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  • 1.  Type V: When a fire-rated wall meets fire-rated floor, and vice versa

    Posted 08-24-2020 06:20 PM
    How do I find a set of details (preferably UL listed or ESR rated, if possible) that solve the intersection between a 1-hour rated wall and a 1-hour rated floor assembly, in Type V construction? 

    I'm working on a couple of residential duplexes. In each duplex, I have two units that start out side by side on the ground level, then on the second floor, one of the units goes over part of the other unit. The plan checker is insisting that a rated wall cannot end at a rated floor (as in a T-intersection, if viewed in section), that a rated floor cannot end at a rated wall (as a T-intersection if viewed in section), and that a rated wall and rated floor cannot form an L-intersection (if viewed in section). The plan checker says the 1-hour separation wall must extend from foundation to roof. Previous similar projects were permitted, so now I am confused. Have I learned this incorrectly?

    Thanks in advance for your advice and guidance!


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    Sandy Liu AIA
    Pasadena CA
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  • 2.  RE: Type V: When a fire-rated wall meets fire-rated floor, and vice versa

    Posted 08-25-2020 08:47 PM
    Residential townhouse separation does want to continue all the way up, on commercial projects where there is an obstruction I have used a horizontal wall offset such as shaftwall.

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    Herman Coronado AIA
    Partner
    Curry Boudreaux Architects
    Houston TX
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  • 3.  RE: Type V: When a fire-rated wall meets fire-rated floor, and vice versa

    Posted 08-26-2020 09:05 AM
    Townhouses yes, but this question is regarding a duplex. Townhouses have a property line, on the ground, that must be respected from ground to roof.  I own a townhouse that is by all appearances a duplex, but the legal status is a townhouse (or in some jurisdictions "zero lot line).

    So that is the first question; is it truly a duplex (2 family residence on a single lot) by definition?  If it is not, the separation needs to follow the lot line.

    If it is a duplex the separation should be permitted to zig-zag from the ground to the roof as long as each unit is properly separated. The details are available.

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    Mark Smith AIA, LEED AP
    Sr Architect
    CEMS Engineering, Inc.
    Winnabow NC
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  • 4.  RE: Type V: When a fire-rated wall meets fire-rated floor, and vice versa

    Posted 08-25-2020 09:11 PM
    My first thought is to contact USG to see if they have an approved detail that you can use.

    AHJ is right in that the code does talk about the wall going from the foundation to/through the roof. Contact the code writers (ICC?) and ask them for an interpretation.

    JIM GALLAGHER, AIA, CBO




  • 5.  RE: Type V: When a fire-rated wall meets fire-rated floor, and vice versa

    Posted 08-26-2020 02:03 PM
    Sandy:

    First of all what kind of wall are we talking about, Fire Wall, Section 706 or Fire Partition, Section 708?  This will make a difference on what needs to complied with. If it is a Fire Wall, then structural stability and vertical continuity are very important (foundation to roof). If it is a Fire Partition, separation between dwelling units within a single building, there is difference in what is required.

    As for details, UL listed assemblies are very specific and mainly address a single component: Wall, Floor, Roof, etc. Very few assemblies are tested as a group, floor to wall. There are too many possibilities to test. Testing is very expensive. There a lot suggested details, but the general rule is meeting what the code is looking for for the type of assembly. Assembly intersections are the hardest to comply with because there are little off the shelf listed assemblies to use. 

    Determine the wall type, establish what the code wants and work with the AHJ on the detail required to comply. When in doubt, block the heck out of it.

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    Kerwin Lee AIA
    Lafayette CA
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  • 6.  RE: Type V: When a fire-rated wall meets fire-rated floor, and vice versa

    Posted 08-26-2020 03:55 PM
    Are you building under jurisdiction of the IBC or the IRC? 

    If under the IBC, dwelling unit separations are most likely allowed to be fire partitions or fire barriers, or unlikely even a fire wall.  A fire wall must extend from the ground to the roof without horizontal offsets.  Fire partitions and fire barriers are permitted to offset or terminate at horizontal floor/ceiling assemblies.  

    I am not fully familiar with IRC requirements, but seem to recall that maybe it does require unit separations to extend from ground to roof without offsets.  

    You will need to clarify which Code jurisdiction you are designing under to determine how you can proceed.

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    Craig Hess AIA
    Woodbury MN
    [Minneapolis]
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  • 7.  RE: Type V: When a fire-rated wall meets fire-rated floor, and vice versa

    Posted 08-26-2020 06:23 PM
    It depends on the fire-rated assembly and the required rating. So I'll address those first and then your specific situation.

    Fire walls are required to extend from the foundation through the roof. A fire wall may stop at the underside of the roof deck/sheathing under specific situations.

    Fire barriers must extend from the top of the foundation or floor/ceiling assembly to the underside of the floor or roof sheathing. They must be continuous through concealed spaces.

    Fire partitions must extend from the top of the foundation or floor/ceiling assembly to (1) the floor or roof deck or sheathing above, or (2) to the underside of the floor/ceiling or roof/ceiling that has a rating not less than that of the fire partition.

    Rated floor and roof assemblies must comply with the requirements for horizontal assemblies. No vertical openings are permitted except where allowed by the code. They must be continuous, but there are no restrictions on terminating a horizontal assembly at a wall having a fire-resistance rating equal to or greater than the horizontal assembly.

    In your situation, the separation required is a dwelling unit separation per Section 420 of the IBC. Fire partitions and horizontal assemblies are required to have no more than a 1-hour rating. In your case, a 1/2-hour rating is all that is required since it is Type VB construction. As mentioned above for fire partitions, the wall can stop at a floor/ceiling assembly of equal or greater rating. Thus, if the floor/ceiling assembly is also 1/2-hour-rated, then the fire partition can stop at the 1/2-hour-rated floor/ceiling assembly.

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    Ronald Geren AIA, CSI, CCS, CCCA
    Principal
    RLGA Technical Services
    Scottsdale AZ
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  • 8.  RE: Type V: When a fire-rated wall meets fire-rated floor, and vice versa

    Posted 08-26-2020 06:50 PM
    Good Afternoon Sandy,

    The building code information you provide is a bit confusing.  That may be a large part of the miscommunication with the plan reviewer.  In order to answer your question(s), I will have to make a few assumptions.  From what you have described it is not clear if you are designing to meet the IRC or the IBC design requirements.  This is your choice and it must be stated on the permit application in order for the plan reviewer to know what you want.  This is particularly true if you want the residential building to be reviewed under the IBC requirements (which is what it sounds like you desire to do).  I will use the 2018 IBC for all references.

    From the words you have used in your question, I will assume that when you describe the building as a duplex we are talking about a single property (lot) with one building on it and that building will contain two dwelling units which must be properly separated from each other.  The Occupancy Type of the building will be R-3 and the Construction Type will be VB (fully fire sprinklered).

    With the aforementioned parameters, Section 420.2 and 420.3 will require the two dwelling units in the building to be separated by "Fire Partitions" (walls) designed to meet the requirements of Section 708 and, in your case, a Horizontal floor/ceiling assembly designed to meet Section 711.  For both the wall and floor assemblies, the fire rating must be a minimum of 1/2 hour.  The fire rated partition(s) must meet the requirements of Section 708.4 (using both of the two conditions stated).  The rated wall(s) can be offset as long as they begin and terminate at rated horizontal assemblies as required in 708.4.

    The vertical fire partition can bear on a slab on grade, the top of the foundation wall, or it can bear on the top of a fire rated floor assembly.  The separation just has to be continuous (the wall can be offset). I would suggest you keep the rated assemblies simple and select approved assemblies from Tables 721.1(2) and 721.1(3).  These are just as acceptable as using a UL or other tested assemblies.

    The detailing of both the wall(s) and the floor assemblies must each maintain continuous rated assemblies.  The rated floor assemblies must be rated for the entire span.  The supporting walls will most likely not be required to be rated assemblies.

    What you want to do is allowed.  You just need to guide the plan reviewer to the exact thing you want to do.







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    Bruce Fischer AIA
    Associate Professor
    University of Nebraska, Lincoln
    Lincoln NE
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  • 9.  RE: Type V: When a fire-rated wall meets fire-rated floor, and vice versa

    Posted 08-27-2020 08:21 AM

    Dear Sandy:

     

    For buildings constructed in accordance with the International Building Code please see IBC-2018 Section 714.5.2, subpart "7".

    For dwellings constructed in accordance with the International Residential Code please see IRC-2018 Section R302.3.

     

    Please note that since 2012 the IBC and IRC have seen modifications to these sections and therefore not knowing what the jurisdiction in question has adopted (e.g. which I-code used as a benchmark for adoption) I would suggest looking at the similar provisions in those edition documents.

     

    You may also wish to contact such entities as National Gypsum Company, PABCO Gypsum, CertainTeed Gypsum, American Gypsum Co., Georgia Pacific, USG, HILTI, 3M and the like to see what individual fire endurance tested designs they may have for your application.

     

    Jonathan Humble, FAIA, NCARB, LEED BD+C