Can i use wood studs to build frame for hearth pad?

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Chris H

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Nov 9, 2014
21
moorseville missouri
Hi everyone! IMG_20141109_210249_468.jpg IMG_20141109_210234_418.jpg

I am a newbie, and am trying to build a raised hearth pad to place a us stove pedestal king model 2007b wood stove on.

I am somewhat confused on the K to r value thing...but with research I converted the following:

manual says to have a thermal conductivity of K=0.45 BTU in/ft. 2 hr deg F. with 28 gauge sheet metal or a UL listed floor protector..... So I read on the internet and found calculations...if I did it right the r value is 2.22...does that sound right?

So if that is right I need a hearth that is gonna be hard to build! I have read that you can use the air space under a raised hearth as an r value. One website says ventilated air space of 1" has an r value of 1.43.

Attached is 2 pics of what I have done so far...details are as follows...have wood floor..used 2x8 wood studs to make the frame for the hearth....the blue tape is the outline of the stove where it will sit on the hearth.

Any suggestions...help...?
 
Using studs to build a hearth is no different than the joists that lay underneath the floor. As long a s you have the proper r-value between the stove and any combustible material you will be fine. Your assumption that air space will have an r-value is correct but for the flooring but you will still have to meet r-values in relation to the studs.
 
Last edited:
rwhite said:
Using studs to build a hearth is no different than the joists that lay underneath the floor. As long a s you have the proper r-value between the stove and any combustible material you will be fine. Your assumption that air space will have an r-value is correct but for the flooring but you will still have to meet r-values in relation to the studs.[/quot

OK so does the r value only apply to the area of the hearth directly under the stove or the whole hearth?...reason I ask is I can get a hearth pad cheap that has an r value of 1.5...I'll add durock on top of the plywood and tile to equal an r value of 2.2....as u can see in pics ...the hearth is large... Thanks for replying!
Click to expand...
 
Chris H said:
I am planning on doing at least 2 layers of durock with metal or aluminum sheets sandwiched between durock to help dissipate the heat
Click to expand...

Durock Next Gen 1/2" has an R value of 0.39. Hence two layers would be R = 2 x 0.39 = 0.78 = you're forked if your R requirement is +2! The first thing * I would do* is to do is check with either the manual and/or manufacturer and confirm the R value requirement.

My Englander 30-NCH required a hearth R value of 1.5. I used 4 layers of Durock Next Gen to meet that requirement (1.56).

Some pics of my hearth:

IMG_20141003_150453191_HDRLarge_zpsf83f481a.jpg
IMG_20141008_085657747Large_zpsc120ceb0.jpg
IMG_20141111_091615408_HDRLarge_zps6a72bc83.jpg
 
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That's a damn nice job FTG-05! Looks great!
 
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Chris H, what stove is this for?
 
begreen said:
Chris H, what stove is this for?
Click to expand...
I am going to get a us stove pedestal king 2007b. Like I said earlier, kinda confused about the conversion of the K factor to r value! Lowes here has a hearth board that I can join together with a kit. The hearth board has an r value of 1.5. So if I use the hearth board..2 layers of next gen durock that has an r value of 0.39 ( thanks FTG-05 for that info!...your hearth is awesome looking!)...I can get an r value of 2.28....
 
Here is an article that explains k vs r.
https://www.hearth.com/econtent/index.php/articles/k_values_what_does_it_all_mean

If you can find micore that would be great. I was,able to find some old office partitions for a few bucks and strip the micore out of it. It has no structural integrity though, almost like compressed newspaper. You may also consider using 2x2 inner framing so that as you build it up it will come level or just above the surrounding 2x4's. That way you don't end up with an 8" high hearth. I also tend to over build so personally I wouldn't consider the air space in my calculations. I would build it up to the recommended r value and consider the air space as added protection.
 
Why do you need any framing under the Durock at all? Start layering Durock from the existing floor up and you'll have more than enough R value by the time you are flush with the 2x4 surrounding frame. Assuming R of 0.39 per half inch of Durock, 3 inches (6 layers) gives you R of 2.34.
 
jkranes said:
Why do you need any framing under the Durock at all? Start layering Durock from the existing floor up and you'll have more than enough R value by the time you are flush with the 2x4 surrounding frame. Assuming R of 0.39 per half inch of Durock, 3 inches (6 layers) gives you R of 2.34.
Click to expand...
Depends on what type of finish he wants to put on the front and sides, I guess.
 
A hearth pad can be flush with the surrounding floor, right? If the pad is raised by studs simply around the periphery, not under the center, and if the periphery is at least the width of the studs wider than is called for by code, then the studs under the pad at the edges are more fire resistant than the bare wood floor would be at the same distance. And bare wood is code there.
 
whit said:
A hearth pad can be flush with the surrounding floor, right? If the pad is raised by studs simply around the periphery, not under the center, and if the periphery is at least the width of the studs wider than is called for by code, then the studs under the pad at the edges are more fire resistant than the bare wood floor would be at the same distance. And bare wood is code there.
Click to expand...
yes a hearth pad can be flush but not sure what you are asking and also not sure what you could use to span that far without support. It is much easier to just frame it to the height you want and add multiple sheets of backer to add up to the correct r value
 
https://www.hearth.com/econtent/index.php/articles/hearth_design

Use this to help you. I used 18 gauge metal studs to create an airspace between the hardwood floor and the durock that would be noncombustible and increase R value. I didn't want a bunch of layers of durock and raise it too high off the floor. I only needed two layers. It all depends on the design you are going for. You can get them at your drywall supply store. They cost me $100, but I was also able to create a 1 inch airspace behind my stove to gain closer clearances to the combustible wall behind. You can also check out my thread titled Hearth Install.


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