Tagged With "Design U360"

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Fire Resistance Rating of a proposed design

John O ·
We are proposing to install a "fire barrier" wall that we believe will qualify for at least a 2-hour fire resistance rating. The existing building has a partial wall in place which has 5" steel poles supporting the structure above. It is essentially two of a 2" x 4" wood stud, 24 in. centers, wall, set back-to-back, so there are 4 layers of 5/8" Type X gypsum in total. Studs are staggered 12", and drywall installed vertically so that all seams are supported. The 5" poles are integrated, and...
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Re: Fire Resistance Rating of a proposed design

John O ·
Thank you for your expertise, time and suggestions. I have seen the WP 3820 generic system you referenced. If only the facing surface helps, I don't know why the 1" gap in the middle is relevant. It would seem the gap could be replaced with anything, or eliminated. Does pretty much any solution with double 5/8" on the exterior qualify as 2hr, but not much else? I don't understand how U360 rates as 2hr. Can you explain that? See the additional attachment. Thanks again.
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Re: Fire Resistance Rating of a proposed design

rlga_AZ ·
Only if you can prove it via testing. Otherwise, use a system that is prescriptively approved by the code (UL, GA-600, IBC Table 721.1(2), or the calculated method). However, the calculated method for wood frame construction is limited to 1-hour assemblies. Two layers of 5/8-inch Type X gypsum board will generally provide the 2-hour fire resistance. UL Assembly U360 would probably work if the steel columns did not interrupt the center membrane--they are great thermal conductors, which is not...
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Re: Fire Resistance Rating of a proposed design

rlga_AZ ·
Fire resistance in a wall assembly is a two-way system. Only the membrane facing the fire exposure and its supporting structure are effective in providing fire resistance--the membrane on the opposite side has very little to no affect on the overall fire resistance of an assembly. Therefore, you only have 2 layers of gypsum board, plus the framing, providing fire resistance. With a double framed wall, the insulation only helps the side in which it is installed; thus, you have a...
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Re: Fire Resistance Rating of a proposed design

John O ·
Based on your comments, I would like to ask for your feedback on an updated version of my original design. See the attached diagram. The gypsum in the center has been moved to the outside layer, and Instead of leaving a 1" inch air gap in the middle, it has an 1/8" Hardboard Tempered Panel (something cheap) there. Something to help constrain bats of insulation. And to divide the two sections of the wall. Is this likely to be approved for a 2hr fire resistance rating? thanks!
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Re: Fire Resistance Rating of a proposed design

John O ·
Thank you again for the expert feedback. The irony of this situation is that the building code doesn't require a 2-hour rating between occupancies like F-1 and B (our situation). It is NFPA. If NFPA is the source of the requirement, then does the limit of 1-hour calculated assemblies apply? Also, in 703.3 "Alternative methods for determining fire resistance", it offers the approach of "Engineering analysis based on a comparison of building element, component or assemblies designs having...
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Re: Fire Resistance Rating of a proposed design

John O ·
Hi, we have a meeting with our local building official on Monday AM. We have decided to propose a variant on the WP 3820 that you directed us to. Instead of the 1" gap in the generic design, we are substituting a 3/8" layer of gypsum and no gap. Keeping the mineral insulation in place will be impractical without it. Thanks again for your help.
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Re: Fire Resistance Rating of a proposed design

rlga_AZ ·
John O., regarding your 9/23/16 10:50 PM post, it depends on who's enforcing the NFPA code or standard (which I assume is the NFPA 101, since you don't mention a specific code or standard). If the building department enforces the IBC (or an adopted version of it), then they'll review the project under that code and only under that code. If they also adopted the NFPA code/standard, then they'll review the project using both codes. If the former situation is true, then they probably will not...
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Re: Fire Resistance Rating of a proposed design

John O ·
Hi, We had a "preliminary review" chat with the building official yesterday. We did not get into the details of what we are proposing, but got a read on how our proposal would be evaluated. My observations: - They intend to apply IBC critieria only, as you suggested they would. The official seems to be unaware of the differences in NFPA 101 regarding separation ratings for specific occupancies. I don't think he cares. - He will evaluate our proposed design in comparison to other approved...
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Re: Fire Resistance Rating of a proposed design

John O ·
Hi, Sorry for the delay in the postmortem. I'm pleased to say that the design we proposed was accepted for a 2-hour rating. I'm attaching the explanation of the design logic that we submitted with the architectural drawings. In a nutshell, we argued that the only meaningful commonality among all 2-hour rated walls is a double layer of 5/8" type X drywall. All other variants in wall configuration don't seem to be highly relevant. Thanks again.
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