Fireplace installation HELP!

[Dave48103]

So we waited until the new Montecito Estate fireplace came out this summer to complete our project. It was installed into the rough framing last week, all went perfect. Until we noticed in the new installation instructions from Astria that they are now asking for a 1/2" non-combustible base for the fireplace. The previous instructions allowed a combustible base. We used Permabase cement board which is "technically" not non-combuatsable to ASTM E136, even though it has a 0 flame sread and 0 smoke development. Our fireplace installer said it was still safe, which I agree, but I'm worried that the inspector won't pass it. I obviously don't want to tear the whole thing out and start again. I was thinking about sliding 24 gauge sheet metal under the unit to act as a non combustible barrier, and add to the safety factor.

All the other equivalent wood burning fireplaces from Napoleon, Fireplace Xtrordinair and Heatilator, all allow a combustible base, including plywood, under the unit. I can't understand Astria's rationale and have been trying to contact them to get a better read on all this. The base is safe as is, and adding sheet metal would improve it. My installer was unaware that Atria changed their requirement, but they also weren't the ones who put the base down, our general contractor did that. I can't imagine that it's a heat concern under the fireplace as there is about a 6" air space under the firebox to the bottom of the unit that has the fans and all the electrical wiring for it. If that space gets hot, I have bigger issues that what's under the fireplace.. Can anyone shed any light on my situation? Thanks for your input, i'm just trying to avoid spending a few thousand dollars to redo all this.

 

[begreen]

Permabase is meant for wet areas like showers. It has polystyrene foam beads in it instead of the pumice in Durock NexGen.



That said, their literature does show it being used on the face of a ZC fireplace. Your best bet would be to call their tech support to verify it being ok for this specific application.
https://www.nationalgypsum.com/File/110831.pdf
(1-800-628-4662),
8:00 a.m. - 4:45 p.m. EST,
Monday-Friday

 

[Dave48103]

Permabase is meant for wet areas like showers. It has polystyrene foam beads in it instead of the pumice in Durock NexGen.

View attachment 188708

That said, their literature does show it being used on the face of a ZC fireplace. Your best bet would be to call their tech support to verify it being ok for this specific application.
https://www.nationalgypsum.com/File/110831.pdf
(1-800-628-4662),
8:00 a.m. - 4:45 p.m. EST,
Monday-Friday

Already did that. All they would comment on, is that it is not considered "non-combustible". They say it's up to fireplace manufacturer and code as to its suitability and specific applications. Their product actually has a higher heat exposure factor of 220° versus Durock which is only 200°, making it actually a little safer than Durock. At this point, I still feel like it's a safe installation, just trying to figure out how to get it to pass inspection. That's why I was thinking the sheet-metal solution might help.


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[zenoparadox]

That's why I was thinking the sheet-metal solution might help.

I can't see how this would help. Maybe I'm not reading you correctly, or I'm not thinking correctly but you said the installation needs 1/2" of non-combustible material under the fireplace. My understanding is that when installation instructions say this, they mean that the entire thickness must be deemed non-combustible to meet requirements. If the permabase is deemed combustible then adding a sheet of 24 gauge metal on top of it won't fix the problem because most of the thickness will still be permabase, which is deemed combustible.

 

[kennyp2339]

My take is that the way codes are enforced is compairing the install requirements, if the install book says permabase cement board is good then the inspector should honor it.

 

[zenoparadox]

My take is that the way codes are enforced is compairing the install requirements, if the install book says permabase cement board is good then the inspector should honor it.

That's how they did it here. The inspector went by the instructions. There was one clearance to combustibles that was not okay, we fixed it, and that was that. Luckily, the fix for us was super simple.

 

[bholler]

My take is that the way codes are enforced is compairing the install requirements, if the install book says permabase cement board is good then the inspector should honor it.

Yes but if it has polystyrene beads in it they could combust or melt and release some nasty fumes. Just because it passed inspection does not mean it is safe. Inspectors miss stuff many times and they are not liable for what they miss either. So it is on the installer and or the homeowner. I would call the manufacturer of permabase to check things out.

 

[Dave48103]

I can't see how this would help. Maybe I'm not reading you correctly, or I'm not thinking correctly but you said the installation needs 1/2" of non-combustible material under the fireplace. My understanding is that when installation instructions say this, they mean that the entire thickness must be deemed non-combustible to meet requirements. If the permabase is deemed combustible then adding a sheet of 24 gauge metal on top of it won't fix the problem because most of the thickness will still be permabase, which is deemed combustible.

The code does allow for alternate means of achieving equivalent non combustible surfaces. I realize that ideally I should replace the permabase with durock, but doing so would mean removing the fireplace and the venting above in order to do this.

In reality, ASTM E136 is the standard for non combustible materials, However, in practicality, this really addresses the structural integrity of a product when subjected to 750 degrees. In a wall application this is crucial for cement board, so the wall does not collapse. In this application, the worst that would happen is that the cement board might compress a bit. This material has a tested flame spread of 0, which means it does not burn.

I'm also trying to figure out from Astria why this is the only FP in their EPA certified line that asks for a non combustible material under the unit

 

[bholler]

In this application, the worst that would happen is that the cement board might compress a bit. This material has a tested flame spread of 0, which means it does not burn.

Yes but if it compresses a bit then you no longer have 1/2" of protection. And what about that foam offgassing?

I'm also trying to figure out from Astria why this is the only FP in their EPA certified line that asks for a non combustible material under the unit

No idea you would have to ask them. But I am sure there is a good reason especially since it is not just a blanket company policy.

 

[begreen]

Permabase is very unlikely to compress. If it did it would be a lousy substrate for a tile floor. In the manual it looks like the Lennox Montecito estate did not require cement board under the fireplace but does require 1" cement board (2 layers) for the hearth. This makes sense, it's likely to see the most heat there.

I just downloaded the manual for the Astria Montecito Estate and the requirement for the cement board is not under the fireplace, just 1" for the hearth.

 

[bholler]

Permabase is very unlikely to compress.

It might if that polystyrene melted But it doesn't look like it is an issue just put regular cement board under the hearth problem solved.

 

[Dave48103]

Permabase is very unlikely to compress. If it did it would be a lousy substrate for a tile floor. In the manual it looks like the Lennox Montecito estate did not require cement board under the fireplace but does require 1" cement board (2 layers) for the hearth. This makes sense, it's likely to see the most heat there.

I just downloaded the manual for the Astria Montecito Estate and the requirement for the cement board is not under the fireplace, just 1" for the hearth.

View attachment 188719

Where did you download that from? The instructions I have from their website show non combustible under the unit

 

[Dave48103]

It might if that polystyrene melted But it doesn't look like it is an issue just put regular cement board under the hearth problem solved.

Yes, I'm using durock for the hearth, the issue is only under the unit

 

[begreen]

Where did you download that from? The instructions I have from their website show non combustible under the unit

http://woodstoves.net/documents/Astria/900118-00_NC_Montecito_Estate_EN_IICO.pdf

 

[Dave48103]

Yes but if it has polystyrene beads in it they could combust or melt and release some nasty fumes. Just because it passed inspection does not mean it is safe. Inspectors miss stuff many times and they are not liable for what they miss either. So it is on the installer and or the homeowner. I would call the manufacturer of permabase to check things out.

Agreed, I checked the Material Data Sheet for the product. No specific hazard listed from the beads, even when heated/melted. Believe me, I'm the homeowner, and an architect, safety is my one concern, that's why I'm trying to come up with an equivalent safe system that will meet everyone's approval. I'm not looking to have the mechanical inspector miss anything

 

[bholler]

Agreed, I checked the Material Data Sheet for the product. No specific hazard listed from the beads, even when heated/melted. Believe me, I'm the homeowner, and an architect, safety is my one concern, that's why I'm trying to come up with an equivalent safe system that will meet everyone's approval. I'm not looking to have the mechanical inspector miss anything

And honestly I have no idea if it could cause an issue either the manufacturer would know better than anyone. I would also call the stove manufacturer to confirm what is needed under the stove itself because there seems to be some conflicting info.

 

[begreen]

So it looks like this might just be a poor documentation error. I went to Astria's site for the latest manual. It shows the same drawing, but someone added the non-combustible requirement, but the illustration shows no change in the cross-hatching for normal flooring.
Agree with bholler, call Astria. From what I see I am tending to concur with your original assumption. BIS has made this fireplace for over a decade (even though sold by Lennox and now Astria). This requirement is new. Why?

FWIW I don't understand why permabase was used by the contractor under the fireplace when durock was used for the hearth. What was he thinking?

 

[Dave48103]

http://woodstoves.net/documents/Astria/900118-00_NC_Montecito_Estate_EN_IICO.pdf

Ahh, that was our confusion as well, they updated their instructions this month, after we installed the platform, but before we installed the fireplace. If the fireplace was installed a few months ago, then there wouldn't be an issue "technically". I suppose we could just use old instructions, but I still want it as safe as possible. I still can't get a hold of Astria

 

[Dave48103]

FWIW I don't understand why permabase was used by the contractor under the fireplace when durock was used for the hearth. What was he thinking?

View attachment 188722

We had him tear out the permabase on the hearth and replace with durock, that was easy. But can't tear out the permabase under the unit.

 

[begreen]

Good eye, sounds like you caught the most important location.

 

[BenTN]

Isn't the unit permanently marked with all clearances to combustibles? when we installed our osburn there was a difference in the shelf measurement between docs online and manual that came with unit. the tag affixed to the fireplace states all clearances and supercedes all other documentation, per my reading.

 

[Dave48103]

Isn't the unit permanently marked with all clearances to combustibles? when we installed our osburn there was a difference in the shelf measurement between docs online and manual that came with unit. the tag affixed to the fireplace states all clearances and supercedes all other documentation, per my reading.

I thought about that, the tag does list all the clearances but does not say it needs to be on a non-combustible surface. Hmmm. Interesting thought.


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