Hearth Extension Help For Fireplace Insert

[GoodNeighbor]

I'm looking for ideas on replacing the current hearth extension for our insert. Right now it's the fake stone which is very uncomfortable to kneel on:

Plus, it's crumbling apart:

It's 25" from the front of the insert and 60" wide. It's laid on some kind of fake wood subfloor:

Our idea is to pull all the rock and mortar up, lay down some kind of cement board and tile. But cutting tile to match the curves could be tricky. The other idea is to just mix up a bag of Quikcrete and dump it in. (It's an inch deep.)

If we go the Quikcrete route do we need a special kind of concrete? And could/should we pour it over the subfloor or should there be some kind of heat barrier also?

Thanks for any and all suggestions/help/guidance.

Dean

Update: Just found the manual and it says "a non-combustible hearth extension equivalent to 3/8" millboard (R=.75, C=1.3, K=0.5) must be used. If the unit is to be installed without a raised hearth, it must extend 24" in front of and 8" beyond the sides of the fuel opening."

 

[begreen]

It looks like there is a good chance that besides being inconvenient, the hearth was poorly done and it not providing adequate thermal protection. I would remove the old, then cut out the new hearth, to the subfloor, not following the old hearth outline, but honoring the proper hearth requirements. This will give you a straight-edge space that will be easy to tile. The new hearth can be then built up to spec, meeting the R value requirement and tiled.

 

[GoodNeighbor]

Nothing in this house was done properly we're finding out. I think what we'll do is since we're tearing it out anyway, we might as well do it right. The only problem with the flush hearth is that to get the R value needed we're going to have to take it down pretty far because we'll need at least a couple of layers of cement board.

Dean

 

[DAKSY]

Nothing in this house was done properly we're finding out. I think what we'll do is since we're tearing it out anyway, we might as well do it right. The only problem with the flush hearth is that to get the R value needed we're going to have to take it down pretty far because we'll need at least a couple of layers of cement board.

Dean

Not if you use 1/2" Micore. One layer with 1/4" hardibacker, thinset & your 3/8 tile & you should be good to go.
Forget the cement board. You'll need 2.5" to get the R value you need.

 

[GoodNeighbor]

Thanks Bob. I was starting to get confused with all the different materials, thicknesses, R values, etc. This makes it simple, other than finding the Micore.

 

[jocam]

I am looking to do the same hearth re-work. What is Hardibacker? Is Micore like cement board? Can it be tiled over? I am from Ontario and am not sure these material are available at Home Depot. Where would I look?

 

[firefighterjake]

I am looking to do the same hearth re-work. What is Hardibacker? Is Micore like cement board? Can it be tiled over? I am from Ontario and am not sure these material are available at Home Depot. Where would I look?

Haribacker is a cement board . . . Micore is an insulative material . . . Hardiboard could be tiled over . . . Micore cannot have tile directly fastened to it.

You may find Hardiboard or similar cement boards at the Home Depot . . . I doubt you will find Micore there . . . finding Micore can sometimes be more of a challenge.