Hearth pad, hearth board...etc...

[suprz]

My Jotul tdic came with a "hearth pad" i dont know if the owner built it, but i can tell you that it has at least a 1 1/2 inch thick piece of plywwood covered with cement board, then covered with tile. It must be around 3-4 inches thick. It is heavy as all h3ll too! My wife wants to build our own instead of using this one, which is ok with me! My question is that i cannot find what R value my stove requires underneath it during operation, and how to calculate the r value of a 1/4 inch piece of plywood and standard cement board (durorock?) and tile would be. I want it to be thin, but safe.

I have all the tools to build it, just dont know what the minimum thickness can be and the best materials to use

 

[begreen]

You'll want a stiffer piece of plywood to mount the Durock NexGen to for a stable tile base. I would use 3/4". 1/2" Durock NexGen is r=.39, regular cement board is R=.26

Here's a good table of common materials R value.

http://www.chimneysweeponline.com/horvalue.htm

 

[firefighterjake]

http://www.jotul.com/FileArchive/Fi...s and inserts manuals/Jotul_ 3TDIC_2_0394.pdf

If I am reading this right . . . and this is your stove, it appears as though there is no actual number for the R value . . . or at least they do not give a set number . .. but they do require Durock or a cement board of similar construction at least 3/8 inch thick and then you can put tile, stone, etc. on top of that if you so choose . . . or you can go with the pre-made hearth if it has a safety mark such as UL or FM. Of course the hearth must also be 18 inches in front of the stove and 8 inches along the sides and back and be a minimum of 38 x 43 inches. See Page 5.

As BG mentioned there is a great chart showing the R values . . . and also as he suggested you will want something thicker than 1/4 inch plywood to mount your tile/stone, etc.if using plywood as you don't want any flexing. I also think you'll find that plywood in itself does not offer much in the way of R-value since it is combustible.

 

[suprz]

Well, the wife (or as i call her...THE BOSS) wants me to build the hearth for the stove. We are thinking of the 38x43 dimensions, and i will use 1/2 ply and 1/2 Durorock next gen and tile. We are thinking about using the tiles that look like river rocks, but i have concerns about the feet of the stove and the stove wiggling. Thie hearth will be going on top of oak flooring. And according to what i have read and the chimney installers / stove installers. That should be plenty of R value for the floor. Now to go look for tiles.. Oh yeah... My local Lowes only has durorock next gen in 36 x 60 sheets, so i guess i will have to get 2 sheets and i have to get a permit for the chimney install that is happening on 10/29

 

[begreen]

Go 3/4" plywood. The cost difference is negligible but the rigidity is substantially more. Or double up on the Durock NexGen layers.