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Posted By Gooserider,
Sep 11, 2007 at 7:42 PM
you got a point there Fred....I've had blue balls before but never purple......lol.....
Thanks BeGreen......I like using the Durock, esp. for any veneer job I am doing, but wasn't sure about that stuff....the stuff I bought two years ago did not have perlite in it.....did they recently start putting it in the board?......
Not saying that I recommend this (I'll say it again, DO NOT DO IT), but my buddy who's an oaf has a 30 and destroyed his baffle boards. Rather than cough up the 120 bux or so for 2 new ones, he went out and bought a sheet of next gen durorock. He cuts them and uses them in place of the factory baffle. He puts a new set in at the beginning of winter, and changes it out once during the winter. 2 sets get his stove through an entire season. He burns about 5 cord of wood through his 30. The wood stove is his only heat.
If it can survive for months IN a stove, I have no concerns placing it under one.
Pen I have read on this forum different guys who do that......and I will +1 on what you said...DON'T DO IT.......if for nothing else, say those boards fail in the middle of the night and next thing you know your stove top is exposed to full heat from the fire, then warps all to hell.....but like you said, if it can withstand heat like that, surely it is good enough for the underlayment or for the surround....
Durock has no combustible ingredients.
Portland Cement <50
Fly Ash <50
Expanded Clay Aggregate <30
Or Expanded Shale Blend of Proprietary Mineral Based Ingredients <20
Fiber Glass Scrim <5
Crystalline Silica <5
The warehouses started emptying out of the old pure cement board products last year. To my knowledge they are no longer available unless found in the dusty recesses of a quiet lumber yard. Hardibacker may be fine, but I'm reticent to recommend it because it has cellulose mixed in. The competing product made by USG is Fiberock which specifically says to not use the product in high temp locations.
As you have noted, this discussion is as old as Elk from days before this forum started. It comes up annually and has been confused by the NextGen products. We do the best we can to investigate and respond based on the current market options. There is only one agenda here and that is to help others to make their installations safe and functional. If the recommendation seems narrow, it is because the answer speaks not just to a single installation, but to the hundreds that will read the thread later on.
Well spoken BG. I really comes down to the fact that the Nexgen Durock has NOT been tested in the USA for hearth applications. That doesn't mean it is not the proper product, it just has not been tested for it in the US (it HAS been tested in Canada, an meets their requirements)
And it is the exact same product, manufactured in the US in the same factory and shipped to Canada. (I was told by USG)
Does anyone have new info on Durock nex gen vs permabase
They seem to be a very similar product with similar ingredients. National Gypsum lists the lightening ingredient in Permabase as pozzolan which is volcanic tuff.
From the Woodstock Web Site,
Technical Note: Conductivity
Cement backer board is an ideal material for a hearth pad because of
its low “k”, or conductivity value. Conductivity is the ability to conduct
heat. The lower the “K” factor, the less heat is conducted through
the material. For example, Durock has a k-value of 1.92 per inch, as
compared to the k-value of common brick, which is 5.00 per inch, or
marble, which has a k-value of 15.00 to 20.00 per inch.
So I put 1" of next gen under my tile. Passed inspection here in Michigan no problem.