permabase--seen both OK and not on the site

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Oct 13, 2017
Oakland, CA
I am building an alcove which will have 1" air gap convection wall covered with tile for a Lopi Patriot stove. The contractor picked up Permabase from the local lumberyard. I read here both that perm abase is OK and not Ok because of the polystyrene. Should I stop the project and have only durock or nextgen durock? Are there other products that work too? Also, what type of tile adhesive (thinset) should we use?


HI again
The more I read, the more it appears Permabase is not a good substrate for a hearth tiled wall. What led me to think there were 2 opinions was this quote "As noted in the other thread, this is not an NFPA211 wall shield because of the trapped air space. The Permabase is not the issue, it is non-combustible according to the MSDS. The issue is the non-ventilated wall." There were a couple of others too. So I will return the perm abase and use durock. We are building an alcove where there used to be a fireplace which had a Lopi Patriot inside and a stainless flue liner. We removed the fire[lace and chimney and will be framing in steel studs then covering with durock, 1" aluminum spacers going vertically up to 7', a second layer durock starting at least an inch above the floor (also durock but hopefully just one layer) and also open at the top and then thin set and tile. Even without the convection wall, we have distance to combustibles on the side for the stove but not in the back. Is there a minimum gauge for the steel framing for this? Is there anything I am forgetting? The front awl of the alcove starts at about 5.5' above the floor and will have durock and a convection wall too.

Thanks again