Backerboard for Silicone Adhesion Surrounds

dodahmanDecember 16, 2012

I have just about decided to go with an Onyx Collection wall panel for a tub surround.
This is an older cast iron tub with a finished front apron wrapping around one end, so a three sided surround kit is not needed and I want the sturdy feel of a solid surface; hence the Onyx.

Installation instructions state using silicone to adhere the panels to the wall.

I have been reading forums for many days to decide on the backer wallboards. But most questions are dealing with tiles.

Onyx says "Wallboard Options: Onyx Panels can be installed onto sheetrock (water resistant sheetrock is preferred), HardiBacker, concrete board, and any similar wallboard material.
Priming or painting the wallboard will often help the silicone adhere, especially if the wallboard is "dusty" by nature."

I am tentatively ruling out Hardieboard and CBU because of posible dust contamination of the silicone.

I am leaning towards something in the Georgia-Pacific Dens� Gypsum Boards. My main reason for this choice is because of the fiberglass mat covering.

It seems to me the best surface for GOOD silicone adhesion. Any disagreements on this point?

But I am confused by whether I need:

DensShield (tile backer)

DensGuard (tile backer)

DensArmour(green-board replacement)

Any and all thoughts and comments are appreciated. Especially concerning the adhesion of solid surface to backer-boards.


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Silicone will adhere to just about anything with great force. You don't need to overthink this or overspend on the subsurface. Plain drywall was used for years with zero problems. The problems with any sheet surface for a wet area come where the seams are. And where the top caulking usually fails. There is where the corner bead of caulk needs to adhere tightly. And that's on top of the surface, in the corners, not underneath it. So, choose whatever you want for the substrate, but be sure the corners are clean, and that you use a new tube of caulk for the corner beads.

    Bookmark   December 16, 2012 at 12:47PM
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Thanks, GD
LOL, my better half would agree with the "overthinking" part about me.
We've had mold problems before in this bathroom and GP lists the dens-family of stuff as "Highest score on mold resistance test".
As of right now I'll see what's available locally (rural area)and try to decide.
Thanks for answering.

    Bookmark   December 16, 2012 at 3:59PM
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