hearth info.

[trailblaze]

hello, all... new to the forums, but been looking around and thought this would be a good place to say hi and ask a few questions...

first off, i bought a med. Dutchwest Cast Iron stove.....(wish i knew about the whole VC troubles before i put the order in) anyway, i am going to have someone put my chimmney pipe in up through the roof and all, but i am building my own hearth.

i was told to put a "space" between the wood floor and the surface where the stove will sit... is 1-2 inches enough?

secondly, can i use 2x4's as the spacing material and then lay plywood down, then cover that with 1/2" Hardiboard (cement board), followed by morter and 1.25-1.5 inch thick natural stone??

i figured with about 2 inchs of stone/cement board between the stove and plywood the heat would't cause any danger.... any thoughts?

thanks,

Matt

 

[begreen]

There's no need for the air gap and that amount of cement board. The stove calls for R .74. You can achieve that with just the cement board. I would lay down a sheet of plywood, then 3 layers of 1/2" durock or wonderboard cement board with tile on the top. If you want an extra margin of safety, put a layer of sheet metal between one of the layers of cement board. FYI - Hardibacker board has some cellulose in it and is not approved for this application. Durock and Wonderboard are, but be sure it is the pure cement board type and not their lightweight product.

 

[bcnu]

Don't forget our old friend Micore. One sheet of that and one of Durock would give plenty of R value.

 

[trailblaze]

wow.. ok i'll return the Hardibacker stuff... i only bought it because it says it's recognized as a non-combustable in accordance with ASTM E136..... it also to have a Thermal Resistance (Approximate value) 1/4'' thick @ R:0.13 so i would assume 1/2 thick is an R.26


sooo back to the drawing board... if i have chesapek river rock slabs/peices that are about 1-1.5 inches thick...does that mean i don't need any air space between the floor board if i put atleast 1 (1/2 thick) layer of durock as a base?? or perhaps 2 layers....

but if i wanted to raise the hearth up, i could use a 2x4 as support, lay 1/4-1/2 inch plywood down with the same (1 or 2) layers of durock and then my stone...


how much is the R value for stone?

 

[trailblaze]

well after reading the first page of this thread... i see hardibacker might be able to be used?

https://www.hearth.com/talk/threads/9045/

 

[trailblaze]

ok so nothing like filling my thread with my own posts but...

i just went out and measured my rock and it's atleast 1.75 inches thick....some 2inches soo with mortar i'd be 2" thick at a minimun


Anyone know what the R value is on a stone of that size?


also, from my stove manual...

Even when the bottom heat shield is installed, you
must provide special protection to the floor beneath.
For installation with the heat shield attached, use an
approved 5/8” (16mm) noncombustible hearth pad with
K = 0.84 BTU/in ft2 hr °F or an equivalent material with
an R-value of at least 0.744.

 

[begreen]

Hard to be exact, figure roughly R .08 for an inch of the stone. In other words, not much. If you raise the hearth with 2x4 sleepers, be sure to space them more closely, like 12" centers with 3/4" plywood or if 16" centers, put something rigid on top, like 5/4 plywood. You don't want this to flex at all.