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".

 

[begreen]

Also make sure the Durock is not the stuff for showers. That can have styrofoam beads in it instead of pumice. The regular cement board with edgeguard is ok.

 

[faultymechanics]

Also make sure the Durock is not the stuff for showers. That can have styrofoam beads in it instead of pumice. The regular cement board with edgeguard is ok.

Uhhh, how do I tell? I linked the stuff i was looking at above. Any chance you can tak3 a quick look at the link and confirm?

 

[begreen]

That looks ok. They keep changing their product line so it's hard to keep up. Watch for white beads on the raw edge.

 

[faultymechanics]

Thank you for your help.

I got the all clear from my installer that he can pull the old insert ahead of time. Hoping end of this week he can pull it and then next week I can demo the old extension. That will give me time to make my plan for install of new hearth.

Micore and durock seem simple enough, never done tiling before so that will be an experience I'm sure.

 

[bigealta]

Layout your tiles

Thank you for your help.

I got the all clear from my installer that he can pull the old insert ahead of time. Hoping end of this week he can pull it and then next week I can demo the old extension. That will give me time to make my plan for install of new hearth.

Micore and durock seem simple enough, never done tiling before so that will be an experience I'm sure.

Lay out the tiles you are using on the floor before you start building base, and then build the base so that you don't need to do any cuts.

 

[faultymechanics]

Should I put anything between the trim around the edges of the new hearth extension and the layers of material? I imagine I don't want any gap because an ember could fall between to the two(in theory).

Is there any reason to put thin sheet metal between or under any layers? I feel like I've seen mention of that on this forum.

 

[bigealta]

You can use the grout you use for tiles, but better would be a matching "caulk" that the tile store will sell you when you get the grout.
It's used in corners of backsplashes and the countertop/backsplash corner, and the top of the tile backsplashes where they meet the bottom of the cabinets.

The caulk is more flexible than the grout so it reduces cracks at those locations.
The tile store can advise you on color matching the caulk and grout.

I did the sheet metal between 2 layers of "mineral"? board if you read my post a few above, but now the code is different than 40 years ago.

 

[faultymechanics]

You can use the grout you use for tiles, but better would be a matching "caulk" that the tile store will sell you when you get the grout.
It's used in corners of backsplashes and the countertop/backsplash corner, and the top of the tile backsplashes where they meet the bottom of the cabinets.

The caulk is more flexible than the grout so it reduces cracks at those locations.
The tile store can advise you on color matching the caulk and grout.

Is it heat safe? For example would I want a line of it between the extension and bottom brick of the actual fireplace(not in front of the opening) so there is no gap. Kind of like where your kitchen counter meets your backsplash, that idea.

 

[bigealta]

The standard grout caulks are not rated as high heat resistant, but that said i'd have no problem using it on the perimeter of the extension.
Directly under a woodstove? For my f400 that would be no problem as the floor barely gets warm running 24/7.
But other stoves i can't say.

 

[begreen]

The insert does not have legs so the firebox is closer to the hearth level. A lot of heat will radiate from the front door. The hearth will get hot after hours of steady burn.

As long as it is beyond the required hearth extension distance rimming the hearth edge can be done with wood, or it can be metal, or a bull nose tile to finish off.

 

[faultymechanics]

The insert does not have legs so the firebox is closer to the hearth level. A lot of heat will radiate from the front door. The hearth will get hot after hours of steady burn.

As long as it is beyond the required hearth extension distance rimming the hearth edge can be done with wood, or it can be metal, or a bull nose tile to finish off.

In regards to your first statement, would that imply that I should use grout(even though not ideal) between the hearth extension edge closest to the fireplace and the actual fireplace surround? That's what they previously did but obviously due to expansion and contraction, it cracked the grout out.

 

[begreen]

To be proper, the hearth floor in the fireplace and the hearth extension, should be one continuous cement base that is reinforced with metal (rebar or mesh).

Thread 'help with rebuilding hearth'

Jan 25, 2023

We recently purchased a 1925 home in Philadelphia, and we're having a wood-burning insert professionally installed in early March (it was the earliest they could get to us). However, I've needed to do some demolition of the old mantle (a super ugly 2x4, drywall, and mirror monstrosity) and hearth to get it ready for the installers. We have a 2" piece of slate countertop we're going to use for the hearth extension, but the more I dug into the work around the hearth--literally and metaphorically--the more questions I had.

The hearth extension doesn't seem to be connected to the hearth...

• A Stove in Philly
• Replies: 10
• Forum: The Hearth Room - Wood Stoves and Fireplaces

Post in thread 'Hearth extension is not supported nor attached?'

Jul 31, 2023

Cement board to close fireplace, 3/4" plywood for hearth extension, level frame around extension, will use that as a guide.



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Learn from our mistakes: down't mix 2 bags at a time, it takes too much effort to do this. It's easier and faster to mix one bag in a wheelbarrow.
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