micore and marble installation question

[annieheat]

Hi:

We have finally made a decision on a stove and (gulp) accepted the cost for the chimney we will need. We will be installing a hearthstone heriatage. We will have the rest of the installation contracted out but are planning on installing the hearthpad ourselves -- very soon.

I have reviewed the r value and size of hearth needed for our stove, bought our micore and scrounged a large slab of marble out of a family member's garage.

MY QUESTION IS .... that my husband and I are not sure (read debating over ) whether or not we need to also use durrock in addition to the micore for its stability and hardness so that the weight of the stove does not put too much pressure on the marble and cause it to crack. To add more detail, we know that our floors are not totally level in our nearly 150 year old house and the "subfloor" in our house is made up of 5" wide pine planks that are tongue and grooved together. Can we just use a leveling compound and skip the durrock or would others recommned the added strength and stability of the durrock?

Any other suggestions or recommendations on micore intstalltion? When I went to pick it up I was surprised at what at soft material it was.

Thanks very much!

 

[Nokoni]

I am not an expert on this but I can tell you what I did. I live in an 1895 house with old wood floors and I put Micore 300 down and then put one big piece of slate over that. I used mortar to affix it. My stove is a Jotul F3 and weighs I think about 250 pounds. I have not had any problems with the slate cracking. I was worried about it though. When they installed the stove they had to move it around a lot on the slate and it did make small marks on the slate which I don't mind. I think slate is softer than marble. I'm sure others can advise you on this. Good luck!

 

[wg_bent]

Durock is SOOOOO cheap, why bother the debate, just put it in and move on. I think it's under 10 bucks a sheet.

 

[annieheat]

Its true durrock is cheap but the issue is not the cost but the thickness because we are trying to keep the profile of the hearth pad a low as is possible, but yes I guess the safer route involves the durrock.

thanks

 

[annette]

If I've absorbed the info properly from over on the tile site I visit, the important thing is to have full support and no voids. If you use self-leveling compound, that should do it. It will support the micore fully, the micore will support the marble, and as long as you don't drop the stove onto the marble, things should be good!

That tile site is full of helpful tile experts who should be able to settle the question, and probably give advice on the best product to use for leveling the floor. It's the John Bridge Tile Forum--I always just Google "john tile" and click.

Good luck on your project!

 

[wg_bent]

You can get 1/4 durock for a little lower profile.

 

[babalu87]

Want to build a hearth pad that will pass any inspection and never worry about cracking?
Build with these layers

3/4" plywood
Micore 300
Durock
Stone/tile
Trim out with stone tile etc.

Build it where it will sit
I built mine in my basement, good thing my neighbors son is a big stong kid

 

[Nokoni]

Its true durrock is cheap but the issue is not the cost but the thickness because we are trying to keep the profile of the hearth pad a low as is possible, but yes I guess the safer route involves the durrock.

thanks

This was my issue too. My stove is in a small room and I didn't want a tall hearth. I had to cut into the newer wood flooring to get to the old wood floor so that my profile would be lower. In the end the hearth only comes up less than 1/2" so it blends really well into the room. I did use a trowel with big notches, I forget the exact size, so that there would be a good support of the thin set for the slate to sit on.

 

[bcnu]

I am also putting in a hearth pad and I like Babalu87's recipe. Can I eliminate the micore and use two layers of durock instead? Durock available locally but the micore is 30 mile away.

 

[babalu87]

I am also putting in a hearth pad and I like Babalu87's recipe. Can I eliminate the micore and use two layers of durock instead? Durock available locally but the micore is 30 mile away.

In a word, no

One way or another you need it to have the K value required by the stove.

See if you can get your lumber yard to order a sheet of micore for you.