# Installing stone on Durock around fireplace



## Guap0_ (Dec 2, 2017)

If you can verify that the unmodified thinset doesn't outgas, use it. That is most important.


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## Canarywood1 (May 5, 2012)

They are both covering their a$$, use some common sense.


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## chandler48 (Jun 5, 2017)

I wouldn't use Durock NOR thinset to set rocks on a fireplace. OSB outside the 2" limit barrier, tarpaper and lath with a sand mix cement makes a much better adhesion method. Now if you are talking the lightweight faux stone, then modified thinset is fine. Your fireplace will not heat up the Durock nor the thinset to a point of "off gassing".


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## Guap0_ (Dec 2, 2017)

Demand their product data sheets. There is a name for them but I can't think of it now.


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## Nealtw (Jun 22, 2017)

chandler48 said:


> I wouldn't use Durock NOR thinset to set rocks on a fireplace. OSB outside the 2" limit barrier, tarpaper and lath with a sand mix cement makes a much better adhesion method. Now if you are talking the lightweight faux stone, then modified thinset is fine. Your fireplace will not heat up the Durock nor the thinset to a point of "off gassing".


 Depending on design and BTU, some times that no wood limit is up to 7 inches.


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## chandler48 (Jun 5, 2017)

Yeah, but I figured it was a gas unit with less box heat. Most wood burning units, definitely adhere to stand off limits.


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## Nealtw (Jun 22, 2017)

chandler48 said:


> Yeah, but I figured it was a gas unit with less box heat. Most wood burning units, definitely adhere to stand off limits.


All I have ever framed around has been gas. they have those triangle steel things on top to designate distance to wood. Offsets


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## chandler48 (Jun 5, 2017)

This one was wood burning, so we used wider Durock to space from combustibles. Rock guy insisted on OSB for the rest.


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## jtech1 (Aug 17, 2017)

Thanks, everyone! This is faux stone. Eldorado Mountain Ledge. Manufacturer recommends cement board. Non-combustable area is right up to unit on sides and about 4-5" on top (metal standoffs). I am considering using unmodified thinset for the border course immediately around the fireplace (6" sides, 8" top), and then modified thinset for the rest of the install. What I really want to find is temperature ratings on thinset and also temperature averages above fireplace, but can't find either. I am sure they get tested.


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## chandler48 (Jun 5, 2017)

Remember combustibles include wood framing, so all your adjacent framing will need to be of metal studs, then Durock. I think your worries about the modified thinset are not founded. I have never heard of Off gassing of thinset. When it is cured it is basically concrete. It won't melt and won't turn to slop. 

If that weren't the case, you would be finding article after article disdaining the use of it in such a situation. Since you can't find it, use the modified thinset for the entire project and move on.


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## jtech1 (Aug 17, 2017)

Thanks... that is how I was leaning on the modified.

My wood framing is all outside the non-combustable area... and I actually wrapped the inside face, back wall and framing above with durock, even though not required.


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## jtech1 (Aug 17, 2017)

On the same topic... has anyone here used Eldorado Mountain ledge before? I'd like to know if there is any cutting necessary to get good joints in drystack so you don't see glaring gaps like I see on some commercial jobs on the outside of buildings... where it looks like they just slapped it all up and nothing is level or straight...


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## stadry (Jun 20, 2009)

*that's commercial work & folks just walk by,,, its not your $ either,,, very much different if you're in the recliner & have to look at it every day*


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## jtech1 (Aug 17, 2017)

Yeah... big gaps... non-tinted mortar... BAD cuts... wavy lines...

I have never done stacked stone before, so I am trying to find a video or tips online to help me not make some of those mistakes.

As for cutting Eldorado Mountain Ledge... I know I will be end cutting it and trying to hide those cuts... but length wise, I am curious if I should be able to get things fitting tight by finding the right pieces, or if I will likely need to chip off part of most stones to get them to fit. Eldorado makes color touch up kits, since the color is only on the surface and cutting exposes non finished edges. Not sure if the color kits actually work well or not.

Also, I had one mason tell me that he does all cuts dry since using a wet saw will keep the stone from sticking properly... but I see some installation instruction that recommend wetting the wall and stone before applying the thinset. Any reason I cant use my wet saw for the cuts?


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## stadry (Jun 20, 2009)

*we cut dry too,,, use your wet cut saw - just don't add wtr,,, we have a vac hooked up to ours*


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