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Sep 15, 2019
Allegany, NY
I'm installing a hearth pad and a wall barrier for my new (old) Vermont Castings and have been unable to find answers to a couple of questions.

For the pad, I plan on using 1/2" Durock or Hardie board on top of 1/2 or 3/4" plywood or OSB on a 2X6 frame. I've read that you should use mortar and screws to bond the backer board to the plywood. Why both? Wouldn't screws conduct heat to the plywood? Maybe I should use the screws like clamps and then remove them when the mortar has set. Or, if the conductivity of the screws isn't an issue, why bother with the mortar at all? Any thoughts?

For the wall protection, I intend to screw backer board to 1" furring strips made from two strips of backer board attached at the wall joists. That will then be covered with tile or stone laminate or something else. The manual and some discussion boards say not to put the spacers directly behind the stove, but my installation is in a corner. So where would the spacers (furring strips in my case) go? Maybe the board should be applied with glue and then (as I suggested above) "clamped" with screws, which I would remove afterward.
The plan is good. I would use 1/2" plywood with 2 layers of Durock NexGen to raise the hearth R value. The wall shield plan is good. Be sure to leave a 1" gap at the bottom and open at the top so that air can freely convect behind the panels. Personally I am not too worried about the strips or screws behind the stove. It is a pinprick of heat and the tile on top will diffuse any direct heat.