Micore Board Strong Enough?

[Rob From Wisconsin]

Looking to "beef up" my hearth.
Is Micore board strong enough to support my 300lb+ stove
without breaking? I've never worked with the stuff before,
so I'm a bit "green" to it. Thanks!

 

[DAKSY]

Looking to "beef up" my hearth.
Is Micore board strong enough to support my 300lb+ stove
without breaking? I've never worked with the stuff before,
so I'm a bit "green" to it. Thanks!

Nope. It's pretty fragile. The BEST thing to do is to sandwich it between Dura rock or hardi backer (top) & Plywood (bottom), at least if you intend to move it at a future date. If not, you can probably omit the bottom plywood layer & screw right through the top layer to the floor under the Micore. Stone or tile or whatever can then be applied to the top layer with thinset...

 

[Rob From Wisconsin]

Thanks for the quick response.
Sounds like I could just place Cement Board on top of it,
and that would be OK??

 

[DAKSY]

Thanks for the quick response.
Sounds like I could just place Cement Board on top of it,
and that would be OK??

Probably, but that depends on whether your stove has legs or a pedestal. The legs may eventually push right thru the concrete board. You have a heavy weight distributed over a very few square inches of surface. The board is meant to be a backer not a finished surface. I'd at least try to find some casters, tiles or stone pieces to distribute that weight over a greater surface area. Your call.

 

[Wood Duck]

It depends what is under the cement board, i think. With a suitable support under the cement board and tile or something like that on top, yes, the cement board will be fine.

 

[dorkweed]

I built my raised hearth out of 2x4's (about 12" on center), 1/2 plywood over that, and 2 layers of 1/2" Micore over that, 1 layer of 1/2 Durock next gen over that and then my mortar and procelain tiles. The 13NC goes about 300lbs., and my hearth takes it no problem. No sagging or deflection when stepping on it that I can see or feel.

 

[DAKSY]

It depends what is under the cement board, i think. With a suitable support under the cement board and tile or something like that on top, yes, the cement board will be fine.

He's putting the cement board on the Micore....There's not much support from the Micore unless it's on a solid surface. No way would I install Micore on a 2x (anything) framework without ply below...

 

[Fire Breathing Dragon]

I built a hearh ealier this year with Micore. Installed it directly over the OSB subflooring, then a layer of sheet metal to disperse the heat, then topped it with 1/2 cement board staggering the seams. On top of the cement board I installed ceramic tile in a bed of thinset. My stove is the VC encore on pedistal legs and had no movement since installed in Feb this year. As said before Micore has no structural strength, it is like using a sheet of drywall which can crush ever so slightly but with good cement board, tile, and thinset above it should disperse the weight... Good luck!

 

[mepellet]

I built a hearh ealier this year with Micore. Installed it directly over the OSB subflooring, then a layer of sheet metal to disperse the heat, then topped it with 1/2 cement board staggering the seams. On top of the cement board I installed ceramic tile in a bed of thinset. My stove is the VC encore on pedistal legs and had no movement since installed in Feb this year. As said before Micore has no structural strength, it is like using a sheet of drywall which can crush ever so slightly but with good cement board, tile, and thinset above it should disperse the weight... Good luck!

How about installing 2 layers of micore directly on the subfloor and then tiling directly on top of that? What is the recommended way of attaching micore to the subfloor?
Is the layer of sheet metal and the cement board necessary?

 

[begreen]

How about installing 2 layers of micore directly on the subfloor and then tiling directly on top of that? What is the recommended way of attaching micore to the subfloor?
Is the layer of sheet metal and the cement board necessary?

Uh, uh, no way. Micore is not a suitable substrate for tiling. Put a top layer of cement board (preferably two sheets thick) on top and screw through the layers to attach to the floor. Most cement board mfgs recommend a screw every 8".

 

[begreen]

Rob, if you have a pedestal base, maybe. But if the stove has legs and for a more durable surface at least put a sheet of 24 or 22 ga metal on top of the cement board and screw it down at the corners.

 

[mepellet]

Uh, uh, no way. Micore is not a suitable substrate for tiling. Put a top layer or two of cement board on top and screw through the layers to attach to the floor. Most cement board mfgs recommend a screw every 8".

Thought so. Just wanted to check since I have not bought the Micore yet. I had no idea what it was like.

 

[begreen]

It is a soft spongy material, kind of like what you would find in acoustic tiles. It's used for sound deadening in office cubical dividers.

 

[mepellet]

It is a soft spongy material, kind of like what you would find in acoustic tiles.

Ok. Thanks again begreen! I think I'll go with:
Tile on top of 1/2" cement board (R0.39) on top of 1/2" micore (R1.03) on top of the existing subfloor (diagonal boards on joists) for a total of R1.42 plus whatever tile is worth (not much I assume)

 

[begreen]

Tile is not worth much for insulation unless very thick. What stove is going on top of this?

Nevermind. I see you have your own hearth building thread going.

 

[mepellet]

Tile is not worth much for insulation unless very thick. What stove is going on top of this?

Don't mean to hijack the thread. But now it's a napoleon 1100c but I want the hearth to be as flush as possible with the existing flooring and for it to have as much R value as possible to accomodate a large variety of stoves should we decide to replace the 1100c. I had started a thread earlier today about the hearth build.

https://www.hearth.com/talk/threads/new-hearth-build.109188/