Looking for hearth pad ideas.

[chris-mcpherson]

tiber...Your right...I meant two layers of 1/2" Micore.
I may be splitting hairs but according to the hearth.com link I found, 1" Micore will be R 2.33.
fossil...I'm not gonna even consider the sub floor for it's R value.

 

[bobforsaken]

If it were me I'd do 1/2 inch Micore300 topped with a quarter inch hardibacker and some mortar and tiles of choice. The hearth would end up about and 1.25 to 1.5 inches thick.

 

[VTHC]

I agree about the air with one caveat: The air has to flow under the hearth. The "dead air" arument I don't think holds water and that's why the "wall shields" portion of the code indicates that "at least 50% of 1 inch below and above the wall shields is open for air flow".

Actually the R value I quoted was for horizontal dead air space (much like a sealed double pane window). If the space is vented the R value increases to 1.43. Dead-air space is a valid method for increasing R value, it is used in double and triple pane windows. In a vertical setting the air flow allows for a greater R value, thus tighter clearances.

 

[begreen]

If it were me I'd do 1/2 inch Micore300 topped with a quarter inch hardibacker and some mortar and tiles of choice. The hearth would end up about and 1.25 to 1.5 inches thick.

Go for 1/2" cement board for increased rigidity. You don't want this stuff flexing.

 

[begreen]

Hope not. That's wallboard!

It's not "wallboard" as in "plain vanilla gypsum covered in paper", he's doing the right thing in my opinion, and yes I used it.

Yeah, gold bond is the top of the line fire stuff (exceeds "type x"). However type X is a designation whereas Gold Bond is a brand which exceeds Type X spec. It's got little fibers in it which make it a real PITA to cut, have a drywall blade and a razor ready and cut whatever fibers bind up the drywall saw.

All about the fire standards and gypsum products:
http://www.nationalgypsum.com/resources/faqs/gypboard.aspx
http://www.nationalgypsum.com/resources/safetyinformation/

Keep in mind you still have to meet the surface requirement for nonflammable which gives you a nonflammable assembly for a given R value.

EDIT: Micore 300 has a staggering R=1.03 for a half inch. Per the spec sheet ( http://literature.usg.com/pdf/IW803.pdf ) it still has to be covered in noncombustable material.

This is fire-resistant wall board. My understanding is that this is not suitable for a hearth and it should not be recommended. Unlike cement board this has a paper backing and is not as stiff. Nor should a plywood substrate be considered as part of the insulation value for a hearth because it is combustible. Please be careful about what is being suggested as appropriate hearth and wall shield materials.

 

[firefighterjake]

So far of all the ideas put forth from a fire safety standpoint I really like the idea of using metal studs and utilizing the dead air space as mentioned by VHTC . . . and going with a more rigid and listed material such as 1-2 layers of 1/2 Durock on top . . . then again when it comes to having a fire burning at 600-900 degrees 24/7 in my home I want to be sure I'm meeting and exceeding what is required.

I'm not sure I like the idea of using wallboard . . . I have seen that there is a difference between fire resistant and fire proof. Also, as BeGreen mentioned I have yet to find any wallboard that is as hard and inflexible as Durock or similar products.

On another note . . . I may have missed this part . . . is Durock still making their listed 1/2 inch cement backer boards? I know Durock was producing a new 1/2 product that supposedly would not be listed for hearth protection . . . and I thought there was a discussion a while back about Hardiboard having styrofoam beads embedded in it to make it lighter.

 

[VTHC]

On another note . . . I may have missed this part . . . is Durock still making their listed 1/2 inch cement backer boards? I know Durock was producing a new 1/2 product that supposedly would not be listed for hearth protection . . . and I thought there was a discussion a while back about Hardiboard having styrofoam beads embedded in it to make it lighter.

Good question Jake... The old Durock was listed, but the new "NextGen" doesn't seem to be. I used the older version on my hearthpad, and i only had to double it up over my floor (no air gap). Their web site eludes to it being "Fire rated" and "Fire Class A" but there is no UL testing data that i could find: http://www.usg.com/durock-cement-board.html#tab-features

My only concern would be the structural dead load on the durock. Not sure if someone can use it to span a gap. Maybe a layer of plywood may be necessary, but then you run into the combustible issue... If you set the studs 12" O.C. and use 2 layers would that suffice?

 

[begreen]

I would use 2 layers of cement board on studs set 12" apart to support a stove. If you want to give it extra strength between the studs, pop-rivet a skin of sheet metal to the studs before attaching the durock.

 

[VTHC]

I would use 2 layers of cement board on studs set 12" apart to support a stove. If you want to give it extra strength between the studs, pop-rivet a skin of sheet metal to the studs before attaching the durock.

Ooooh perfect! didn't even think of that. Use something like a 16ga. piece of sheet metal... you wouldn't even have to pop-rivet it - just fasten the Durock to the studs through the sheet metal (may have to pre-drill the metal).

Well, i think we built a pretty fine elevated hearth pad for the OP!

 

[chris-mcpherson]

I think I found a local supplier for the Micore product. I'm waiting on a call back on price.
Due to certain constraints, a metal stud platform probably won't be able to work.

Tell me what you think...
I'm gonna pull up the existing slate hearth pad that's too small.
put down 2 sheet of 1/2" Micore 300 for an R value of 2.33 (according to the hearth.com article I linked earlier).
Finish with stone or tile of my wifes liking.
Unless I'm figuring wrong this will give me nearly double of what is required (not counting the stone or tile).
Will this be ridged enough?
I'm not gonna do anything until I get your stamp of approval.
Again...thank you guys for your help on this.

VTHC...I spent a lot of time skiing and camping in your neck of the woods (I grew up NE NY), I love Vermont. Every once in a while my wife will come home with NY or God forbid, Canadian Maple syrup. She just doesnt seem to understand the difference with Vermont Grade A Dark Amber!

 

[tiber]

That looks good to me. I don't see anything objectionable to it so long as the micore is completely covered. Flooring is not one of the suggested applications for micore, however (more here: http://www.gypsumsolutions.com/brand.asp?prod=71 ). I would consider putting 3/8ths or better of wonderboard (or any other cement board) over it. Cement board is noncombustable, so it's a good choice anyway if you're going to put some kind of broken rock sans grout or whatever over it, but it's got poor R values so it's not suitable to use alone.

Do post the price of micore, I am curious.

 

[VTHC]

She just doesnt seem to understand the difference with Vermont Grade A Dark Amber!

Good man! Dark Amber is the way to go! Not bad for a "flatlander"! ;-)

I think you will be fine with what you described. One little caveat... can you tile over micore? You may have to add a layer of non-combustible 1/4 or 1/2" cement board for the thinset to adhere to correctly.


As many have said before me - pictures or it didn't happen!

 

[chris-mcpherson]

Watch it... :smirk: I may have a dixie zip code but I'm a Yankee to the bone!

The Micore is $45 a 4x8 sheet. I'll just need one because my hearth pad will only be 48x38 so I'll just double it over.
The retailer described it as a "fire retardent accoustical tile"...?
Get a hold of this...I have to pay the retailer and then go pick it up at the wholesaler, what a racket.
I can also pick up a sheet of 1/2" Wonder board at HD for $10 and lay that on top to put my tile on.

So...this is where I am now:
Pull up existing slate hearth
put down two layers of 1/2" Micore
put down 1 layer 1/2" Wonder board giving me a total R value of 2.6 (more than double min spec)
thin set
tile
grout
beer
pictures
Speak now or forever hold your peace.

 

[tiber]

If that's micore 300 you're getting a STEAL. I wouldn't complain too much about the trip to the wholesaler at that price. Plus you get to talk to the wholesaler who may have better prices on other materials you want for your hearth.

Yes it's normally used for acoustical walls such as cubical walls, classrooms, etc. Per the link I tossed out there, it's suggested use is for everything but flooring which is why everyone is suggesting the cement board.

It looks good. Glad you're not substituting maple syrup for thinset. With all this talk I was starting to wonder...

 

[firefighterjake]

I think I found a local supplier for the Micore product. I'm waiting on a call back on price.
Due to certain constraints, a metal stud platform probably won't be able to work.

Tell me what you think...
I'm gonna pull up the existing slate hearth pad that's too small.
put down 2 sheet of 1/2" Micore 300 for an R value of 2.33 (according to the hearth.com article I linked earlier).
Finish with stone or tile of my wifes liking.
Unless I'm figuring wrong this will give me nearly double of what is required (not counting the stone or tile).
Will this be ridged enough?
I'm not gonna do anything until I get your stamp of approval.
Again...thank you guys for your help on this.

VTHC...I spent a lot of time skiing and camping in your neck of the woods (I grew up NE NY), I love Vermont. Every once in a while my wife will come home with NY or God forbid, Canadian Maple syrup. She just doesnt seem to understand the difference with Vermont Grade A Dark Amber!

Looks pretty good to me . . . and I like your line of thought . . . the thinking that more is better when it comes to safety. As I said earlier, when it comes to fire safety I tend to exceed, rather than just meet, the standards and manufacturer's specs.

 

[chris-mcpherson]

It's good to know I'm getting a good deal on the Micore.

Thanks Jake...now that I have my stamp of approval I'll get started this weekend.
I'll make sure to take progress pics along the way.