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Ceiling membrane penetration by top plates..... 714.5.2/714.5.2 '18 or '15

J

JZegowitz

GREENHORN
Joined
Apr 1, 2021
Messages
13
Location
Metro Boston
Putting together a new construction, 3 story, Type 5A, 24 unit R-2 building together. Floor ceiling assemblies to be 1 hour. Question is regarding 714.5.2, or 714.4.2 depending on '18 or '15. In the field, builders always want to run the resilient channel throughout the units prior to framing non-bearing walls. The section noted above says you're allowed to interrupt the ceiling membrane with a double top plate as long as the wall is sheathed with type 'x' gwb. Ive seen in the field where a rip of the ceiling membrane gyp is placed atop the non bearing walls THEN allowed to frame interior walls to the underside of the r.c., but I wouldve thought a properly firestopped double top plate would suffice as interrupting the membrane - does'nt (2) plates provide the required time rating as would the 5/8" X ?
Thanks,
JZ
 
JZegowitz said:
Putting together a new construction, 3 story, Type 5A, 24 unit R-2 building together. Floor ceiling assemblies to be 1 hour. Question is regarding 714.5.2, or 714.4.2 depending on '18 or '15. In the field, builders always want to run the resilient channel throughout the units prior to framing non-bearing walls. The section noted above says you're allowed to interrupt the ceiling membrane with a double top plate as long as the wall is sheathed with type 'x' gwb. Ive seen in the field where a rip of the ceiling membrane gyp is placed atop the non bearing walls THEN allowed to frame interior walls to the underside of the r.c., but I wouldve thought a properly firestopped double top plate would suffice as interrupting the membrane - does'nt (2) plates provide the required time rating as would the 5/8" X ?
Thanks,
JZ
Click to expand...
The problem is this:

The double top plate is a prescriptive penetration of a membrane of a listed assembly which typically needs a listed penetration.....When you then penetrate the plates (prescriptive rating) with pipes and wires, everything is an engineering judgment as there is no listed penetration detail for that yet as the manufacturers are too busy making money to test that.....
 
JZegowitz said:
Putting together a new construction, 3 story, Type 5A, 24 unit R-2 building together. Floor ceiling assemblies to be 1 hour. Question is regarding 714.5.2, or 714.4.2 depending on '18 or '15. In the field, builders always want to run the resilient channel throughout the units prior to framing non-bearing walls. The section noted above says you're allowed to interrupt the ceiling membrane with a double top plate as long as the wall is sheathed with type 'x' gwb. Ive seen in the field where a rip of the ceiling membrane gyp is placed atop the non bearing walls THEN allowed to frame interior walls to the underside of the r.c., but I wouldve thought a properly firestopped double top plate would suffice as interrupting the membrane - does'nt (2) plates provide the required time rating as would the 5/8" X ?
Thanks,
JZ
Click to expand...
The ripper of GWB above non-rated walls is still allowed since the GWB ceiling membrane will essentially continue across it uninterrupted. However, assuming you have a single top plate at the non-rated walls, that top plate must be tight against the GWB ripper above it. We are seeing projects with the structural engineer wants a 1/2" gap between the ripper and the single top plate for deflection. (I am not a structural engineer, so I do not understand that. If the trusses are bearing on the outer and corridor walls or on the rated demising walls, I do not understand how 1/2" gap is needed on interior walls, ah, but I digress!) You can build interior non-rated walls with a double top plate (must be sheathed with Type X) and the ceiling membrane must then be tight to the top plates. See the attached guide for more info.
 

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Firestop Guy said:
The ripper of GWB above non-rated walls is still allowed since the GWB ceiling membrane will essentially continue across it uninterrupted. However, assuming you have a single top plate at the non-rated walls, that top plate must be tight against the GWB ripper above it. We are seeing projects with the structural engineer wants a 1/2" gap between the ripper and the single top plate for deflection. (I am not a structural engineer, so I do not understand that. If the trusses are bearing on the outer and corridor walls or on the rated demising walls, I do not understand how 1/2" gap is needed on interior walls, ah, but I digress!) You can build interior non-rated walls with a double top plate (must be sheathed with Type X) and the ceiling membrane must then be tight to the top plates. See the attached guide for more info.
Click to expand...
Great first post!.....Glad to have the best firestop guy I know on here now....
 
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