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Thread: Firewall

  1. #1
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    Default Firewall

    Hello,

    Did an inspection today of a single story duplex. Got into the attic and noticed that there was 5/8 inch Fire rated sheet rock between the units but not 4' feet in, on the roof joists. These units are 20 plus years old and have been renovated for resale. Isn't this necessary?

    Jim

    Antebellum Inspection

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  2. #2
    Larry Wallace's Avatar
    Larry Wallace Guest

    Default Re: Firewall

    No Jim, I went thru the same thing a few months ago and two different local code guys said that the 4 ft requirement for the roof sheathing is only for mutltiple unit buildings. It is not a requirement for a duplex. No, they couldn't explain why there is a difference, just that there is a difference in the way the code is written for each case. Hope this helps.


  3. #3
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    Default Re: Firewall

    The 2003 and 2006 IRC do treat two family dwellings differently from "townhouses". Here's 2003 IRC R317.1 and R317.1.1, Two-family dwellings:

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  4. #4
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    Default Re: Firewall

    2006 IRC: SECTION R317
    DWELLING UNIT SEPARATION
    R317.1 Two-family dwellings; Dwelling units in two-family dwellings shall be separated from each other by wall and/or Floor assemblies having not less than a1-hourfire-resistance Rating when tested in accordance with ASTME119. Fire-resistance-rated floor-ceiling and wall assemblies shall extend to And be tight against the exterior wall, and wall assemblies shall extend to the underside of the roof sheathing.
    Exceptions:
    1. A fire-resistance rating of Hours hall be permitted In buildings equipped throughout with an automatic Sprinkler system installed in accordance with NFPA 13.
    2.Wall assemblies need not extend through attics paces When the ceiling is protected by not less than 5/8-inch (15.9mm) TypeX gypsum board and an attic draft Stop constructed as specified in SectionR502.12.1 is Provided above and along the wall assembly separating the dwellings. The structural framing supporting the ceiling shall also be protected by not less than -inch (12.7 mm) gypsum board or equivalent.

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    Jerry McCarthy
    Building Code/ Construction Consultant

  5. #5
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    Default Re: Firewall

    Jim,

    Yes and no. (How is that for an answer?)

    No, the IRC does not require protection of the roof sheathing for a two-family dwelling.

    Yes, fire is illiterate and cannot read deeds to see if the structure is a "townhouse" or a "two-family dwelling".

    Jerry Mc.,

    You've confused me with that drawing by not stating what it is intended to represent????

    Jerry Peck, Construction / Litigation Consultant
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  6. #6
    daniel nantell's Avatar
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    Default Re: Firewall

    how do you know the different between fire rated drywall and regular drywall .


  7. #7
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    Default Re: Firewall

    daniel,
    the drywall is required to have an identifying mark installed at the time it is made. it will say "type x","firecode",or "fire resistance",etc. once it is finished it is impossible to tell.


  8. #8
    Gregory S. Finkel's Avatar
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    Default Re: Firewall

    Jim
    Years ago fire proof plywood roof sheathing was used where the units joined. You didn't say how old the units were. They found that the fire proofing of the plywood caused delamination in the sheets and subsequently stopped using it.

    Gregg


  9. #9
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    Default Re: Firewall

    Quote Originally Posted by Gregory S. Finkel View Post
    They found that the fire proofing of the plywood caused delamination in the sheets and subsequently stopped using it.
    Gregg,

    They still make fire retardant treated plywood, they just use a different chemical now.

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  10. #10
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    Default Re: Firewall

    Greg
    "Fireproof?"
    Let's go with Jerry P's "fire resistant" please!

    Jerry McCarthy
    Building Code/ Construction Consultant

  11. #11
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    Default Re: Firewall

    Funny thing about how everyone is more concerned about the wall assembly then the drafting problem from one unit to the next.
    A year ago or so we had a multi unit complex burn to the ground that had fire rated walls and sheathing. The flames where drafting through the perforated soffit panels. Because of this officials where quick to jump in and mandate 4' solid soffit panels on shared walls sections.

    I inspected a town home 2 weeks ago and the units are brand new and vacant. The panels where not solid and I asked the "supra" all of about 22 years of age what the deal was. He said the permit was pulled right before the change and they did not have to abide by the new change. He said the AHJ also said something about it but he could not press it. I wanted to smack the lad upside the head for they willing known about the change and didn't not care about the welfare of there buyers.

    Mike Schulz License 393
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  12. #12
    Hank Hendrix's Avatar
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    Default Re: Firewall

    Looked at this 4 unit townhouse today. It may be difficult to see in the picture, but the drywall acting as a fire break is installed between the rafters against the roof decking. A 2x2 strip is nailed against the rafter to hold the drywall in place. I called it out because the rafter and 2x2 are still exposed -- am I right or wrong?
    You might also see (or not see) the missing collar ties in this area.

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  13. #13
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    Default Re: Firewall

    Quote Originally Posted by Hank Hendrix View Post
    am I right or wrong?
    Both.



    First, though, the gypsum board does not cover 4 feet of the sheathing.

    Now ...

    You are "right" in that the drywall wall is improperly installed.

    You are "wrong" about what is wrong with it.

    The drywall is just being held (I am presuming anyway) up against the roof sheathing by 'friction'. The drywall should have been nailed or screwed up in place.

    The easy way to do this is (obviously, but why it is seldom done is beyond me) to fasten the gypsum board up to the underside of the rafters, covering to one rafter (or truss) beyond the required 4 feet.

    Another way would be to install those 2x2s up next to the roof sheathing and attach them to the rafters, then fastening the gypsum board up to those 2x2s with drywall screws or nails.

    Leaving the wood exposed? That's okay, as long as it at least a 2x in size (1-1/2" thick) as it is no different than leaving the rafters (or trusses) exposed between the gypsum board.

    Now, to your missing collar ties ...

    That looks like it might be (*might* be) a structural ridge, in which case no collar ties are needed (I think, hmmm ... ??). *IF* that is not a structural ridge, the rafters are not "opposite each other". One side looks 24" centers and the other side looks 16" centers.

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  14. #14
    David Block's Avatar
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    Default Re: Firewall

    I run across a lot of units in which the drywall in the attic space is not taped or mudded at the joints. I constantly complain to the builders but they keep insisting that is meets code requirments. Am I off base on this one?


  15. #15
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    Default Re: Firewall

    Quote Originally Posted by David Block View Post
    Am I off base on this one?
    Nope.

    Jerry Peck, Construction / Litigation Consultant
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  16. #16
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    Default Re: Firewall

    david and jerry,
    i beg to differ, 2006 ibc section 2508.4 exc joint and fastener treatment need not be provided where any of the following conditions occur:
    2. on single layer systems where joints occur over wood framing members


  17. #17
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    Default Re: Firewall

    Brian
    I suspect they're referring to the horizontal joints?

    Jerry McCarthy
    Building Code/ Construction Consultant

  18. #18
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    Default Re: Firewall

    jerry,
    you're wrong! drywall applied with long dimension landing on studs and short dimension on plates does not require treatment. been in the ubc forever. i thought you taught this stuff?


  19. #19
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    Default Re: Firewall

    Brian
    Your right IF applied in the vertical direction and IF the wall height is less than 8 or 12 feet. I've spent 57 years in construction, 14 in a classroom teaching and yet would never - ever presume to know it all.

    Jerry McCarthy
    Building Code/ Construction Consultant

  20. #20
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    Default Re: Firewall

    Quote Originally Posted by brian schmitt View Post
    david and jerry,
    i beg to differ, 2006 ibc section 2508.4 exc joint and fastener treatment need not be provided where any of the following conditions occur:
    2. on single layer systems where joints occur over wood framing members

    I see I am wrong AGAIN ... mostly ... partially ... whatever ...

    ... as long as "where joints occur over wood framing" and in that photo Hank posted they SOME certainly do occur over WOOD framing ... *on that wall* ... but not *all* of the joints occur over WOOD framing

    The gypsum board on the ceiling in that photo, and as is typical, *DO NOT* occur "over wood framing" and thus would need to be mudded and taped.

    Thus, your answer is not as all encompassing as it may seem.

    Jerry Peck, Construction / Litigation Consultant
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  21. #21
    David Block's Avatar
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    Default Re: Firewall

    I have a question I need anyones educated opinion on. Recently inspected a townhome. The units were not the same height and this was a middle unit. The attic space was about 5' tall. There was drywall installed on the walls but the drywall did not extend to the roof deck. The walls in the adjacent units were bedroom walls and not attic spaces as those units were taller. I could see the drywall of the bedrooms in the adjacent units. What is the appropriate wall treatment for this units attic space?


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