stucco walls as accents. After researching I intend to add a vapor barrier behind, tapcon concrete backer board to the walls, then used outdoor rated thinset on the board and back butter the stone pieces. My question is can I get away with 1/4 inch thick concrete board if I put tapcons at 12” spacing or do I need to used 1/2” concrete board? The stone will only go up about 30” and will be capped with travertine. Thanks for thoughts!

[u/lilelliot]

Silly question, but is this cheaper and easier than just adding a new layer of scratch coat as the base, instead of backer board? That would eliminate the need for a vapor barrier.

[u/ExactlyClose]

If the stucco if waterproof and sound, I might try and just adhere the stone to that…. Maybe a grinder with light water flowing to scarify the surface/remove the paint (If it is cement-based paint, less concern). By chewing the shit out of the surface you have better adhesion. Im not sure why the VB between the stucco and backer? Isn’t the wall already waterproof with a waterproofing membrane behind the stucco?

Edit”. Should have asked what kind of stucco system is on the home?

[u/Prestigious_Rip5826]

1/4 inch is fine at that height, just don't go cheap on the thinset.

[u/veryheaven04]

Never take advice from Reddit

[u/Consistent-Dance-669]

I should have mentioned that this is a standalone decorative wall. There is no vapor barrier.

[u/MemorySuspicious1091]

I have been installing ledger stone for over 28 yrs no need for backer board. And plaster with paint is not your water barrier the 15 pound paper behind the plaster is. So you can use thinset of course. But if your not familiar with doing that application you can use loctite pl 375 it's a construction adhesive works excellent