Wonderboard over sheetrock?

[sevenbak]

I am installing a corner hearth. My stove rated clearances are met, but I still want to tile the wall behind. Can I tack wonder board to the studs but over the existing sheetrock? Are there any problems doing this, and if not, do I need to use thinset between the sheetrock and wonderboard for added stability?

Thanks for any help!!

 

[begreen]

It should be fine. The wonderboard in this case is just acting as a backerboard for the tile. I wouldn't put thinset between the sheetrock and cement board.

 

[sevenbak]

Thanks a lot. But why no thinset between the layers? Would it not act as an extra layer of uncombustables, as well as make the wonderboard more stable for the tile?

 

[littlecleo]

As Begreen said you should be fine just attaching the CBU over the sheetrock, just make sure and fasten your cbu screws directly into the studs, and not just sheetrock. If it makes you feel better, it won't hurt to put thinset between the cbu & sheetrock, I would use a modified thinset, and a 1/4" trowel.

 

[sevenbak]

Thanks, I think I will do as suggested and forgo the thinset between layers. This noob appreciates all the help!

 

[wood-fan-atic]

I'm not sure why you wouldn't just REPLACE the sheetrock with wonderboard? Thats what I would do -- not right or wrong -- just MHO.

 

[begreen]

Thanks a lot. But why no thinset between the layers? Would it not act as an extra layer of uncombustables, as well as make the wonderboard more stable for the tile?

No, the extra layer would be a trivial difference. But the main reason is that the paper on the sheetrock is not meant for this. Regular sheetrock is not meant or designed to have a layer of wet mortar applied. If there was greenboard maybe, but not with regular sheetrock.

 

[btuser]

Just read the directions. I'm sure you can go over the drywall, and there's not much of a difference in cost between 1/4" and 1/2". I think the 1/2" is so you can avoid a layer of drywall in the first place. I don't think you need a decoupling layer on walls like you do on floors, but depending on your grout lines and the heat coming from the stove you may want to just trowel on a layer on thinset and attach 1/4" wonderboard to the drywall only, not screwing through into the studs. That way your tiles will not be tied to the structure and be suceptible to cracking and frame movement (but I'm talking more about floors, my own unfortunately!).

 

[sevenbak]

Thanks all, for your advice on this. I used thinset on the floor under the wonderboard, but just used screws on the walls.