# R602.8.1 Materials for fireblocking



## ewenme (Apr 13, 2010)

:|  Do you allow friction fiberglass batts as fireblocking per this section? Do they fulfill the requirement to be "_installed in suach a manner as to be securely retained in place_"? Or do you require solid blocking, or kraft-faced batts?


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## Mule (Apr 14, 2010)

Yes we allow friction fiberglass.


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## JayHawkInspector (Apr 14, 2010)

I think you should remove the paper before I would allow it to be used as a fireblock.


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## Yankee (Apr 16, 2010)

Yes to fiberglass insulation (minus the paper backing)


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## RJJ (Apr 16, 2010)

No Kraft faced batts. I want them secured or real tight.


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## Darren Emery (Apr 28, 2010)

Just curious - why (and per what section of the code) do you require the paper to be removed?


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## Builder Bob (Apr 28, 2010)

paper is combustible;hence kinda opposite of "fire" blocking........ Plus paper doesn't compress as easily as unkrafted rolls of fiberglass insulation. Fiberglass batting has to be compacted in order to be effective as fire stopping.


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## Mule (Apr 28, 2010)

Builder Bob said:
			
		

> paper is combustible;hence kinda opposite of "fire" blocking........ .


So is wood. But wood is allowed.


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## Yankee (Apr 29, 2010)

Darren Emery said:
			
		

> Just curious - why (and per what section of the code) do you require the paper to be removed?


If it is packed tight into a space and the kraft side is right against another material, then I guess it wouldn't matter. But the kraft facing may not be left exposed (as per instructions on the paper backing). That means exposed even within a cavity IMHO.


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## Mac (Apr 29, 2010)

If it is in a cavity then why is it exposed?


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## Yankee (Apr 29, 2010)

Mac said:
			
		

> If it is in a cavity then why is it exposed?


Its surface is exposed to the air. Installed so that another material is against (touching) the paper backing is not exposed (to an airspace).

See R302.10.1 Exception 1 (2009 IRC)


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## EPrice (Apr 29, 2010)

Darren Emery said:
			
		

> Just curious - why (and per what section of the code) do you require the paper to be removed?


In the UBC the requirement that the batts be unfaced was worded more clearly, but I think it is still there in R602.8.1.  The fact that R602.8.1.1 speaks of unfaced fiberglass implies that that is what is meant in R602.8.1.  Beyond that, R602.8.1 list the materials that are allowed.  Batts or blankets of mineral or glass fiber are listed.  Paper is not listed, therefore it is not allowed.


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## Mac (Apr 29, 2010)

Does the full depth & width cavity insulation in an exterior wall cavity count as fireblocking?

My point is that the paper doesn't matter - the code allows combustible material to be used as fireblocking. Friction-fitted insulation can come loose and sag or settle, and if concealed in an enclosed stud bay or cavity it willnot be seen, and won't perform its intended funciton. Stapled in place paper face FG has a better probability of staying put.


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## brudgers (Apr 29, 2010)

EPrice said:
			
		

> In the UBC the requirement that the batts be unfaced was worded more clearly, but I think it is still there in R602.8.1.  The fact that R602.8.1.1 speaks of unfaced fiberglass implies that that is what is meant in R602.8.1.  Beyond that, R602.8.1 list the materials that are allowed.  Batts or blankets of mineral or glass fiber are listed.  Paper is not listed, therefore it is not allowed.


Do you require the removal of paper from gypsum board when used as fire blocking too?


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## High Desert (Apr 29, 2010)

The paper faced insulations does not meet flame spread requirements if left exposed. If it's exposed, then it has to be removed. If not exposed, leave it on.


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## Yankee (Apr 29, 2010)

Mac said:
			
		

> Does the full depth & width cavity insulation in an exterior wall cavity count as fireblocking? My point is that the paper doesn't matter - the code allows combustible material to be used as fireblocking. Friction-fitted insulation can come loose and sag or settle, and if concealed in an enclosed stud bay or cavity it willnot be seen, and won't perform its intended funciton. Stapled in place paper face FG has a better probability of staying put.


The paper used to stable it up with will be the first to go, then the batt better be stable on its ownh


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## ewenme (Apr 29, 2010)

Mac:  That was my original question: does the batt fulfill the requirement to 'be securely retained in place?'  Two of my inspector disagree.  When I read the code section, I say it does fulfill the requirement. Not that I like it. Always in the past I'd required solid blocking for fire blocking.  If the requirement is to prevent a chimney effect in the stud bay, then I think the FG batts would do it.

Thanks everyone for the comments and discussion. I found the faced/un-faced batt discussion particularly interesting. I still think that if FG batts suffice, then Kraft-face would also suffice. The backing of the gypsum board is paper too!


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## Darren Emery (Apr 29, 2010)

Thanks for the replies, all.  I have allowed paper faced batts as fireblock, but I sure didn't like it.  I just don't think the code is clear enough, either way.


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## Mule (Apr 29, 2010)

Okay, I'm thinking here.....scary but true!

Okay...there's a flame inside a wall or whatever...If the paper on the insulation is facing the flame, the paper burns off and you still have the insulation left as a fireblock.

Okay...there's a flame inside a wall or whatever...If the paper on the insulation is where the flame cannot get to the paper, it doesn't burn because there is fireblocking.

The code allows wood, plywood, gypsum, particleboard and these are all combustionable materials.

R602.8.1 Materials. includes mineral or glass fiber as allowable material for fireblocking.

Then a little farther along in the code there is a specific section for unfaced fiberglass batt insulation.

R602.8.1.1 Unfaced fiberglass. Unfaced fiberglass batt

insulation used as fireblocking shall fill the entire cross

section of the wall cavity to a minimum height of 16

inches (406 mm) measured vertically. When piping, conduit

or similar obstructions are encountered, the insulation

shall be packed tightly around the obstruction.

In my opinion paper on insulation is okay for fireblocking.


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## GHRoberts (Apr 29, 2010)

I think the paper is removed to prevent the paper side from forming a chimney up the wall. There is not enough combustible  paper there to matter in a fire.


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## Glennman CBO (Apr 30, 2010)

If you read the words printed on the paper that is backing the insulation, it will state that it is not just flamable, but it's highly flamable, and that it must be covered with an approved building material. If the paper will be in full contact with the inside of the drywall, then it is fine. However, if the paper will be left exposed in the cavity, it must be removed.

I have yet to see a kraft faced paper that doesn't have these words on it. I even ran across some a while back at a remodel that was of the foil covered paper type that said the same thing on it. Check with the manufacturer.


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## peach (May 2, 2010)

paper is more combustible than wood.. once the kraft paper burns away, there in nothing to hold the fiberglass in place.  Require something else


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