Hearth pad extension questions

[faultymechanics]

Current stove being replaced before years end to get tax credit. It appears thebold stove had an r value requirement of around .5 so I am assume that's what is currently there.

New stove we want is a rating of 2.1. Im struggling to figure out a reasonable way to hit that r value. I was thinking of 1" of micore 300 plus a 1/2" of cement board and finishing with tile, however I'm struggling to find what cement board is safe to use.

My other thought is to use another hearth pad extension like you can find from HYC on top of our. Current, slightly raised hearth extension. Is that going to look tacky/like trash?

I finally have the budget, means and reas9n to get a stove in but I'm falling short with the extension and could use help to make this final push.

Photo of current extension(definitely worked over and needs some love).

Chatgpts rough attempt and showing what it could look like with the hearth pad(it got the sizing very wrong but sort of portrays the idea I was thinking of.

 

[begreen]

What is the new insert that's going in?

 

[faultymechanics]

Ci2700 or hi500.

If we had to because of R-value, my wife would probably accept the osburn 3500.

 

[Ctwoodtick]

my first thought would be to make sure you have the required length of hearth extension from stove (whether 16 inches or whatever).
After that, an appropriately rated hearth pad would be the easiest thing to do. What you have in the picture looks good I think. As a side note, I wonder what is under your existing hearth extension. If there is no combustible old wooden forms, framing, insulation, etc, I suppose the hearth protection is theoretically not needed. Not sure if you could confirm those clearances though. Not to mention that code is code and no harm by using that hearth pad in picture.

 

[faultymechanics]

my first thought would be to make sure you have the required length of hearth extension from stove (whether 16 inches or whatever).
After that, an appropriately rated hearth pad would be the easiest thing to do. What you have in the picture looks good I think. As a side note, I wonder what is under your existing hearth extension. If there is no combustible old wooden forms, framing, insulation, etc, I suppose the hearth protection is theoretically not needed. Not sure if you could confirm those clearances though. Not to mention that code is code and no harm by using that hearth pad in picture.

So the form was unfortunately left in place when the home was built in the 30s, otherwise I wouldnt stress it.

In regards to the length, the entire extension from fireplace brick forward is 19", the current winterwarm insert definitely isn't, and wasn't, up to code. New insert will be more flush.

 

[faultymechanics]

I have a new plan but need some questions answered.

Is this the Durock next gen product that I can "safely" use over micore to make a new extension: Durock?

If so, can I replace my current extension with TWO 1/2 layers of micore 300, a 1/2" sheet of this durock and then tile? Would that be appropriate for r-2.1?

Additionally, another thought, could I do exactly what is described above but just add it on top of my current extension and then just trim it in? I recognize I'd have probably a 2" lip between the extension and the floor.

Thoughts?

 

[faultymechanics]

And another question, if I went with the hearth pad, would I be tucking it slightly under the front of the Regency CI2700? It pokes out about 3.5" and the hearth pad would be 18" deep and 1" high. It appears the air intake on the CI2700 is 3/4" tall and on the bottom of the stove so I wouldn't want to block it with the pad.

 

[begreen]

Ci2700 or hi500.

If we had to because of R-value, my wife would probably accept the osburn 3500.

Got it. The CI2700/HI500 require a hearth value of 2.13 if the the hearth is not at least 6.5" above floor level. The Osburn 3500-i requires R=2.0 in this case and it must extend 27" in front of the stove door.

If a stock hearth pad is used like shown, then the insert also needs to be raised for the equivalent hearth pad thickness. This can be done with cement board, brick, etc. Another option is to build a custom hearth extension that meets or exceeds the required R value. Usually, in that case a sandwich is made which includes a layer of Micore board.

 

[bigealta]

Does anyone know what the old 1/4" 3'x5' sheets were called?
I thought it was mineral board but that seems to be an insulation board now?
The boards i'm asking about were very similar to 1/4" hardie backer board, but flat on both sides.

I'm asking because when i installed a VC defiant 40 years ago, the local code inspector wanted 1 layer of these boards screwed down to the wood below with the screws on the perimeter only, then a sheet of sheet metal, then a top layer of the 1/4" board screwed down on the perimeter only again, then tile on top.

I don't think this is good for code anymore but i just can't remember exactly what that board was?
I did get it at a local builders supply yard.

 

[faultymechanics]

Got it. The CI2700/HI500 require a hearth value of 2.13 if the the hearth is not at least 6.5" above floor level. The Osburn 3500-i requires R=2.0 in this case and it must extend 27" in front of the stove door.

If a stock hearth pad is used like shown, then the insert also needs to be raised for the equivalent hearth pad thickness. This can be done with cement board, brick, etc. Another option is to build a custom hearth extension that meets or exceeds the required R value. Usually, in that case a sandwich is made which includes a layer of Micore board.

Okay, so a custom extension will need to be done then.

In that case, would you say, 2 layers of 1/2 micore, 1/4" durock and a non combustible tile would be suitable?

Should I build it directly on top of the existing extension or remove the current extension and build the new one in its place?

Just looking for your personal opinion.

 

[faultymechanics]

Is there a special screw i can use to connect the durock to the masonry fireplace? I dont have plywood going underneath my extension and I need to connect the cement board to the masonry underneath.

Also, once I do this, the hearth extension may be .5" or so higher than the hearth where the insert rests. Is that okay? Is there any adjustment for that? Do I need to put layers of durock under the insert to level it with the extension?

 

[begreen]

Okay, so a custom extension will need to be done then.

In that case, would you say, 2 layers of 1/2 micore, 1/4" durock and a non combustible tile would be suitable?

Should I build it directly on top of the existing extension or remove the current extension and build the new one in its place?

Just looking for your personal opinion.

That's the general idea but definitely use at leat 1/2 cement board on top. Micore is soft and tile joints may flex with just a 1/4" underlayment.

 

[faultymechanics]

That's the general idea but definitely use at leat 1/2 cement board on top. Micore is soft and tile joints may flex with just a 1/4" underlayment.

Ordered my micore(i get to drive 3 hours round trip for it! Oh boy) and plan to grab durock locally, will make sure its 1/2".