New guy hearth pad questions

[Smith]

Greetings,
So recently I've decided to put a wood stove in my basement. We're planning on getting the Englander 1800 from Home Depot. The manual says to have a pad under the stove that is 2 inches thick and has an R-value of 2. Any thoughts on how to do a simple pad would be great. I've read about using metal studs and wonderboard and insulation. Is that strong enough to hold the stove?

 

[begreen]

Howdy, would this be the Englander 13NC? This stove has a very high insulation requirement. If so, there are some example threads that detail how this is done. Done correctly the hearth will definitely support the weight of the stove, especially if the cement board is doubled up (1" thick). For extra peace of mind you could pop rivet a skin of 22 ga sheet metal on top of the metal studs. Or lay down a layer of cement board, then the micore insulation followed by a double layer of cement board. You can also use hat channel laid flat at 12" spacing for a nice solid base.

Is the basement floor cement or made from a combustible (like wood)?

 

[Danno77]

following. If this is in your basement it might be easier to get rid of whatever flammable flooring you might have and tile in that spot. Then you'd be good to go. Nothing wrong with a hearth, though, and you could avoid losing heat through an uninsulated floor.

 

[Highbeam]

This will not be easy for you. An R value of 2 is tough to attain without the use of the micore insulation board and that micore can be very very difficult to source. It is unfortunate that Englander could not design their stove to prevent this requirement.

 

[Danno77]

it's easy enough, just start layering up durock and call it a day. A nice hearth that keeps you from bending way over isn't necessarily a bad thing, either. In my mancave I have 5 sheets with tile on top. I think that gets me to 2, or at least close enough that I'm not losing sleep over it.

 

[PapaDave]

Wonderboard 1/2" is .26 R. Do the math.

 

[Danno77]

Durock is .39 for 1/2"

 

[begreen]

Pure cement board is R=.26, but that's almost all gone by now. If it is Durock NexGen or Wonderboard NexGen then the rating is now R=.39.

 

[begreen]

Crap, I see that Wonderboard has changed their website and spec sheets again. This is getting to be an annual occurrence. Not sure if they dropped the Next Gen product or not? Does anyone know? Our local yard only sells Durock.

 

[Danno77]

seriously? That is getting old. I feel like hours of my life have been wasted on the internet trying to sort through spec garbage from these backer board companies data sheets. I don't plan on doing anything hearth related soon, though, so I can probably relax.

 

[begreen]

It's nuts. Used to be just one (or two if you include hardibacker) specs for years. Then about 3 yrs ago they started introducing NexGen products. The hearth world was abuzz because the rumor was that these products had styrofoam mixed in. That was proven wrong or a case of mistaken identity. They use pumice or perlite as a lightner/filler. The styrofoam filler product is Fiberock IIRC and should not be used for a hearth.

 

[PapaDave]

Hmm, when I checked, the info I got was .26.
If it's been upgraded recently, cool beans. Rebuilt my hearth in '10.
If I got the gooder stuff, I'm right there.
Thanks begreen.

 

[begreen]

It's always fine to exceed minimum specs.

 

[Highbeam]

When I bought the 1/2" durock it was 60lbs per 3x5 sheet. Each layer of this stuff requires about 100 lbs. 6 layers later plus tile, thinset, and screws and you are up into the 700 lb range. Then add a 400lb stove, 50 lbs of firewood, a couple of fat guys warming their buns, a kettle full of water, and an easy 1600 lbs is being rested on your floor joists. Cripes!

Yes, a zillion layerd of durock will get you there.

 

[Danno77]

but it's in his basement...

 

[Highbeam]

but it's in his basement...

So you are assuming a slab on earth? Then R value of the hearth does not matter unless you build e raised hearth out of comustible materials.

 

[Danno77]

I'm interested to hear what he says his floor is, but I'm either picturing vinyl flooring or some carpet or something. And maybe he wants a hearth that could be taken up some day if he just builds right on top of that. Either way, I'm with you that it doesn't matter unless you build a raised hearth, but even then the framing of the hearth would be resting right on the slab, so it could easily handle thousands of pounds.

We are an impatient bunch filling in the gaps without the original poster. Wonder when he'll be back to comment on it.

 

[Highbeam]

The slab, if done properly, could easily support the weight of a stack of durock plus stove. The carpet or other flooring that is trying to be preserved might not survive the compression without permanent damage.

It's fun to fill in the gaps.

 

[Smith]

Sorry it took me so long to get back on . My computer blew up this weekend. My floor is carpet then plywood then 2x4s on pea gravel. So I can't really get rid of the combustibles. I was planning on removing the carpet but I can't get rid of the plywood.

 

[Danno77]

i've never heard of such a thing. the floor isn't even 2x6 or heavier? how well do they prep it before they put the gravel on there? if it's pretty firm, then weight shouldn't be an issue and you can use durock or some equivalent. I highly suggest that you remove the carpet like you planned on, though.

 

[Highbeam]

2x4 sleepers on pea gravel? Oh my god! Most wood sheds on this site have a better floor system than that. Pea gravel does not compact so you know the sleepers have sunken into the gravel and that the plywood is directly on the rocks. The point though is that your floor is combustible so you need to honor the R-value requirements for the hearth. I have no qualms about building all of this on top of your carpet but be warned that your carpet will be smashed flat and may not ever look the same should you remove the stove someday.