brick on top of Micore

dtabor said:

Im making a simple hearth for my wood stove. Question is, can I put the brick right on the Micore or will I have to have some sort of cement board between them?

D

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Are you talking about a hearth pad? You need to know the R value required (see your stove owners manual) then add the r-value of the micore and the brick to see if its acceptable - my guess is that you will need the cement board just to bump the r-value up enough, but its also useful to give the platform some stiffness. Micore is not a good backing for anything, if you are going to walk on this thing then you are going to want the cement board on top (and maybe even on both sides) of the micore.

I'm using 1/2" of durock on top of 3/4" of Micore.

The R-value question aside, I'm thinking the micore may be a little too soft of a material for the relatively small footprint of the bricks (especially with a stove on the brick), though it might be ok with tile. (I'm thinking more cracking than anything else) I think I would go the safer route and put a layer of durock on top of the micore before the brick.

I agree, the durock or other cement board is cheap, just put a layer of it on top to ensure you don't have problems (note, I think TWO layers of micro makes it even MORE likely that the thing will crack when you put the stove on it).

Plywood or concrete board/Micore/Cement board/Brick or tile or stone
Micore will soak up the water in the grout

I wanted the hearth flush with my new floor. Must have measured wrong somewhere. Put down two layers of 1/2" micore 300. Thought I would have room for 1/4" cement board and then tile - but can only do the tile. The Micore seems pretty stiff - so hope it works. Since only Micore downright now, makes me think I should remove a layer and put down the cement board for added stiffness. Stove we're looking at weighs 425 lbs.

That's what I would do bcnu. I can't imagine you need both layers of micore to meet the necessary thermal resistance.

dtabor, I would definitely put a layer of cement board over the Micore. Besides being used for its R-value in hearths, it is also popular in office cubicles, as one of its qualities is that you can easily put thumbtacks in it. VERY squishy stuff, we worried about breaking it just installing it between plywood and cement board on our hearth. If you only need .59 R value, why would you use two layers of Micore 300 for a total of 2.33 R-value? Skip one layer of Micore and put cement board on top instead. I can't imagine the stove being installed without someone stepping on the hearth in addition to all the weight of the stove being put there. Let me repeat, Micore is really squishy, it isn't strong or sturdy at all.

I just stepped on my 2 layers of micore and it feels really solid. Pressed hard with my thumb and no give. Could even jump up and down and it would be ok. However, I'm not a 400 pound wood stove. I do agree that it seemed pretty flimsy when handling and cutting.

Its not people stepping on it that worries me, its the weight of the wood stove, which is probably on legs and therefore the weight of the stove is being distributing over very small areas. In other words, you've got four hundred pounds of stove interfacing with the hearth via those tiny little legs that probably have a bottom surface area of .5in^2. Divide the weight of the stove by four and then divide that number by the surface area of the leg touching the hearth and you'lll see there's quite a bit of pressure sitting on the hearth at those points.

Micore wasn't made for applications like this, as said earlier, and it definitely isn't supposed to have tiles stuck to it. Water will turn it into a kind of weird slurry on the surface, and the last thing you want to happen is for a tile to lift after you've gotten the whole thing laid down and looking good.

I'm gonna agree with you Corie. I don't want a problem later that can be corrected pretty easily now. I'll remove one layer of Micore and put on the cement board and tile on top of that. The r value will still be above the requirements and I won't have to worry about future repairs. That's one of those win-win situations.