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

[JZegowitz]

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

 

[steveray]

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

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.....

 

[Firestop Guy]

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

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.

 

[steveray]

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.

Great first post!.....Glad to have the best firestop guy I know on here now....

 

[mtlogcabin]

Welcome to the forum and thanks for the great explanation

 

[icatalyst]

What about acoustical considerations? We have had two consultants insist that making the ceiling gyp "tight" to the double top plate will short-circuit the performance of the floor-ceiling assembly with RC. Other than resorting to Merriam Webster, what does "tight" mean? Can there be a small gap - say, a quarter-inch wide - that gets filled with fire-rated acoustical caulk ... and that's "tight enough for jazz"? ;-)
Thanks in advance for any feedback!

 

[Firestop Guy]

What about acoustical considerations? We have had two consultants insist that making the ceiling gyp "tight" to the double top plate will short-circuit the performance of the floor-ceiling assembly with RC. Other than resorting to Merriam Webster, what does "tight" mean? Can there be a small gap - say, a quarter-inch wide - that gets filled with fire-rated acoustical caulk ... and that's "tight enough for jazz"? ;-)
Thanks in advance for any feedback!

Any hard connection is going to decrease the STC though 4-5 decibels is typically considered not noticeable. I don't know that gypsum tight to the top plates is going to lower the STC that much with the standard RC set ups. The IBC requires a minimum STC of 50 and there are multiple ways to achieve more than that but anything that directly counters prescriptive requirements is not allowed. In this case, the ceiling membranes being tight to the top plates is a life safety and structural safety issue which takes precedence over STC ratings. See the attached pdf for what the code requires. Mineral wool insulation is what we see used most often to ***** STC ratings. Some will use the lower density 2 pound per cubic foot (PCF) sound attenuation blankets though 4PCF has much better sound and thermal insulation properties.

There is no such thing as a "fire-rated" acoustical or firestop sealant. The sealants do not carry any rating in and of themselves. See the attached "Basic Install Guide..." for more information on that.

I have looked at STC enough to understand that a number of the noises people complain about (someone's subwoofer, a barking dog, a crying baby) are not in the range of sound frequency range measured by STC. Here is a good primer on STCs https://www.acousticalsurfaces.com/blog/acoustics-education/sound-transmission-class-stc-rating/

Hope that helps.

 

[steveray]

What about acoustical considerations? We have had two consultants insist that making the ceiling gyp "tight" to the double top plate will short-circuit the performance of the floor-ceiling assembly with RC. Other than resorting to Merriam Webster, what does "tight" mean? Can there be a small gap - say, a quarter-inch wide - that gets filled with fire-rated acoustical caulk ... and that's "tight enough for jazz"? ;-)
Thanks in advance for any feedback!

Fire>acoustic considerations.....

 

[Yankee Chronicler]

What about acoustical considerations? We have had two consultants insist that making the ceiling gyp "tight" to the double top plate will short-circuit the performance of the floor-ceiling assembly with RC. Other than resorting to Merriam Webster, what does "tight" mean? Can there be a small gap - say, a quarter-inch wide - that gets filled with fire-rated acoustical caulk ... and that's "tight enough for jazz"? ;-)
Thanks in advance for any feedback!

That would depend on the listing and manufacturer's instructions for the "caulk" (sealant). If the listing says it has been tested for gaps up to a quarter of an inch, then it's acceptable. If the listing only covers gaps no larger than 3/16 of an inch, then obviously a quarter-inch gap is not acceptable.

 

[redeyedfly]

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.

Interesting guide but whoever prepared it doesn't really understand how fire partitions are framed in the real world. Floor trusses don't run through fire barriers unless someone screwed up and then it becomes an enormous PITA to maintain continuity of the fire barrier membranes around all the truss webs. Assuming it's framed how 99.9% of fire barriers are framed, the floor/ceiling assembly stops at the fire barrier and continues again on the other side; there is no penetration of the horizontal assembly. A fire barrier is NOT a penetration of the horizontal assembly.

Also, the gap is for deflection just like you said. The interior partitions are not designed to be load bearing, the trusses don't have bearing points at the non-load bearing partitions. You allow the trusses to deflect at the partitions so they don't load walls which are not designed for it.

 

[redeyedfly]

That would depend on the listing and manufacturer's instructions for the "caulk" (sealant). If the listing says it has been tested for gaps up to a quarter of an inch, then it's acceptable. If the listing only covers gaps no larger than 3/16 of an inch, then obviously a quarter-inch gap is not acceptable.

Agreed this is the typical detail for maintaining both fire and sound.

You definitely don't get to tell the AHJ that since fire>sound, you can ignore the sound requirements. You have to figure our how to provide both with your design. The good news is that there are listed firestop systems for this joint. As you probably guessed, they consist of a non-hardening fire caulk. And yes, I know fire caulk isn't listed but it is the only element in the listed system for these conditions. 3M and Hilti both have them.

 

[Firestop Guy]

Interesting guide but whoever prepared it doesn't really understand how fire partitions are framed in the real world. Floor trusses don't run through fire barriers unless someone screwed up and then it becomes an enormous PITA to maintain continuity of the fire barrier membranes around all the truss webs. Assuming it's framed how 99.9% of fire barriers are framed, the floor/ceiling assembly stops at the fire barrier and continues again on the other side; there is no penetration of the horizontal assembly. A fire barrier is NOT a penetration of the horizontal assembly.

Also, the gap is for deflection just like you said. The interior partitions are not designed to be load bearing, the trusses don't have bearing points at the non-load bearing partitions. You allow the trusses to deflect at the partitions so they don't load walls which are not designed for it.

My bad on the diagram. I threw it together too quickly. The point of it was to show how RC is often incorrectly installed
At the same time, in Type VA, the separation walls are fire partitions, not fire barriers. Fire partitions extend from the floor membrane (sub-floor) of one horizontal floor/ceiling assembly to the underside (ceiling membrane) of the next floor/ceiling assembly. We routinely see framing running perpendicular to the unit separation walls, but the trusses above the separation wall are not through a fire-rated assembly since the fire partition stops at the ceiling level. The sealant around the truss penetrations in the photo is just a smoke seal. That project was permitted when the IBC still required draftstop for the conditions on that project. The gypsum is just draftstop, not a rated wall assembly. A point in support of that, there are not any UL Certified firestop systems for wood framing members through rated gypsum wall assemblies and there are not any UL Certified joint systems for gypsum to wood subflooring, a condition that would be common if those separation walls were fire barriers that were required by code to extend from subfloor to subfloor.
Also,
§420.2 specifically requires separation walls to be constructed as fire partitions.
§708.4.2 requires the fire partition to be secured to the underside of the floor/ceiling assembly which is at the ceiling level.
§718.2.2 requires fireblocking at the floor and ceiling level.
§714.5.2.7 loops back to the issue of STC vs code requirement by requiring the ceiling membrane to be tight to the top plates.

All that combines to establish that the separation walls are fire partitions, not fire barriers

 

[Firestop Guy]

That would depend on the listing and manufacturer's instructions for the "caulk" (sealant). If the listing says it has been tested for gaps up to a quarter of an inch, then it's acceptable. If the listing only covers gaps no larger than 3/16 of an inch, then obviously a quarter-inch gap is not acceptable.

The only UL Certified systems for any kind of "joint" in Type V-A are as the attached, and only Hilti and STI have one. Both deal with the junction of the wall gypsum to the ceiling membrane, not the ceiling membrane to the top plates since the code says it should be tight to the top plates. It does not seem to me that such a system will help with the STC, and I have never seen these systems used. I don't know that any firestop manufacturer would write an Engineering Judgment for sealant between the ceiling membrane and the top plates. They might, though I have never seen one. While we have always been delegated the responsibility to review and approve firestop system submittals on behalf of the AHJ, as a firestop inspector I would take an EJ like that to the AHJ for their approval. Most EJs do not require that I do so, and while I can understand how an EJ like that could perform fully, the §714.5.2.7 still says, "tight to the top plates" and I don't get to set that aside. If the AHJ approves it, then I can inspect for conformance to the EJ.
All the gun grade firestop materials carry an STC rating. The two materials allowed by the attached system are FS One Max with an STC of 62 and CP606 with an STC of 68.

 

[steveray]

You definitely don't get to tell the AHJ that since fire>sound, you can ignore the sound requirements.

As soon as they show me that it was tested for sound "not tight" they might be able to build it that way....Until that time, I win....

 

[redeyedfly]

My bad on the diagram. I threw it together too quickly. The point of it was to show how RC is often incorrectly installed
At the same time, in Type VA, the separation walls are fire partitions, not fire barriers. Fire partitions extend from the floor membrane (sub-floor) of one horizontal floor/ceiling assembly to the underside (ceiling membrane) of the next floor/ceiling assembly. We routinely see framing running perpendicular to the unit separation walls, but the trusses above the separation wall are not through a fire-rated assembly since the fire partition stops at the ceiling level. The sealant around the truss penetrations in the photo is just a smoke seal. That project was permitted when the IBC still required draftstop for the conditions on that project. The gypsum is just draftstop, not a rated wall assembly. A point in support of that, there are not any UL Certified firestop systems for wood framing members through rated gypsum wall assemblies and there are not any UL Certified joint systems for gypsum to wood subflooring, a condition that would be common if those separation walls were fire barriers that were required by code to extend from subfloor to subfloor.
Also,
§420.2 specifically requires separation walls to be constructed as fire partitions.
§708.4.2 requires the fire partition to be secured to the underside of the floor/ceiling assembly which is at the ceiling level.
§718.2.2 requires fireblocking at the floor and ceiling level.
§714.5.2.7 loops back to the issue of STC vs code requirement by requiring the ceiling membrane to be tight to the top plates.

All that combines to establish that the separation walls are fire partitions, not fire barriers

I didn't mention unit separation walls. Agreed they are fire partitions. Completely disagree that they are membrane penetrations.

You skipped past 708.4.2. Some version of the fireblocking/draftstopping requirement above partitions has always been in the IBC (2000-2024). A fire partition does not end at the ceiling membrane, it is required to continue up through the floor assembly space, either continuing to the underside of the deck like a fire barrier or with fireblocking/draftstopping. The unit separation wall is NOT a membrane penetration of the horizontal assembly. A fire partition or fire barrier is the perimeter of a horizontal assembly compartment. The intersection of assemblies is a joint, not a membrane penetration.

To be clear, unrated unit interior walls ARE membrane penetrations if detailed per 714.5.2-7. This post is not commenting on the fire caulk detail for sound as it relates to that code provision.

 

[steveray]

They can go to the gyp:

708.4​

Fire partitions shall extend from the top of the foundation or floor/ceiling assembly below and be securely attached to one of the following:

1. 1.The underside of the floor or roof sheathing, deck or slab above.
2. 2.The underside of a floor/ceiling or roof/ceiling assembly having a fire-resistance rating that is not less than the fire-resistance rating of the fire partition.

714.5.2
AND THEN THEY CAN PENETRATE IT:

7.The ceiling membrane of a maximum 2-hour fire-resistance-rated horizontal assembly is permitted to be interrupted with the double wood top plate of a wall assembly that is sheathed with Type X gypsum wallboard, provided that all penetrating items through the double top plates are protected in accordance with Section 714.5.1.1 or 714.5.1.2 and the ceiling membrane is tight to the top plates.

They do get out of the blocking when sprinklers are in the floor system:

708.4.2​

In combustible construction where fire partitions do not extend to the underside of the floor or roof sheathing, deck or slab above, the space above and along the line of the fire partition shall be provided with one of the following:

1. 1.Fireblocking up to the underside of the floor or roof sheathing, deck or slab above using materials complying with Section 718.2.1.
2. 2.Draftstopping up to the underside of the floor or roof sheathing, deck or slab above using materials complying with Section 718.3.1 for floors or Section 718.4.1 for attics.

Exceptions:

1. 1.Buildings equipped with an automatic sprinkler system installed throughout in accordance with Section 903.3.1.1, or in accordance with Section 903.3.1.2 provided that protection is provided in the space between the top of the fire partition and underside of the floor or roof sheathing, deck or slab above as required for systems complying with Section 903.3.1.1.