Hearth question

[gnatboy911]

So after a lot of research, I think I've decided on an Englander nc13. One big downfall I found for the stove is the high r-value needed for the hearth. It requires an r-value of 2. I've read a lot of archived posts on here and think I've formulated a plan for the hearth. I wanted to run it by you guys and see if I was overlooking something.

Micore seems like a great product with high r-value, but I can't find it locally. 113 bucks from efireplace.com for (4) 2x4 ft sheets. Sorta spendy.

Researched paperless drywall. Only found one place near me that carries something similar. Product is made by American Gypsum and is called M-Glass. It is 5/8 inch thick, has an r-value of .61 and comes in 4x8 sheets for about 25 bucks.

My plan was to frame in a base using 2x4's. Then alternate layers of Durock, and the M-Glass.

2/4 framing
M-glass r-value .61
Durock r-value .39
M-glass r-value .61
Durock r-value .39
tile/stone of some kind. (haven't decided yet)

Excluding the top later of tile/stone, this would give me an r-value of right at 2.

Here is a link to the info about the m-glass (broken link removed to http://www.americangypsum.com/data/products/M-Glass%20Exterior%20Sheathing%20submittal.pdf)

Please chime in with any tips and suggestions you may have. This is the first hearth I have built, so I'm all ears.
Thank you!

 

[rwhite]

I can only offer a suggestion on Micore. I did some research and found that office cubicle walls are constructed of micore (not all of them). I found some at a used building supply store for $5. Ended up with 2 5x8 sheets. Might be worth checking out. Otherwise to find it it like looking for flea hair.

I'm no engineer by far, but I think that even with what you propose you'll still need some sheathing (5/8 or 3/4) under it all. I'm not sure that gypsum and durock will hold a stove unsupported. I may be wrong as I have never dealt with 4 layers of it.

Another thought... figure out what the extra Rvalue will cost and compare stoves. The NC 30 is about $150 more and only requires 1.5 R value . If it's gonna cost $50-75 to get that extra .5 then maybe you can upgrade for not much more.

 

[begreen]

The plan sounds like it should work though I know nothing about the m-glass product other than what is provided on the product brochure.

Or consider the Englander Madison or the True North TN20. Both have an ember protection only hearth requirement.
(broken link removed to http://www.amfmenergy.com/50masmheup18.html)

 

[Simonkenton]

rwhite is right! You must put a substantial subfloor under the mglass and durock. The specs for laying tile are 1 and 1/8 inches of plywood and you certainly need as much for stone and a wood stove.
So, on top of the 2x4s, 3/4 plywood topped with 1/2 plywood, then the mglass and durock.

 

[gnatboy911]

rwhite is right! You must put a substantial subfloor under the mglass and durock. The specs for laying tile are 1 and 1/8 inches of plywood and you certainly need as much for stone and a wood stove.
So, on top of the 2x4s, 3/4 plywood topped with 1/2 plywood, then the mglass and durock.

Thank you guys for the suggestions....not sure why I overlooked the plywood! oy...that would have been a mess.