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Continuous Insulation and fire tested assemblies

erinrcollins

Hi all, I am having a hard time incorporating the continuous insulation requirement with wood frame R-2 construction. I cannot find any tested assembly that can achieve a 1 hour exterior bearing wall rating, using, from interior to exterior, 5/8" Gyp, 2x studs with kraft faced fiberglass batt insulation, wood structural sheathing, weather barriers, 1" rigid insulation, and then cladding materials (in this case masonry cavity wall, hardcoat stucco or Hardi-panels). Closest I have found is U356, but that does not include the rigid insulation. This is in Climate Zone 5 so a vapor retarder is required, and Type 5A construction requires 1 hour exterior walls since building is within 30' from neighboring structures. I can be a little flexible with materials, for example mineral wool or fire retardant treated wood, but I am still having trouble finding a suitable tested assembly. I dont really want to change to Densglass (or similar). Has anyone found a tested rated assembly using wood studs, wood sheathing, and continuous exterior insulation panels? Thanks, any information would be very appreciated.

 
Mar 5, 20 12:34 am
erinrcollins

Edit - and the wall has to be rated from both sides, due to proximity to neighboring structures.  I really cannot find an assembly that fits the bill on this one!

Mar 5, 20 1:32 am  · 
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archanonymous

Just dealt with this on a 2 hour wood frame exterior wall using up u301 ( I think - I'm on the bus so I don't have my last projects code research in front of me). Our code consultant as well as building official and permit reviewer all agreed that adding plywood sheathing, non-combustible exterior CI and non-combustible finishes were all permitted in the UL or GA design guides. Go read the notes and allowed substitutions. It's a little grey but not really.

Mar 5, 20 7:52 am  · 
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Non Sequitur

oye... just basically answered the same thing you did. oops

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archanonymous

Then we must be right!

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erinrcollins

Ah--- I read the UL intro which was unclear, but have not read GA. I'll do that.... But, found that IBC allows incorporation of additional materials as long as they are non combustible. Thanks!

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Non Sequitur

I've had no problems doing this type of wall.  I typically use a normal 1hr UL (ULC in my case) that allows substitution of the exterior layer of sheathing for either glassmat or cement board.  The rating is through this wall only, not through the cladding and CI so as lon as those 2 are non-combustible (masonry + mineral wool for example), this should work as long as you are comfortable explaining the substitutions.

Mar 5, 20 8:30 am  · 
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Chad Miller

One thing to remember is that UL listings from Canada are not accepted in America because America's UL testing procedure has a 'hose test' done at the end to ensure the assembly stays in place, Canada dose not have this. I believe (NS correct me if I'm wrong) that UL listings from America are accepted in Canada.

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Non Sequitur

We have hose tests too. Just not common.

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Chad Miller

Regardless, the Canadian UL assemblies are not accepted in America.

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Almosthip7

Its been my experience that american UL are not accepted in my jurisdiction, ULC oknly

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Non Sequitur

ULc are American details acceptable in Canada. ULC is Canada only.

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Dank Gehry

ho's test

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erinrcollins

Thanks!  Much appreciated input!  I found that the beginning of the UL book does not clearly describe what substitutions are allowed, however, this morning I found that the IBC clearly indicates that you are allowed to add materials to assemblies as long as the materials are flame/smoke/fire resistant (basically non-combustible and therefore will not decrease the overall rating).  I actually did find an assembly, though, that was approved this past February (2020)--- UL V314, and I will add rigid board mineral wool for the continuous insulation.  That takes care of the 1 hour wall.... now need to find a 2 hour steel stud assembly rated from both sides (should be more straight-forward).  Messing around with fire ratings makes me nervous. 

Mar 5, 20 9:33 pm  · 
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archanonymous

Most jurisdictions also allow calculated fire resistance... it varies by stud type and building construction, but usually 60 or 90 minute for wood is allowed.

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ngoodenow

Where in the IBC does it indicate you're allowed to add materials to assemblies? The closest thing I found is 721.1 "Where materials that change the capacity for heat dissipation are incorporated into a fire-resistance-rated assembly, fire test results or other substantiating data shall be made available to the building official to show that the required fire-resistance-rating time period is not reduced." Thanks

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senjohnblutarsky

Find an assembly you like and contact the gypsum manufacturer to get an "engineering judgement".  Most building officials will accept such things.

I've been having to do this since membrane penetrations were incorporated into the codes.  Building officials stopped taking through-penetrations.  But, no enough membrane penetrations existed.  So, I had to get an engineering judgement based on a modification of an existing through-penetration. 

Mar 9, 20 7:33 am  · 
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apscoradiales

erinrcollins,

I have come across many similar situations over years, and this is what always worked for me.

I would choose a tested assembly either from ULC (since I'm in Canada) or from ULI or from Warnock Hersey. Canadian authorities used to accept ULI assemblies without any reservations - sometimes one would have to engage in a "discussion" for them to accept Warnock Hersey, which they eventually would.

Then, I would add any material the design called for on top of the tested assembly, and that was it. Sometimes, I would contact the Building Department to "fly" this by them, and they would always give us a green light.

In your case, I would simply build a stud wall with mineral fibre insulation between the studs, together with vapour barrier, and air barrier, and use two layers of 5/8" fire rated gypsum wall board - Type X or Firecode C -  (or 1/2" cement board) on either side of the stud (for a total of 4 layers), THEN I would add all the cladding and cosmetic stuff to the wall. Fly it by the Building Department, and I'm sure they'll approve it.

I don't have my ULI, nor ULC books handy, but I'm pretty sure there is a 2 hour fire rated wood stud (either bearing or non-bearing) wall in the ULI book.

Oct 27, 20 2:02 pm  · 
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apscoradiales

ngoodenow,

I have never seen this in any code where it says you are allowed to add stuff to the rated wall assembly, but building departs will normally accept it.

Think about it; you're building an exterior gwb rated wall...you can't just leave it exposed - you have to cover it up with something or otherwise it will turn into mush when it gets rained on.

Even for interior rated walls, it's OK to add stuff - like paint or wall paper or wood or glass or whatever. Nobody is going to force you to leave a gwb wall exposed. As long as the smoke and flame spread ratings are within the code, you are fine to add material(s).

Oct 27, 20 2:16 pm  · 
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apscoradiales

erinrcollins,

"Messing around with fire ratings makes me nervous."

It shouldn't; that;s what the ULI or ULC is all about.

Now that I think about it, we used the ULC assemblies (Canadian) down in Fort Myers once. The local Building Department approved it without any reservations. But, other jurisdictions are probably reluctant to accept the ULC. That's why it's always best to talk to the authorities first or have a Code Report done by your Code Consultant who can argue on your behalf.

Oct 27, 20 2:23 pm  · 
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apscoradiales

"...Almosthip7

Its been my experience that american UL are not accepted in my jurisdiction, ULC oknly..."

Really?! Are you in Quebec - the fuckers probably wanted it in french too!

Seriously, your Building Department guys need to get educated.

Oct 27, 20 2:29 pm  · 
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Non Sequitur

this is an old discussion, but pretty I've explained this more than once before in the forum. Most UL products are acceptable but just having the UL stamp does not mean it automatically is.

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