How to "elevate" a 580 lb stove and/OR, what is the "R" value of "6 inches" of brick?

[tickbitty]

I know I have posted this already but it was as part of a longer thread on install, so I hoped if I broke this subject out I might get an answer.

I purchased a used woodstove, which is a "hearth stove" type insert in that about 10" or a third or so of the stove sits directly on the hearth.

Didn't realize until I nearly got it home that the stove is expected to be installed on a raised hearth of at least 6". My hearth is flush with the floor.

I need to figure out either what the R value of the 6" brick is, (the manual gives no such specs) and see whether I can somehow modify my flush hearth to comply, by replacing it with another material/subfloor or putting layers of something on top.

OR, I need to figure out a way to elevate the stove. (Actually Building a real raised hearth is not an option for me with this fireplace configuration.)

I think I could raise the stove itself and put it on stove board and that would be about similar to a freestanding stove, no? This is not the way I wanted it, but I want to make this work one way or another.

So, Can I put the stove on a pad of stacked concrete pavers or block which in turn sits on a piece of stove board? Or a stack of cement board? Or get a couple pcs of steel eye beams? Anything?

(Stove is an Englander 24 JC. Very nice stove. HUGE stove when it's not backed into the fireplace and is sitting in my dining room! Still waiting on liner quotes and now have this 6" issue.)

Thanks in advance for any insight or suggestions.

If you prefer, this is the other thread I had going about this stove and etc. https://www.hearth.com/econtent/index.php/forums/viewthread/45871/

 

[madison]

Too late now, my motto: Read 4x, measure at least twice, purchase/cut once.

Or craigslist it, who knows, you could recoop part of your $ on your mistake.

Last advice, don't compound your mistake, by risking you life with an inappropriate install, no matter how the "other guy" had it installed, just because he did it wrong does not justify the risks involved with ignoring the installation recommendations.

 

[pgmr]

If you raise the stove 6", will that still allow the back of the stove to slide into the fireplace? Is there only masonry underneath your existing hearth, i.e., is it part of the chimney structure or sitting on a slab foundation? If so, then you should have plenty of R-value underneath it. If not, you'll have to raise it, push it back into the fp farther so it is, replace the hearth or find a different stove.

 

[EatenByLimestone]

http://www.coloradoenergy.org/procorner/stuff/r-values.htm


This will tell you what 4" of brick will give you in R value.

Matt

 

[tickbitty]

Too late now, my motto: Read 4x, measure at least twice, purchase/cut once.

Or craigslist it, who knows, you could recoop part of your $ on your mistake.

Last advice, don't compound your mistake, by risking you life with an inappropriate install, no matter how the "other guy" had it installed, just because he did it wrong does not justify the risks involved with ignoring the installation recommendations.

It's OK, this is the kind of stove we were seeking regardless (a hearth stove) and I'll bet I would have had the same issue with other similar stoves, so we just need to find a way to make it work. It will be ugly, but safe and legal. The last guy had a raised hearth, and we don't. But we will raise the stove on masonry till it's the same difference. They didn't have a liner, but we will. (if I ever get any quotes I guess...)

I made 300$ profit on my last craigslist mistake stove (a Hearthstone II) so that didn't turn out so bad after all. This one we will use!

 

[tickbitty]

If you raise the stove 6", will that still allow the back of the stove to slide into the fireplace? Is there only masonry underneath your existing hearth, i.e., is it part of the chimney structure or sitting on a slab foundation? If so, then you should have plenty of R-value underneath it. If not, you'll have to raise it, push it back into the fp farther so it is, replace the hearth or find a different stove.

Yes the stove will still fit fine in the fireplace if it's 6" higher, and the clearances even work OK, just need a mantel shield for the bottom part of the mantel shield. And the chimney is masonry down to the ground, as is the inside of the fireplace. I am not sure but suspect that the (ceramic tile) hearth may have wood down underneath it and therefore not the necessary R value. However, if the stove is up 6" on masonry blocks on top of stove board, and the whole hearth is covered in stove board, that should make it similar to how it works if I had a stove on legs that was up on stove board.

I do plan to have this all checked out so I'm not going to do anything reckless.

 

[tickbitty]

http://www.coloradoenergy.org/procorner/stuff/r-values.htm


This will tell you what 4" of brick will give you in R value.

Matt

Thanks Matt! I saw a similar chart, but the charts I looked at give a figure for 4" and 8", but not for 6". And since the value for 4 is not half what the value for 8 is, it doesn't seem as simple as averaging the two - or would it be? It does appear though that concrete block has double the R value that brick has. So 6" of concrete block base raising the stove might have double the R value of brick, and would be the required 6" then as well so it seems like that might be OK.

 

[Beetle-Kill]

I honestly don't know if this will be relevant for your situation, but here goes. My existing hearth is only tile and plywood underlayment, no wonderboard or the like. Yep', it's gotta go, but winter is here, so it stays until spring. So what to do? I stuck a 500lb.+ Timberline on it, on top of a steel hearth "riser", and the ice melts faster in my glass than on the tile. I built a total of 6" rise, using 3/16" plate for the surface area. This extends 3" on all sides from the exterior sides of the stove. The support legs are welded to the top plate , centered at the contact points of the stove legs. The legs are 5x5 square tube, with base plates measuring 6x6", 3/16" thick. Using the big tube, and bigger bases helped spread the weight of the stove over a larger area. I also use an oscillating fan to spread the heat, about 22' away, and even when it's crankin', the tiles don't get more than warm. I am positive the free air space is more than adequate. This is a tight clearance, corner install, with heat shields on the sides. I hope this helps. BTW, It only took me 1.5 hrs. to build the whole thing, so don't let a "fab" shop tell you it'll take more than 2 hrs., + material costs. Really very simple.

 

[begreen]

tb, were you able to contact Mike? What did Englander support say?

 

[tickbitty]

tb, were you able to contact Mike? What did Englander support say?

Nothing yet. I think he is just really busy. (magnaflex too!) I'll be patient, that stove isn't going anywhere for a while.

 

[tickbitty]

I honestly don't know if this will be relevant for your situation, but here goes. My existing hearth is only tile and plywood underlayment, no wonderboard or the like. Yep', it's gotta go, but winter is here, so it stays until spring. So what to do? I stuck a 500lb.+ Timberline on it, on top of a steel hearth "riser", and the ice melts faster in my glass than on the tile. I built a total of 6" rise, using 3/16" plate for the surface area. This extends 3" on all sides from the exterior sides of the stove. The support legs are welded to the top plate , centered at the contact points of the stove legs. The legs are 5x5 square tube, with base plates measuring 6x6", 3/16" thick. Using the big tube, and bigger bases helped spread the weight of the stove over a larger area. I also use an oscillating fan to spread the heat, about 22' away, and even when it's crankin', the tiles don't get more than warm. I am positive the free air space is more than adequate. This is a tight clearance, corner install, with heat shields on the sides. I hope this helps. BTW, It only took me 1.5 hrs. to build the whole thing, so don't let a "fab" shop tell you it'll take more than 2 hrs., + material costs. Really very simple.

Huh, cool - got pics? Sounds interesting (and perfectly safe). Did you use an insert in the open then and that's why you had to build legs?

 

[begreen]

I could be wrong, but given the tiny notice in the Englander manual, it looks like they want a 6" air space to reduce the radiant heat level on the lower part of the hearth. The R value of an open horizontal air space is low due to convection. They would have to explain why, but I suspect it may be to increase the radiant angle to the simple, non-combustible hearth, 6" below.

If this is correct, but you want increased peace of mind and to be set up for a future insert, the hearth install might be more straightforward. Here's my thinking:

If the stone slab is the desired as a hearth, I'd place it on a sheet of micore, with a sheet of durock or cement board screwed down from the top. The micore might be overkill, but it will increase peace of mind and future options. Micore has an R value of 1.03 for 1/2" thickness; cement board = .254 for 1/2", the stone slab's R value depends on the stone, but let's say it's limestone at .153 per inc. If the stone is 3" thick, then the total protection will be 1.743 which is significantly more than a 6" open air space. Want a higher R value? Increase the micore layer to 1".

An alternative would be to build up the height of the hearth support for the stone slab so that it traps an air space. Air is an effective insulator in a trapped air space, figure roughly R = 1/ inch. Creating a support out of hat channel with a slab of cement board on top might work for that approach.

FYI - 2 1/4 brick has an R-value of .45, 4" = .8

more info at:
https://www.hearth.com/econtent/index.php/wiki/Hearth_Design

 

[tickbitty]

Very interesting and this is the kind of thing I was hoping to hear - exactly what that 14" minimum hearth that is 6" high is supposed to do and how I can do it. Husband doesn't want to use the stone hearth at this point, because it weighs like 600 lbs and so does the stove and he's a bit afraid of that big concentration of weight in one spot in the house... plus we would then need to raise the mantel or cut the bottom of it off to get the stone in. We just have a crawl space under there so I am going under this week to find out exactly what's under that hearth and also see what the distance is in the crawl - we may be able to eventually put a cement slab through the hearth area I guess.

But I do appreciate the information very much and the ideas regarding the micore and cement board for increasing some of our options.

Still thinking that I can just put down a stove board with a cmu base to 6" and get the elevation and a safe R value all around. It will be ugly though. I may talk to husband about whether he wants to make it work or get a more flush insert or something, but I am inclined to think we will give it a try. I'll be sure to post my ugly pics if we ever get it going!

 

[pgmr]

Can't tell from pictures, but does this stove have a double bottom - a space for air to be drawn or blown in and circulated around and vented out the top? If it does, you might try a test burn outside and measure the temperature of the bottom plate after several hours of high burning without the blower running. If you can get it up on some concrete blocks you'd have enough room to use a IR thermometer to get some readings. The hottest parts would probably be the edges where heat can be conducted down through the steel. A 5' piece of hvac ducting makes a good temporary flu.

If you ran the stove for 4-6 hours and didn't find any temps over 150F on the bottom plate, you'd probably be ok to use it without rebuilding the hearth, but you could also raise it up slightly with some blocks of concrete board an inch or so high to allow airflow under the bottom.