# Advice on designing hearth flush to floor



## Moorboy3 (Mar 28, 2014)

I was wondering if anyone can advise me on constructing a hearth that will be flush - or as near as possible - to our hardwood floor. I'm new to wood stoves, and my contractor and architect also have only limited experience in this area.

I've found this site invaluable! Thank you so much.

After many weeks of trawling the building code and multiple redesigns we finally have installed flue and stove pipe for a Jotul F3. Our engineer has said that we can remove the floor and subfloor as the floor joists have been reinforced. We will bridge the spaces between the joists with plywood so this will be flush with the top of the joists.

That leaves 1.5" to the surface of the hardwood floor. Within this thickness we need to get an R>1 and some kind of stone (slate? Basalt?) on top. I don't know how thick the stone has to be so it doesn't crack under the stove legs.

We were thinking of using this Hy-C stove board to give the R value as one layer. Does that sound suitable? Can stone or tile go directly on it or is it too soft?

Any thoughts or links/references gratefully received.

Here's a rough sketch...


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## begreen (Mar 28, 2014)

You should be able to do this with a 1/2" layer of Micore (300 or SB), 1/2" cement board, latex modified thinset and then a 3/8" stone or tile top.


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## begreen (Mar 28, 2014)

If you want premade, Yoder Hearth Classics are 1 1/4" thick. 
http://www.hearthclassics.com/yoder_original_sizes.php


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## GENECOP (Mar 28, 2014)

Ok First off if you are committed to a flush condition the basic plan is fine with the exception of the single 3/4" between the joists.....double that up....either use 2x material or double 3/4" which would be better...glue and screw the whole system together stability will be key to your top stone not cracking....over the whole system install 1/4" hardy board...this will leave you 1-1/4" to FF.....now you will need a 1" stone....+ 1/4" thinset...That would work.....however being a decorative concrete guy I would Pour directly over the hardy ...1-1/4" of solid concrete with diamond lath embedded....you need someone who can finish concrete well...you can add color to match any stone you want...you can embed or stamp...your options are endless...let me know if you need more specifics...or options...


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## begreen (Mar 28, 2014)

If they need an R=1.1 rated hearth, 1/4" of Hardibacker is not going to accomplish that.


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## M1sterM (Mar 28, 2014)

I'll let others chime in on the insulation board.

I'd second the doubling up the plywood that's fitting between joists.

Also, if you have access from below, maybe use plywood on the bottom of the joists, as well, as I'm not too confident that recessed ply between the joists would tie the joists together as positively as if it was a continuous sheet over the top.  Putting ply on the bottom would help create a giant box beam that would really ensure no flexing (which will not do good things for tile or stone).  At a minimum, bridge the joists in a couple locations under the hearth (with smaller material than the joists, to allow the recessed ply).


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## GENECOP (Mar 28, 2014)

begreen said:


> If they need an R=1.1 rated hearth, 1/4" of Hardibacker is not going to accomplish that.



Maybe not but 1-1/2" of cementious material under a stove will never be a problem...I don't care what might drop out the front door.....of the stove...


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## begreen (Mar 28, 2014)

The issue is not embers, it's heat transfer. Cement mortar has an R value of 0.2/inch.


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## GENECOP (Mar 28, 2014)

M1sterM said:


> I'll let others chime in on the insulation board.
> 
> I'd second the doubling up the plywood that's fitting between joists.
> 
> Also, if you have access from below, maybe use plywood on the bottom of the joists, as well, as I'm not too confident that recessed ply between the joists would tie the joists together as positively as if it was a continuous sheet over the top.  Putting ply on the bottom would help create a giant box beam that would really ensure no flexing (which will not do good things for tile or stone).  At a minimum, bridge the joists in a couple locations under the hearth (with smaller material than the joists, to allow the recessed ply).



If you look at his drawing he has kleets running along the length of the joists ....the plywood should be glued and screwed to that...essentially that will form a solid box....


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## GENECOP (Mar 28, 2014)

begreen said:


> The issue is not embers, it's heat transfer. Cement mortar has an R value of .2/inch.



I would be even less concerned with a new stove.......how hot would the BOTTOM of the stove have to get to ignite Doug fir 1-1/2" below concrete?   I don't think the bottom of the stove would be remotely close for ignition to occur....


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## begreen (Mar 28, 2014)

It has nothing to do with whether the stove is new or not. Every stove varies. Some only require ember protection, some require exceptional protection. The hearth must meet the manufacturer's minimum spec.


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## GENECOP (Mar 28, 2014)

begreen said:


> It has nothing to do with whether the stove is new or not. Every stove varies. Some only require ember protection, some require exceptional protection. The hearth must meet the manufacturer's minimum spec.


 
I don't entirely disagree with meeting the manufacturers specs.....I will say,  and I am sure the By The Book guys will have a field day...that some of the specs are so mired in liability concerns that they are way over board in what they suggest.....certain times when building, the client requests a detail....sometimes to satisfy,  margins must be pushed...not ever pushed to there limits,,, I would never suggest that....just pushed a little beyond the specs....Commercial airlines built by Boeing are designed to not exceed 40,000 ft....they can fly much higher....most things have built in margins...this guy is looking to pull something off in 1-1/2"....I believe it can safely be done...even if the I's are not dotted and the T's not crossed....just my opinion after years of building things....no disrespect intended...


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## begreen (Mar 28, 2014)

In the field you may be right, sometimes and sometimes not. Some stoves get the hearth very  hot. Heating with a hot fire, in a home should have a generous margin of safety. It has to satisfy the insurer and inspecting authority which will be guided by the manufacturer's tested specs.

FWIW, my wife's childhood home nearly burned down due to heat transfer through a 6" stone and mortar hearth to the wood supporting it. It took 40 year for it to happen, but pyrolysis eventually lowered the ignition point to the point where timbers caught fire. Fortunately for all it was caught and put out early.


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## GENECOP (Mar 28, 2014)

Maybe something like this sandwiched between the Hardy and Slab


http://www.csiaccessories.com/25070.html


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## bholler (Mar 28, 2014)

I am totally with begreen on this one go with the specs of the stove at a minimum.  If it requires insulation there is a very good reason and you really don't want to push your luck.  If you don't know what stove you will be using yet either figure it out before you start or build to the most stringent requirements you can find that might be the way to go anyway so if you decide to change stoves later you will have no problems.   And i have to say that when you are dealing with a fire in a metal box in the middle of a house you really should be a "by the book guy".


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## elmoleaf (Mar 28, 2014)

I'm confused. An architect is a licensed professional who should be able to research the codes and design this for you. What services are they providing? Or is this person a designer without a professional stamp?


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## GENECOP (Mar 28, 2014)

I always enjoy figuring this stuff out.....if you want to go by the book forget the Hardie....Go with Astro foil, it exceeds the R value needed....5/6" thick, pour over.....here is the link

http://www.videcomp.com/reflectech/astrofoil.html#Features


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## GENECOP (Mar 28, 2014)

The minimal compression of the Astro should be consistent and minimal, the concrete would hold IMO


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## bholler (Mar 28, 2014)

I am sorry genecop I don't see how could work it is not rigid and not classified as non combustible it is just class a fire rated.  Something like  Micore needs to be used


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## begreen (Mar 28, 2014)

plastic air pockets doesn't sound like a base for anything hearth related.


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## bholler (Mar 28, 2014)

begreen said:


> plastic air pockets doesn't sound like a base for anything hearth related.


agreed


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## Highbeam (Mar 29, 2014)

Only a fool would build or recommend building something not by the book when the results can so easily be deadly. None of us know how much extra margin for safety any of the minimum specifications has as extra. I cheat on plenty of stuff, but only where the results of failure wont kill anybody.


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## elmoleaf (Mar 29, 2014)

Well, here go my 2 cents:
1. Strip floor and subfloor to floor joists as proposed.
2. Add perpendicular solid blocking between joists at 12" on center (ideally, locate blocking at stove leg locations).
3. Add 1/8" continuous plate steel over top of floor framing, drill and screw 16" or 12" on center each direction.
4. Adhere 1/2" layer of micore 160 (for r value)
5. Adhere 1/2" layer of cement board.
6. Thinset and finish with 3/8" tile. There are many color/finish options for tile, some look like stone...there is even tile now that looks like wood.
This should put you close to flush or slightly proud of existing floor. Hold back tile and cement board at perimeter to allow installation of beveled wood transition trim.

If you want to omit the steel in favor of your recessed 3/4" plywood, still add perpendicular solid blocking, but you can hold it 3/4" below tops of existing floor framing.  Make sure your 2x cleats are screwed and glued to the existing joists. Keep in mind top of existing floor framing is not likely to be perfectly level across the tops of all the members.

Good luck.


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## bholler (Mar 29, 2014)

I agree with everything but the steel plate I don't see any reason for it.


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## begreen (Mar 29, 2014)

Yes, the steel is not needed and makes it a lot harder to screw through. I prefer micore 300 for greater density. But I don't agree with the adhering, it's unnecessary. Screw down the sandwich of Durock and micore every 8" as recommended and it is  totally captive and going nowhere. The adhesive is dubious for hearth use and adds nothing.


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## skinanbones (Mar 29, 2014)

I'm not sure what the r value on granite is as here in canada we only need ember protection.  We had a client go to a supplier of granite counter tops and picked out a 3/4 slab and had that cut to the size required for his jotul castine.  That granite was the same thickness of the hardwood flooring that was used and when finished look amazing.


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## begreen (Mar 29, 2014)

In Canada I would think that the stove would need at least meet the mfg. tested standard.  I have never read about Canada having more lax hearth standards. Nor have I seen ember protection only required if installing in Canada in any manual.  If anything hearth reqs.  are a bit more strict, requiring 18" in front of the door.


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## elmoleaf (Mar 30, 2014)

bholler said:


> I agree with everything but the steel plate I don't see any reason for it.


As I described it, he wouldn't have the 3/4" plywood he described. Thus the steel is required for structural support of hearth and stove....to eliminate flexing of micore and cement board, especially if his stove legs don't align with the floor joists. Tile and 1" of micore/cement board alone have insufficent structural strength for span between floor joists if load is applied.
Construction adhesive, in modest amounts at the perimeter areas, will help the sandwich of materials to act as a monolithic element (similar to reason why when you build a built up beam from 2x material, you don't just locate them parallel...they get fastened together). And as noted, micore and cement board really can't be screwed down to a steel plate.
I don't  think the micore 300 gives sufficient R value?
However, as described at end of my first post, he could eliminate supporting steel by using his original cleat/recessed 3/4" plywood system but with added solid perpendicular blocking. I agree the all wood solution is seemingly "easier" given that materials are readily available. It just requires a lot more fussing with cleats and getting them all dead level so the inset plywood is dead level with tops of joists, some of which may crown up or down. One sheet of steel over joist tops can eliminate most of that time and effort.

It'd be interesting to know how the OP proceeds and see some pictures.


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## bholler (Mar 30, 2014)

yes but he was going to put ply between the joists on top of cleats so I still se no need for the steel.  That steel will cost a whole lot more and ad a un needed complexity to it.


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## begreen (Mar 30, 2014)

They require an R=1.1 hearth for the F3CB. 1/2" of Micore 300 = 1.03 + 1/2" Durock NexGen (@ .39) total R = 1.42


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## bholler (Mar 30, 2014)

I would just like to point out one thing that I have been told I don't know how much of a concern it is but I have been told not to use screws in this situation and instead just use thinset between the layers because of heat transfer through the screws.   I honestly don't know if it is really an issue but I know I remember someone telling me that and it does make some sense.


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## begreen (Mar 30, 2014)

I think that is a non issue. The durock should be screwed down.  Thinset won't bond well to micore, it's a fibrous material.


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## bholler (Mar 30, 2014)

Ok I just though id throw that out there.  I think the easiest option here would be to simply buy a manufactured stove board and sit it in the recess.  I think that is what I would do.  I am sure it would cost a little more but not if you are paying to have the work done.


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## Grisu (Mar 30, 2014)

bholler said:


> I would just like to point out one thing that I have been told I don't know how much of a concern it is but I have been told not to use screws in this situation and instead just use thinset between the layers because of heat transfer through the screws.   I honestly don't know if it is really an issue but I know I remember someone telling me that and it does make some sense.



If the screws are just used to connect non-combustible materials like Micore and Durock I don't see how any heat transfer could be worrisome. It may be different if they end up in a wood support. To avoid that I would screw the first layer to the wood support and then use screws at an offset to attach additional layers. That should avoid any thermal bridging.


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## jkranes (Mar 30, 2014)

As I have heard it, thinset is always used between sandwich layers.  The purpose is not to act as adhesive but to fill in any potential air gaps.  Otherwise the upper layer can flex down into the gap and crack the tile job.


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## fire_man (Mar 30, 2014)

I'm not sure it's a good idea to put thinset on the micore, the moisture might not be a good. Also, that stuff is like styrofoam and I don't see how it would adhere in the least.


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## fire_man (Mar 30, 2014)

bholler said:


> I would just like to point out one thing that I have been told I don't know how much of a concern it is but I have been told not to use screws in this situation and instead just use thinset between the layers because of heat transfer through the screws.   I honestly don't know if it is really an issue but I know I remember someone telling me that and it does make some sense.




I have a sheet of micore waiting to install. No way would I trust thinset to captivate that stuff. It easily crumbles and I cannot see how the thinset would adhere. Maybe some kind of adhesive would stick, but I would not use adhesive in a hearth.


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## geo91324 (Mar 30, 2014)

I had exactly the same situation as the OP when I switched out my Encore (which sat mostly inside my kitchen fireplace) with my Heritage (which sits completely outside the fireplace). The small existing stone hearth was removed and I built a slate hearth deeper into the room, butting up to the hardwood. I wanted an R value of over 1.0 (if you've ever stuck your hand under (not in front of, under) a stove with a raging fire going you know the flooring can get hot. Stone, cement, granite, etc. have virtually no R value, so that heat would be transferred directly to the subfloor.
I did exactly as the OP suggested by cutting the subfloor plywood flush with the joists and blocked them appropriately underneath. Then, as Begreen suggested, I used micore and durock with, in our case, the slate on top of that. Of course, it's still a good half inch or so taller than the wood floor. (A project for this spring: bevel the edges.)


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## skinanbones (Mar 30, 2014)

begreen said:


> In Canada I would think that the stove would need at least meet the mfg. tested standard.  I have never read about Canada having more lax hearth standards. Nor have I seen ember protection only required if installing in Canada in any manual.  If anything hearth reqs.  are a bit more strict, requiring 18" in front of the door.


 

Begreen yes it is true that our dimension are larger 18"  in front of the door and 8" on the other 3 sides, but our only requirement is ember protection.  There is no mention of building hearths with an r factor for a certified stove. 
This is why certian jotul stoves have bottem heat shields installed from the factory and why all vermount castings stove required a bottem heatsheild when installed in canada.


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## Moorboy3 (Mar 30, 2014)

elmoleaf said:


> I'm confused. An architect is a licensed professional who should be able to research the codes and design this for you. What services are they providing? Or is this person a designer without a professional stamp?



The architect and contractor are both excellent but none of us have had much experience in this area. We didn't want to reinvent a complicate, code compliant solution if people in the wood burning community had experience of this problem they would be willing to share. And share they have - thank you all so much!

Reading through the great responses posted it looks like our proposed solution - with a few mods - should work.


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## Moorboy3 (Mar 30, 2014)

elmoleaf said:


> As I described it, he wouldn't have the 3/4" plywood he described. Thus the steel is required for structural support of hearth and stove....to eliminate flexing of micore and cement board, especially if his stove legs don't align with the floor joists. Tile and 1" of micore/cement board alone have insufficent structural strength for span between floor joists if load is applied.
> Construction adhesive, in modest amounts at the perimeter areas, will help the sandwich of materials to act as a monolithic element (similar to reason why when you build a built up beam from 2x material, you don't just locate them parallel...they get fastened together). And as noted, micore and cement board really can't be screwed down to a steel plate.
> I don't  think the micore 300 gives sufficient R value?
> However, as described at end of my first post, he could eliminate supporting steel by using his original cleat/recessed 3/4" plywood system but with added solid perpendicular blocking. I agree the all wood solution is seemingly "easier" given that materials are readily available. It just requires a lot more fussing with cleats and getting them all dead level so the inset plywood is dead level with tops of joists, some of which may crown up or down. One sheet of steel over joist tops can eliminate most of that time and effort.
> ...



This is great. We hadn't thought of sheet steel as an option but I'll look into this. Unfortunately the location of the stove is directly above a load of water pipes coming from the basement so access to the space is pretty much only from above by cutting thru the floor. It may be time saving to use a slab of steel. 

Also, you're right about the micore 300. From my reading only the 160 has enough R value at the thicknesses we were looking for. 

I'll post pics once we start the work!


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## Moorboy3 (Mar 30, 2014)

begreen said:


> They require an R=1.1 hearth for the F3CB. 1/2" of Micore 300 = 1.03 + 1/2" Durock NexGen (@ .39) total R = 1.42



That leaves me with 1/2" to play with for thinset and some kind of tile or stone. This might just work!
Thanks for your input.


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## Moorboy3 (Mar 30, 2014)

Grisu said:


> If the screws are just used to connect non-combustible materials like Micore and Durock I don't see how any heat transfer could be worrisome. It may be different if they end up in a wood support. To avoid that I would screw the first layer to the wood support and then use screws at an offset to attach additional layers. That should avoid any thermal bridging.



I had not thought of this issue, but ill look into this further as I'm basically paranoid. 

Am I not right in saying that when using a rear heat shield with air gap you would ceramic spacers but steel screws? This seems like a similar situation but on below the stove. I think you are not supposed to use screws directly behind the stove. I wonder if this is why.


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## begreen (Mar 30, 2014)

skinanbones said:


> Begreen yes it is true that our dimension are larger 18"  in front of the door and 8" on the other 3 sides, but our only requirement is ember protection.  There is no mention of building hearths with an r factor for a certified stove.
> This is why certian jotul stoves have bottem heat shields installed from the factory and why all vermount castings stove required a bottem heatsheild when installed in canada.


What happens when an Englander 13 NC or a Hearthstone Homestead is installed in Canada?


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## skinanbones (Mar 31, 2014)

not sure as neither company have much of a canadian presence.  The few hearthstone we ran across all had bottem heatsheilds, i never seen an englander here in ontario


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## M1sterM (Mar 31, 2014)

GENECOP said:


> If you look at his drawing he has kleets running along the length of the joists ....the plywood should be glued and screwed to that...essentially that will form a solid box....


Cleats don't form a box, unless they are bridged along the bottom, too.


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## begreen (Mar 31, 2014)

skinanbones said:


> not sure as neither company have much of a canadian presence.  The few hearthstone we ran across all had bottem heatsheilds, i never seen an englander here in ontario


Englanders are sold by Canadian Tire. I suspect there are a lot of them in Canada. Can you show me any code statement that says wood stoves in Canada will only require ember protection hearths? I think this is a misstatement but am willing to be proven incorrect.


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## fire_man (Mar 31, 2014)

Yea I would like to see that too - about the ember protection.  I can't imagine the  manufacturer's specs for Hearth R value requirements would not apply.


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## fire_man (Mar 31, 2014)

I called USG to ask about Durock Next Gen. as a Hearth underlayment. Their response was: "we have no recommendation". He said his literature specified a max continuous rated temp of 175F, which he personally did not think was adequate for a hearth. He mentioned it was non-combustible, but might not hold up over time under high temp. I think this jives with what others have been told.


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## goofa (Mar 31, 2014)

Begreen where did you find the r value for this particular stove I have searched hotel's online manuals for the r value for the coastline but cannot seem to locate it nor the Oslo.... because I am in the process of my livingroom remodel and never even gave the "r value" a thought for the raised hearth. I'm glad I found this thread pheeeeeeew. I would have had to get out my favorite tool...... the cats paw lol ha


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## goofa (Mar 31, 2014)

*Jøtul


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## begreen (Mar 31, 2014)

It's in the manual for each stove.

_Floor protection 

Floor protection under the Jøtul F 3, must be one of the following:
1. Any non combustible material with an insulative R value of 1.1. 
_
The F500 is ember protection only unless installed in an alcove


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## goofa (Mar 31, 2014)

I looked @ Jøtul's online manual and could not find that for the Oslo or castine


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## begreen (Mar 31, 2014)

Oslo, page 7
_Floor Protection 

Floor protection under the stove must be constructed of a non- combustible material for protection from radiant heat, sparks, and embers. 

Individual sections of floor protection must be mortared together to prevent sparks from falling through to combustible materials. Any carpeting must be removed from under the floor protection. 
_
Castine, page 6
_The Jøtul F 400 requires one of the following three forms of hearth protection:_

_Any UL, ULC or WH listed hearth board. (No bottom heat shield required)._
_Any noncombustible material that has a minimum R- value of 2.0. (No bottom heat shield required.)_
_Any noncombustible material with the use of the stove’s bottom heat shield. _


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## goofa (Mar 31, 2014)

Ok sorry I was only looking at the Oslo I guess. Oops  but it does not specify an R value correct? Just something to protect from embers is that correct in my understanding ?


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## begreen (Mar 31, 2014)

2. describes the R value if there is no bottom heat shield. 

if there is a bottom heat shield then 3. ember protection only.


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## goofa (Mar 31, 2014)

So basically if I want to build a 12" raised hearth for an Oslo out o 2x materials and just cap it with any type of cement board.....hardie board, durarock,etc...... and tile or stone or concrete over that it is fine because a specific r value need not be met ?


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## goofa (Mar 31, 2014)

Yes I see the numerical list as you have quoted in the castine manual but nothing of the likes for the Oslo just ember protection


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## begreen (Mar 31, 2014)

The Oslo is ember protection only, unless installed in an alcove.
_Floor protection under the stove must be constructed of a non- combustible material for protection from radiant heat, sparks, and embers.
_
page 7 for alcove installation
_

The bottom heatshield is required in all alcove installations.


If a listed (UL/ULC) hearth board is not used the hearth

that is constructed must have a minimum r value of 1.6 (see

appendix a). 

_


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## goofa (Mar 31, 2014)

Ok so I guess I am not wrong in my thinking because that's all I was finding thanks


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## skinanbones (Apr 1, 2014)

Begreen I had a moment here at work and did a little digging in my copy of the CSA B365-10.  The general overview of section 8.1 Floor protection state that except when otherwise certified each appliance shall have ember protection and radiant heat protection in accordance with the requirements of clause 8.1.3 and 8.1.4 
Section 8.1.3 deals with ember protection and states that all stoves shall be protected by a continuous durable noncombustible pad that provides ember protection.  The code defines durable as a metal sheet with a thickness of 0.38" or a grouted noncombustible tile on a solid surface.
Section 8.1.4 deals with radiant heat protection and it only applys to units that the firebox is at or closer than 7" and it requires either a course of hollow bricks or custom heat shield to provide the needed protection.  This section of the code when you get into the WETT reference manual is just to deal with uncertified stove ( cookstoves in particular )
There's quite a bit more legalise that I don't feel like typing out but this is the overall feel of the text in referring to ember and radiant protection.


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## Wade A. (Apr 2, 2014)

Just a preference, but I would raise the hearth up a few inches and overhang your finished edge to give it a toe-kick. I did this with mine, and I really appreciate it for a number of reasons. When you sweep off your hearth, it makes it a lot easier to hold a dustpan under the lip than to chase that little line of ash and debris around like you will with a flush hearth. Second, if your knees and back are as old as mine, any amount you can raise up your stove to keep from bending and stooping is a good thing. Third, to my eye,  it just looks better.

To get my R rating, I sandwiched creteboard and micore, topped it with a limestone slab.  I will second the caution about not ever skimping on your R value. I found out that my limestone hearth doesn't even get warm to the touch under my Jotul, but I did it like the specs called for. Even though it was more time and effort, not to mention $,  I don't regret that one bit. The specs are obviously over-engineered, and I don't fault Jotul for that at all. Don't mess around with something like this, for all the obvious reasons. Peace of mind is probably the biggest one.


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## solarstar (Apr 2, 2014)

my hearth:   Over top of 5/8" Existing  subfloor   ...... Add 1/2" plywood, and 1/2" Durock cement Board ,and 1/4" tiles  .  Love it being Flush on the floor..


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## begreen (Apr 2, 2014)

skinanbones said:


> Begreen I had a moment here at work and did a little digging in my copy of the CSA B365-10.  The general overview of section 8.1 Floor protection state that except when otherwise certified each appliance shall have ember protection and radiant heat protection in accordance with the requirements of clause 8.1.3 and 8.1.4
> Section 8.1.3 deals with ember protection and states that all stoves shall be protected by a continuous durable noncombustible pad that provides ember protection.  The code defines durable as a metal sheet with a thickness of 0.38" or a grouted noncombustible tile on a solid surface.
> Section 8.1.4 deals with radiant heat protection and it only applys to units that the firebox is at or closer than 7" and it requires either a course of hollow bricks or custom heat shield to provide the needed protection.  This section of the code when you get into the WETT reference manual is just to deal with uncertified stove ( cookstoves in particular )
> There's quite a bit more legalise that I don't feel like typing out but this is the overall feel of the text in referring to ember and radiant protection.



That sounds similar to US code. It establishes a minimum ember protection usually with metal or tile covered millboard, *except when otherwise certified* (by the manufacturer). To my knowledge the hearth requirement is greater than ember protection in Canada for stoves whose manufactures specify a higher R value hearth requirement as certified by testing. For example, there is no special Canadian spec or optional bottom heat shield for this stove that has an R=2.0 hearth requirement:
http://www.canadiantire.ca/en/pdp/t...e-1800-sq-ft-e-p-a-0642812p.html#.Uzw_EdyIQpE


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## GENECOP (Apr 3, 2014)

Highbeam said:


> Only a fool would build or recommend building something not by the book when the results can so easily be deadly. None of us know how much extra margin for safety any of the minimum specifications has as extra. I cheat on plenty of stuff, but only where the results of failure wont kill anybody.



Agreed , someone like yourself should probably stick to the exact specs as shown by the manufacturer...Some of us do have practical field experience and from this experience have gained a certain amount of knowledge and common sense that allows us to design and modify things to meet our particular needs...if you look around a little you will see that many wood stoves are safely installed over Hearths that do not meet the exact 1.1 R value...even in this thread there is an example....again its probably better someone like yourself does not attempt to think outside the box, but for some of us it is Ok...For the heck of it I sent an Email to Jotul in SCANDANAVIA. Our exchange was regarding the F-3.....1 1/2" of concrete over a combustible surface is OK for the F-3... Might not be the exact 1.1 R value but Mr Odmund from Jotul said it would be fine....


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## bholler (Apr 3, 2014)

Unless you got a written and signed document from them modifying the specs you need to stick with the printed and approved specs.  If you do not you do not meet code if an inspector knows what they are looking for you will fail.  You also are risking any insurance claim having to do with the stove or chimney being denied due to improper installation.  Not to mention that you could burn the house down.  I don't care what experience you have you still need to follow the specs that is what my many years of in the field experience have taught me.


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## GENECOP (Apr 3, 2014)

No problemJ good Luck. .Sendt: 3. april 2014 14:22 Til: Skjønsholt Oddmund Emne: Re: SV: F-3 wood stove question   Thankyou for the quick response .......would 1-1/2" of concrete be a suitable surface to install the F3 on? Thanks... ____________________________________________________________

The format got a little screwed up during the Copy and paste..my question is at the bottom, MR Oddmund from Jotul responded Above....No problem Good luck....


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## bholler (Apr 3, 2014)

Ok who is mr oddmund?  Is he an engineer and did he test that before replying?  does he have the authorization from his superiors to make that modification? and did they then run it by the independent testing facility that approved the original spec?


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## GENECOP (Apr 3, 2014)

bholler said:


> Unless you got a written and signed document from them modifying the specs you need to stick with the printed and approved specs.  If you do not you do not meet code if an inspector knows what they are looking for you will fail.  You also are risking any insurance claim having to do with the stove or chimney being denied due to improper installation.  Not to mention that you could burn the house down.  I don't care what experience you have you still need to follow the specs that is what my many years of in the field experience have taught me.



The original conversation was not about insurance companies and inspectors....Thousand of people install wood stoves every year without the involvement of insurance companies and inspectors...the OP simply asked for suggestions on how to accomplish something...I maintain that my original Approach would be safe and also meet the OPs  needs, Jotul confirmed what I already now...If the conversation had been about inspectors and insurance my advice would have been different...



bholler said:


> Ok who is mr oddmund?  Is he an engineer and did he test that before replying?  does he have the authorization from his superiors to make that modification?



Not sure, I will now begin a full investigation to find out the Jotul Guys Title in the company and his posistion in the company!   

Look, at the end of the day everyone has to do what they are comfortable with....I know what works for me does not work for everyone....Have a good night....


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## Grisu (Apr 3, 2014)

GENECOP said:


> if you look around a little you will see that many wood stoves are safely installed over Hearths that do not meet the exact 1.1 R value



They are not safely installed, they may not  have led to any accidents so far (at least to your knowledge; I am wondering how many dead people are posting here that being skimpy on the hearth requirements was NOT the best thing to do.)


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## begreen (Apr 3, 2014)

Here are a couple examples of floors under safe hearths, that weren't. All stoves are not created equal. Neither should their hearths be.


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