Hearth pad build theory: where should Micore be?

[brider]

Thinking about my hearth pad:

Does it matter that the Micore 300 layer in my hearth pad build will be sandwiched between the Durock and the 3/4" plywood? Or should the upper tile surface be set right on top of the Micore? I suppose if it's purely thermal conductivity we're considering, then I could consider the tile and Durock as perfect conductors, and the Micore will then do it's job when the heat hits it. I am concerned, though, about the actual HEAT that the Durock will see, being just underneath the tile. Is this a concern, or should I shut my yap and just build the thing?

 

[pinewoodburner]

Thinking about my hearth pad:

I am concerned, though, about the actual HEAT that the Durock will see, being just underneath the tile.

The durock can take the heat, built it.

 

[begreen]

You always want the durock on top as a stiff underlayment for the tile and for good bonding. Micore is too soft, won't bond well.

 

[fossil]

What's important are insulating value to protect the combustible underlayment, the structural integrity of the sandwich, and a good bonding surface for the tile. The micore provides most of the insulation, and it just needs to be between the floor and the stove. The Durock provides stiffness and crush strength and the tile bonding surface...it needs to be just beneath the tile. Put the Micore on the bottom, then the Durock, then the tile. Durock is non-combustible, it's just not a real good insulator. You don't have to be concerned about the Durock getting hot. Rick

 

[Tfin]

You always want the durock on top as a stiff underlayment for the tile and for good bonding. Micore is too soft, won't bond well.

Ditto that. Plywood base, Micore, Durock, then tile (followed by some sort of trim around the edge for aesthetics). Hearthpad done.

 

[rwilson]

I’m building a hearth pad right now as well. I was planning on using ceramic tile on top of durarock on top of micore on top of plywood… Do I need to use any bonding (mortar) between the micore and durarock? What about fastening the micore to the plywood?

 

[Tfin]

I’m building a hearth pad right now as well. I was planning on using ceramic tile on top of durarock on top of micore on top of plywood… Do I need to use any bonding (mortar) between the micore and durarock? What about fastening the micore to the plywood?

No morter, but you do want to secure it. You want to use Durock screws of proper length, so that they go down through the Durock, Micore, and secure into the plywood (without comming out the bottom).

 

[rwilson]

Thanks for all the info. I am building a corner hearth pad that is 5'x5', so I will have to cut the Durock and butt 2 pieces together. Do I need to cement those 2 pieces together?

 

[Tfin]

I didn't. I simply butt the two piece of Durock together and applied screws around the edges and in the middle of each section. Remember you're then going to have adhesive on top of all the Durock to secure the tile to each. So that helps to secure everything as well.

The pad can be quite heavy when completed, so If you don't have help in moving it, I recommend you build it in place.