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Elevator shaft construction

H

hans@dha-architects.

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Joined
Oct 12, 2022
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71
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FARMINGTON, CT
I have a three story apartment building just finishing up and the elevator company was installing the rails yesterday and they questioned the sheetrock on the interior - in lieu of using metal studs and shaftwall liner panels, we did 2x6 wall framing with two 1/2" layers type X sheetrock on the inside of shaft, 5 1/2" mineral wool insulation and 5/8" type x on the outside - the installer said that they usually see double 5/8, not 1/2"? even though the construction is a-symmetrical, it still has a one hour rating, is there something I'm overlooking here? the interior sheetrock is obviously continuous and the only penetration of the exterior layer is the subfloor, we have fire hangers for the floor joists that connect to the shaft, so essentially continuous as well
 
A quick answer until you can provided the listing number would be to note that per 2021 IBC Table 722.2.1.4(2) 722.6.2(1), a single layer of 5/8-in Type X GWB has a 40 30-minute exposure, whereas, one layer of 1/2-in Type X GWB has a 25-minute exposure or two layers of regular 1/2-in GWB has a 40-min exposure allotment.

EDIT: Thank you Steveray
 
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As long as you have a listed assemble and all listed penetrations you should be good.....you would likely need an EJ for the subfloor penetration as wood penetration details are lacking...
 
classicT said:
A quick answer until you can provided the listing number would be to note that per 2021 IBC Table 722.2.1.4(2), a single layer of 5/8-in Type X GWB has a 40-minute exposure, whereas, one layer of 1/2-in Type X GWB has a 25-minute exposure or two layers of regular 1/2-in GWB has a 40-min exposure allotment.
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unfortunately no UL assembly, but yes as you point out, the double layer of 1/2" X would add up to 50 minutes which would surpass the 5/8 on the other side - the building inspector approved this change during the permit process (there is a similar assembly with metal studs but using 1/2" all around) I'm just wondering why the installers brought it up (I wasn't there, just hearing it second hand from the super), or maybe they just typically see double 5/8, not that it's required
 

703.2.1.1Nonsymmetrical wall construction.​

Interior walls and partitions of nonsymmetrical construction shall be tested with both faces exposed to the furnace, and the assigned fire-resistance ratingshall be the shortest duration obtained from the two tests conducted in compliance with ASTM E119 or UL 263. Where evidence is furnished to show that the wall was tested with the least fire-resistant side exposed to the furnace, subject to acceptance of the building official, the wall need not be subjected to tests from the opposite side (see Section 705.5 for exterior walls).
 
classicT said:
A quick answer until you can provided the listing number would be to note that per 2021 IBC Table 722.2.1.4(2), a single layer of 5/8-in Type X GWB has a 40-minute exposure, whereas, one layer of 1/2-in Type X GWB has a 25-minute exposure or two layers of regular 1/2-in GWB has a 40-min exposure allotment.
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Except you have to use 722.6 for wood assemblies....In which case you only get 50 min. on the 5/8 side...But then you get +15 for insulation...with the right insulation...
 
the building official doesn't have any problem with the assembly, we're just wondering if state elevator inspector will question it at all or even have an issue with it. regarding nonsymmetrical construction, one would assume the 5/8 side would be the least fire resistive, thus the double 1/2 side would be acceptable
 
steveray said:
Except you have to use 722.6 for wood assemblies....In which case you only get 50 min. on the 5/8 side...
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Whoops... thank you for catching that.

1/2" GWB is good for 15-min, 1/2" Type X is 25-min, 5/8" is 40-min, and double 1/2" is 40-min.
 
classicT said:
Whoops... thank you for catching that.

1/2" GWB is good for 15-min, 1/2" Type X is 25-min, 5/8" is 40-min, and double 1/2" is 40-min.
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I notice double 1/2" increases by 10 minutes over just doubling the 15 minute rating, I wonder why they don't list double 1/2" X - would it get the same additional 10 minutes to add up to 60?
 

Not quite:​

707.7Penetrations.​

Penetrations of fire barriers shall comply with Section 714.

714.4.2Membrane penetrations.​

Membrane penetrations shall comply with Section 714.4.1.

714.4.1.2Through-penetration firestop system.​

Through penetrations shall be protected by an approved penetration firestop system installed as tested in accordance with ASTM E814 or UL 1479, with a minimum positive pressure differential of 0.01 inch (2.49 Pa) of water and shall have an F ratingof not less than the required fire-resistance rating of the wall penetrated.
 
steveray said:

Not quite:​

707.7Penetrations.​

Penetrations of fire barriers shall comply with Section 714.

714.4.2Membrane penetrations.​

Membrane penetrations shall comply with Section 714.4.1.

714.4.1.2Through-penetration firestop system.​

Through penetrations shall be protected by an approved penetration firestop system installed as tested in accordance with ASTM E814 or UL 1479, with a minimum positive pressure differential of 0.01 inch (2.49 Pa) of water and shall have an F ratingof not less than the required fire-resistance rating of the wall penetrated.
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2021 IBC ​

713.2 Construction​

Shaft enclosures shall be constructed as fire barriers in accordance with Section 707 or horizontal assemblies in accordance with Section 711, or both.

707.5 Continuity​

Fire barriers shall extend from the top of the foundation or floor/ceiling assembly below to the underside of the floor or roof sheathing, slab or deck above and shall be securely attached thereto. Such fire barriers shall be continuous through concealed space, such as the space above a suspended ceiling. Joints and voids at intersections shall comply with Sections 707.8 and 707.9
Exceptions:
  1. Shaft enclosures shall be permitted to terminate at a top enclosure complying with Section 713.12.
  2. Interior exit stairway and ramp enclosures required by Section 1023 and exit access stairway and ramp enclosures required by Section 1019 shall be permitted to terminate at a top enclosure complying with Section 713.12.
  3. An exit passageway enclosure required by Section 1024.3 that does not extend to the underside of the roof sheathing, slab or deck above shall be enclosed at the top with construction of the same fire-resistance rating as required for the exit passageway.
 
Ok...if you want to go there....Even though it is not a joint....

707.8Joints.​

Jointsmade in or between fire barriers, and jointsmade at the intersection of fire barriers with underside of a fire-resistance-rated floor or roof sheathing, slab or deck above, and the exterior vertical wall intersection shall comply with Section 715.

715.3Fire-resistance-rated assembly intersections.​

Joints installed in or between fire-resistance-rated walls, floor or floor/ceiling assemblies and roofs or roof/ceiling assemblies shall be protected by an approved fire-resistant joint system designed to resist the passage of fire for a time period not less than the required fire-resistance rating of the wall, floor or roof in or between which the system is installed.
 
steveray said:
Ok...if you want to go there....Even though it is not a joint....

707.8Joints.​

Jointsmade in or between fire barriers, and jointsmade at the intersection of fire barriers with underside of a fire-resistance-rated floor or roof sheathing, slab or deck above, and the exterior vertical wall intersection shall comply with Section 715.

715.3Fire-resistance-rated assembly intersections.​

Joints installed in or between fire-resistance-rated walls, floor or floor/ceiling assemblies and roofs or roof/ceiling assemblies shall be protected by an approved fire-resistant joint system designed to resist the passage of fire for a time period not less than the required fire-resistance rating of the wall, floor or roof in or between which the system is installed.
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I agree, from the information provided we do not know if it is a joint, wherein 715.3 would be moot.
 
steveray said:
It's a penetration of the fire rated assembly...Maybe I didn't understand your post #18?
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Without a complete plan set, it is difficult to know if the floor is a horizontal assembly. If it is, then the requirements for a joint apply and I would look for the joint detail and appropriate fire-stopping that is likely specified. But, in this case, the floor sheathing would likely be permitted to be continuous through the wall.

If the floor is not rated, then I similarly see not issue given that the fire barrier must only extend to the sheathing. By no means do I believe the GWB on the interior of the shaft can be interrupted; but I see no issue with the floor sheathing breaking the membrane on the other side. The floor sheathing is either part of a rated assembly protected by a joint, or is non-rated.
 
classicT said:
Without a complete plan set, it is difficult to know if the floor is a horizontal assembly. If it is, then the requirements for a joint apply and I would look for the joint detail and appropriate fire-stopping that is likely specified. But, in this case, the floor sheathing would likely be permitted to be continuous through the wall.

If the floor is not rated, then I similarly see not issue given that the fire barrier must only extend to the sheathing. By no means do I believe the GWB on the interior of the shaft can be interrupted; but I see no issue with the floor sheathing breaking the membrane on the other side. The floor sheathing is either part of a rated assembly protected by a joint, or is non-rated.
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I agree...and we will likely agree to disagree...
 
The contractor and installer are probably accustomed to seeing the 2-hour assembly required in a taller building.
 
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