Another Hearth Pad Building Question

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TNCave

Member
Feb 4, 2009
55
TN
Hello Again,

I'm having no luck finding Micore locally.
I decided to just stack up Durock to attain a proper R-value, but upon arriving at Lowe's I was dismayed to discover they only carry it in 3x5, making my 4'x4' with a cut corner front, a pretty difficult shape to attain. Being Sunday, they couldn't even tell me if they could order 4x8, although I'm assuming they can as it has a part number on the website.

Looking online, I found Permabase brand cement board in 4x8 at Home Depot just an hour away. Their website claims an R value of .2 for 1/2" thick Permabase.
Does anyone know if this is an adequate substitute for Durock?
One fear is the weight of it, Home Depot's website claims 99lbs per 4x8 sheet.

Any help would be great.

Cory
 
Where are you located at in Tennesse ? They sell it here in the Louisville, KY area at Nexgen. There is also a Bowling Green location which is about an hour from Nashville if your anywhere near there.
 
I'm near Cookville, TN, about 2 hours from any urban area.
Bowling Green actually isn't too far, just over an hour I'd guess.
 
Here's there info, give em a call, and make sure they have what your wanting. Even if you do end up going up, and buying the Micore you will still need to use a layer of Durock since the micore is very soft, and brittle. I used 2 layers of Micore, and 2 layers of durock on my pad alternating layers. I'm not sure if you are aware that Durock can easily be cut with a razor knife ?

419 State St.
Bowling Green, KY 42101
Phone: (270) 846-2556
Fax: (270) 846-2560
Contact: Kenny Duvall
[email protected]
 
I also live in tennessee (west) and I just finished a hearth pad and also had a very difficult time finding micore.I ended up purchasing some from e-bay,it was a little more expensive but It was delivered in two days.Also i could not find any durock in all the local lowes and home depots.All they had was the new generation stuff which is not approved for hearths.I ended up finding some wonderboard in Paris Tenn at a mom and pop hardware store.
 
Does the Durock next generation does not have the same R value/heat transfer as original Durock?
 
I do not know what the r value of the next gereration durock is.All I know is it is not been approved for hearths.I guess it is the materials it is made from.It is a lot lighter in weight.
 
traveler659 said:
I do not know what the r value of the next gereration durock is.All I know is it is not been approved for hearths.I guess it is the materials it is made from.It is a lot lighter in weight.
Click to expand...

I have heard this also, and from my research I do not find this to be the truth. USG's product info pdf on Durock NexGen states it is non-combustiable, and suitable for fire place fronts. Maybe some others can chime in on this ?? PDF link below....

http://www.usg.com/rc/data-submittal-sheets/panels/durock/durock-cement-board-submittal-CB399.pdf
 
Interesting thread . . . and I've been meaning to post some info I dug up a week or so ago on hearth construction. Here's what I found when I talked to folks in the various companies . . . if anyone else can contribute something to this thread and support or refute my findings I would love to hear from them.

This started after a discussion was held here about the NextGen Durock no longer having the UL-listed for floor protection for hearths sticker on it . . . and so I decided to do some digging and find out what folks could use for a hearth.

Durock: The guy I spoke with -- sounded like it was one of their tech folks and not the run-of-the-mill salespeople -- said the NextGen Durock is pretty much the same as the old stuff only it is lighter thanks to perlite which is not combustible. He added that the product is pretty much the same, but the company did not do any new tests on the product to get the UL sticker (why . . . I don't know.) He said it is rated to take up to 200 degrees F heat and has a R value of .26 (1/2 inch) . . . and then he added a kicker . . . he said while the old stuff had a UL sticker on it for use as floor protection for hearths he said the old stuff and the new stuff is not allowed or designed to meet that UL spec by itself, but rather it is intended to be "part of an assembly."

Wonderboard: The person I spoke with here said the 1/2 Wonderboard is listed, but said that it is not specifically listed for use for fireplaces or woodstoves. The person continued by saying it has a one hour fire rating and a R value of .20 and a 200 degree F heat limit (due to the mesh in the product melting at that temp) and that they would not recommend using this product inside a firebox.

Hardiboard (Hardibacker 500): I spoke with another tech and much like the Durock tech he said the product is not designed for use as a hearth by itself, but it could be covered with tile or brick and be used as "part of an assembly" for floor protection. He added that there is no R value protection since the product transfers heat . . . although to be truthful I was a bit surprised and skeptical when he said this. . .

So after all this . . . I am more confused than ever . . .

If anyone would care to support/refute anything:

Durock: 1-800-USG-4YOU
Wonderboard: 1-800-272-8786
Hardiboard: 1-888-542-7343

At this point the Inspector and I are thinking that the original Durock was listed for use as floor protection . . . but it may have been due to its ember-resistant qualities vs. the R value property. We also believe that none of the three current products truly offer UL listed floor protection for use as a hearth by itself (and perhaps the only true UL listed floor protection are the pre-made hearths which have been tested) . . . but that any of the three products may be used to build safe hearths providing they are covered with tile/stone/etc. as this seems to meet the "part of an assembly" mentioned by the tech guys in two of the three places.

Thoughts???
 
firefighterjake said:
Interesting thread . . . and I've been meaning to post some info I dug up a week or so ago on hearth construction. Here's what I found when I talked to folks in the various companies . . . if anyone else can contribute something to this thread and support or refute my findings I would love to hear from them.

This started after a discussion was held here about the NextGen Durock no longer having the UL-listed for floor protection for hearths sticker on it . . . and so I decided to do some digging and find out what folks could use for a hearth.

Durock: The guy I spoke with -- sounded like it was one of their tech folks and not the run-of-the-mill salespeople -- said the NextGen Durock is pretty much the same as the old stuff only it is lighter thanks to perlite which is not combustible. He added that the product is pretty much the same, but the company did not do any new tests on the product to get the UL sticker (why . . . I don't know.) He said it is rated to take up to 200 degrees F heat and has a R value of .26 (1/2 inch) . . . and then he added a kicker . . . he said while the old stuff had a UL sticker on it for use as floor protection for hearths he said the old stuff and the new stuff is not allowed or designed to meet that UL spec by itself, but rather it is intended to be "part of an assembly."

Wonderboard: The person I spoke with here said the 1/2 Wonderboard is listed, but said that it is not specifically listed for use for fireplaces or woodstoves. The person continued by saying it has a one hour fire rating and a R value of .20 and a 200 degree F heat limit (due to the mesh in the product melting at that temp) and that they would not recommend using this product inside a firebox.

Hardiboard (Hardibacker 500): I spoke with another tech and much like the Durock tech he said the product is not designed for use as a hearth by itself, but it could be covered with tile or brick and be used as "part of an assembly" for floor protection. He added that there is no R value protection since the product transfers heat . . . although to be truthful I was a bit surprised and skeptical when he said this. . .

So after all this . . . I am more confused than ever . . .

If anyone would care to support/refute anything:

Durock: 1-800-USG-4YOU
Wonderboard: 1-800-272-8786
Hardiboard: 1-888-542-7343

At this point the Inspector and I are thinking that the original Durock was listed for use as floor protection . . . but it may have been due to its ember-resistant qualities vs. the R value property. We also believe that none of the three current products truly offer UL listed floor protection for use as a hearth by itself (and perhaps the only true UL listed floor protection are the pre-made hearths which have been tested) . . . but that any of the three products may be used to build safe hearths providing they are covered with tile/stone/etc. as this seems to meet the "part of an assembly" mentioned by the tech guys in two of the three places.

Thoughts???
Click to expand...

I have been thinking about this since I recently installed a tile floor for my new Jotul Oslo to sit on. I read the instruction manual prior to purchasing and interpreted that you only need some sort of non-combustible floor for protection. I went ahead and installed 1/4" hardibacker and porcelain tile on a section of the floor which is about 5' X 10'. From doing research afterward I found this might not be adequate for all stoves, but should be fine for the Oslo. Especially since people are saying hardibacker is a thermal conductor. This lead me to another thought.

Instead of worrying about the insulation aspect of the hearth, what about a heat sink design? Basically taking the radiant heat from the bottom of the stove and distributing it over a large area to prevent any one spot from getting too hot. I have no idea of the types of materials and size of hearth we would be talking though.

Chris
 
I may have over exceeded my stoves R value requirement when building my hearth, but I figured that was Ok. My Englander 30 has a 1.5 R value, and I used 2 layers of Micore, and 2 layers of Durock in alternating layers. The top of my hearth is also covered in 2 3/4" thick stone so I think I should be good. We are still finishing up the install so I can't comment on how well it works, but we sure are looking forward to it :)
 
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