Low Profile Hearthpads

[holysmokers]

Ok folks, I got the stove ordered after two years of research. (Hearthstone Homestead in blue-black satin) Now I need to construct my hearthpad. I just picked up two 4 X 8 sheets of micore 300 at 1/2" thick. The scenerio is 1" high plush carpet with pad over 3/4" plywood subfloor. I have already realized that the only way I can achieve the required R-value is to rip up the subfloor.
I would like to keep the pad the same height as the carpet for asectic purpose but I don't know if I will be able to do that with such a high R-value. According to the manual this stove requires R 2.5. If I double up the micore, that will give me 2.2. Then add two 1/4 inch sheets of cement board one above and one below that brings me to 2.4 r-value and 1 & 1/2" in height. I was wondering if I could substitute some air space instead of another sheet of micore. How would I do that? With shims over the joists as spacers ?
Then to finish, a layer of porcelin tile or granite tile. Another question: I can only seem to come close to the required r-value but not complete it, anyone have any ideas or experience here?
Another question, what kind of cement board is best for this application. The manual lists durock and wonderboard, will hardibacker work ? Are all three listed as "Non-Combustible" with the NFPA ?
What tool would I use to cut the subfloor in the corners perpindicular to the wall where the circular saw won't reach?
Thanks, Holysmokers

 

[Todd]

Not sure on this but doesn't the Homestead have a bottom heat shield to reduce those R-values?

According to my old Homestead manual it states 1/8" airspace equalls .92 r-value. I can't find anything about bottom heat shield clearance.

 

[holysmokers]

Yeah, the Homestead does have a heatshield included, however I don't think it changes the r-value any. I might try to call Hearthstone they will know for sure.

 

[Harley]

Because of the slow connection here, I didn't look at the manual online, but I just am in the middle of an install of a Hearthstone Heritage, which only calls for hearth pad R- value of 1.2... Is there really that much of a difference between the stoves? That, to me, seems like a lot. - especially with the heat shield.

Unfortunately, because I'm an idiot, I deleted the early pictures of the hearth construction here... that's only being done because I wanted to raise it up, since I was going from a top loading, to a front loading stove.

I think the micore and other type of well insuluting material is a pretty soft material to work with, so, not being a construction type of guy, could you do something like DonCT's hearth with metal framing, only lower?

 

[elkimmeg]

I read your manual concerning floor protection. It confirms the R-2.5 with a stove having 6" legs and bottom heat shield. The stove with 4" leg options and no heat shield is R6.6

Couple of point about some of your purposed installations
Do not remove the main sub floor to the joist.. That plywood is sized to carry the floor load and weight. Cement board 1/4 or 1/2"
is not rated in the mid spands 16" on centering of joist, to carry and properly distribute the weight. The orriginal sub floor decking has to stay. The rug and pad should be removed and if there is a layer above the main sub flooring, that too can be removed.
The instruction manual has done a very good job of explaining the required process of custom built pad ,including listing the r value properties of common materials,, for its construction. I would not use 1/4" cement board on the top layer it is not ridgid enough to be shifting the placement of a 400 lb stove, You run the risk of cracking it or breaking it even with it tiled. The .2R value of cement board is for 1/2" thickness. As for trying to make it flush with the rug, probably not going to happen. unless your rug has 2" pile.

Even with a bottom layer cement board two layers of micore and top layer cement board total R-2.6, tile in top, the finish product will be 2.25" thick from your sub floor. IF being flush is you biggest concern, You have one other option. Return the stove and buy another model or another manufacturer's stove,that has the listed requirements for floor protection that will work.

Another note, floor protection is a tested process,, proven and becomes part of the stove installation and listing. This is the minium exceptable r-value. There is no penalty of exceeding the minium R-value.

 

[holysmokers]

Wow, Thanks Elkimmeg!! You just saved me some major headaches. I wondered about the weight distribution on the cement board. Fortunatly, I just ordered the stove a couple days ago and I can cancel. I talked to two tile contractors last week and one of them suggested to leave the subfloor. The second one suggested to remove it!! He was the one that charged me $50. for a "consultation" and then gave me lousy advice. Man am I glad I found this forum Now I'm going to make some phone calls.

 

[webbie]

IF being flush is you biggest concern, You have one other option. Return the stove and buy another model or another manufacturer's stove,that has the listed requirements for floor protection that will work.

There is possibly the option of cutting the floor joist down in order to recess and new subfloor in that area, but only with proper guidance on the spans of the joist below it.

I think even a slightly raised hearth can look fairly flush, so you might be OK with the one or two inches above the carpet. Only problem is if it is in a high traffic area and you want to be able to walk over the hearth edge without tripping.

 

[elkimmeg]

Want to save big money? Screw the tile guy Do it yourself. If you made the pad larger you could wood finish it with moldinghs
Remember once you exceed the distances from combustiables one can use them to finish off the edge Done right the wood molding can overhand the pad and cover up all outside tile cuts All one wouls have to do is find the center point and start applying tiles.
Screw the guy youpaid $50 for an estimate. I think that charging for such an estimate is bogus. If you need more advice just ask

 

[ScubaSteve]

I believe that if you are going by R value you can't add items together to get the required R value. Example micore 160 @ 1/2" = R value of 1.43 you can not add more layers to get 2.5. If you are going by K value then you can add to get you what you need.