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1hr party wall assembly with no airgap and staggered studs?

Idrew

Idrew

REGISTERED
Joined
Mar 10, 2023
Messages
5
Location
Frisco texas
Good Day, I am working on drawings for a remodel and am having a hard time finding an assembly to use for a part wall between units. As constructed, there is no air gap between the walls, and I am curious if just adding the 5/8 gyp sheeting makes this a one-hour wall. Typically, the assemblies we use in MFamily have an air gap. U341 says there is no minimal air gap, but the studs are not staggered. I'd like to steer the GC on this one in the right direction, I need help getting there first.

this wall.png
 

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I recommend getting this design manual, for $100 you get:

"The 2021 edition contains nearly 800 fire- and sound-rated systems for:
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redeyedfly said:
Doesn't meet 50 STC for sound.

OP - How are you designing MF (for a fee!) with no understanding of how listed wall assemblies work or that sound is the controlling issue in unit separation walls? You probably need 2 layers of gyp on one side or resilient channel to get the required STC.
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I will admit I am not 100% familiar with all of the wall assemblies there are, I doubt anyone is. I understand the wall assemblies that the company I work for, typically uses. This is a situation a little bit out of the normal, being a renovation and not a ground up. I have checked with more experienced staff and they were unable to give a definite answer, so I thought I'd ask here.
 
Idrew said:
I will admit I am not 100% familiar with all of the wall assemblies there are, I doubt anyone is. I understand the wall assemblies that the company I work for, typically uses. This is a situation a little bit out of the normal, being a renovation and not a ground up. I have checked with more experienced staff and they were unable to give a definite answer, so I thought I'd ask here.
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If you are still working on the drawings, how did those walls get built?

The assembly Joe B. found gives you the rating, but it calls for horizontal blocking (bracing) at mid-height. So add the blocking, apply 5/8" firecode sheetrock, and you're done.
 
Yankee Chronicler said:
If you are still working on the drawings, how did those walls get built?

The assembly Joe B. found gives you the rating, but it calls for horizontal blocking (bracing) at mid-height. So add the blocking, apply 5/8" firecode sheetrock, and you're done.
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Thanks,

Well, a client that we have drawn a ground up project for, had some fire damage to an apartment complex he manages/owns. He hired a general contractor to rebuild the units. They removed all the damaged dry wall, studs, building envelope and studs and started to replace them. When they got to the roof the city caught wind and stopped them and said they need to get some plans submitted. Owner turns to the company and because I worked on the ground up deal, I get assigned this project.
 
Yankee Chronicler said:
If you are still working on the drawings, how did those walls get built?

The assembly Joe B. found gives you the rating, but it calls for horizontal blocking (bracing) at mid-height. So add the blocking, apply 5/8" firecode sheetrock, and you're done.
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Dude! He provided a 44 STC assembly. That doesn't meet code for sound; minimum is 50 STC.
 
redeyedfly said:
Dude! He provided a 44 STC assembly. That doesn't meet code for sound; minimum is 50 STC.
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Dude! Did you just see his last post, it is a fire repair, at the time it was built it probably didn't require an STC of 50.

You are a Troll.
 
Idrew said:
Thanks,

Well, a client that we have drawn a ground up project for, had some fire damage to an apartment complex he manages/owns. He hired a general contractor to rebuild the units. They removed all the damaged dry wall, studs, building envelope and studs and started to replace them. When they got to the roof the city caught wind and stopped them and said they need to get some plans submitted. Owner turns to the company and because I worked on the ground up deal, I get assigned this project.
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Ah. So it's a repair. So you should be starting in the IEBC and looking under repairs. Are you under the Texas Building Code, or are you under one of the city building codes? Maybe it doesn't matter -- it appears they have all adopted the 2021 IEBC.

The Texas IEBC says this:

[BS] 405.2.1 Repairs for Less Than Substantial Structural Damage. Unless otherwise required by this section, for damage less than substantial structural damage, the damaged elements shall be permitted to be restored to their predamage condition.
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The question then is, what is "substantial" structural damage? And the code has an answer, in the IEBC definitions:

[BS] SUBSTANTIAL DAMAGE. For the purpose of determining compliance with the flood provisions of this code, damage of any origin sustained by a structure whereby the cost of restoring the structure to its before-damaged condition would equal or exceed 50 percent of the market value of the structure before the damage occurred.
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From the photo, it appears that the party walls were being constructed on an existing floor. Do you fall under the 50% criterion to qualify automatically for "build it back like it was"?
 
The IEBC does not require a sound transmission rating and does not refer you to the IBC Chapter 12 where sound transmission requirements are found.
Staggered studs require horizontal fire blocking every 10 feet and this can be accomplished with a number of different types of insulation which will increase the STC ratings significantly
 
ldrew, what year was the building first constructed? Do you have any certificates of occupancy?
Post #12 is correct, if the code in effect at time of original construction did not have sound rating requirements between dwelling units at that time. Then you can repair the wall the way it was originally built, depending on the extent of damage as described in post #12.

If STC 50 or higher did exist in the code at the time it was first built, and this was just missed during inspection all those years ago, you might be on the hook to provide an STC 50+ wall now. IF that's the case, you have several options. Here's one with STC 52:
https://www.usg.com/content/usgcom/en/design-studio/assemblies/assembly-detail.30226.html


1732062946030.png
If you only want a single layer on each side, you can use "Quiet Rock":
https://pabcogypsum.com/resources/sound-control-assembly-selector/pgd-ws-537-16/
1732063140340.png
 
Joe.B said:
Dude! Did you just see his last post, it is a fire repair, at the time it was built it probably didn't require an STC of 50.

You are a Troll.
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Yankee posts a lot of incorrect information.

It doesn't matter what the code was when it was built, this is a full rebuild. There is no technical infeasibility. New work need to meet current code unless that is a good reason why that is impossible; that's true for even Level 1 alterations.
 
mtlogcabin said:
The IEBC does not require a sound transmission rating and does not refer you to the IBC Chapter 12 where sound transmission requirements are found.
Staggered studs require horizontal fire blocking every 10 feet and this can be accomplished with a number of different types of insulation which will increase the STC ratings significantly
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LOL no. This is a complete rebuild, you must meet the current code. They are literally rebuilding the wall including all components necessary for sound control.
Do they need heat, lights, bathrooms which are required in Ch.12??

1732117803589.png
 
redeyedfly said:
Yankee posts a lot of incorrect information.

It doesn't matter what the code was when it was built, this is a full rebuild. There is no technical infeasibility. New work need to meet current code unless that is a good reason why that is impossible; that's true for even Level 1 alterations.
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You said “new work must meet current code”, Yes, that is true, and the applicable current code for repair work on existing buildings is Texas’ adoption of the IEBC. Yankee posted the applicable code sections. The building is fire damaged and this is a repair to that fire damage.
The Texas IEBC provides the applicable scoping for repairs, as described by Yankee.
Your response is to simply declare that to be “a lot of incorrect information” but you do not address the specific code sections that he cited. There seems to be a difference of opinion on whether repair work is by definition “new work”.
The IEBC definition of “repair”:

REPAIR. The reconstruction, replacement or renewal of any part of an existing building for the purpose of its maintenance or to correct damage.
 
Yikes said:
You said “new work must meet current code”, Yes, that is true, and the applicable current code for repair work on existing buildings is Texas’ adoption of the IEBC. Yankee posted the applicable code sections. The building is fire damaged and this is a repair to that fire damage.
The Texas IEBC provides the applicable scoping for repairs, as described by Yankee.
Your response is to simply declare that to be “a lot of incorrect information” but you do not address the specific code sections that he cited.
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I was responding to the troll comment. But, fair enough. He posted from the structural repairs section. The problem the OP presented is not at all about a structural repair, It is about the wall requirements. We can clearly see the extents from the photo that show the building down to the studs. When they rebuild that wall, they need to meet all applicable sections of the current adopted IBC code per 702.7 2021 IEBC (go read it again, it literally scopes the entire IBC for new work). There is no reason they cannot meet the sound requirements. I have never heard of an AHJ that would not require a gutted building to meet the current building code for all the new work. They need to add insulation and an additional layer of gyp or resilient channel, no technical infeasibility here.
 
Is it a repair or an alteration?
A repair does not have to meet the current IBC unless specifically required
If it is an alteration then redeyedfly is correct that all 3 compliance methods refers you back to follow the IBC for new construction.
My bad in post #13

301.1 General.
The repair, alteration, change of occupancy, addition or relocation of all existing buildings shall comply with Section 301.2, 301.3, or 301.4.

301.2 Repairs.
Repairs shall comply with the requirements of Chapter 4.
 
I agree that IEBC 702.7 is applicable to “new work”. But in the context of a repair, what does the word “new” mean?
There was a wall that was existing before, then it burned (including studs and finish surface), and the IEBC 405.2 talks about “restored” to predamaged condition. To me that’s a like-for-like replacement in-kind. The IEBC definition of “repair” includes the word “renewal”. So I think it is possible to install replacement material in the same manner and techniques that were code-compliant at time of original construction, and it will comply with the current applicable IEBC code.
If the previous wall prior to the fire was not staggered stud, but the post-fire work is staggered stud, now we are venturing into “new” territory as it is no longer replacement in-kind, like-for-like.

One other suggestion for redeyedfly: it’s great to respond on the technical merits of the code, but interjections like “how are you designing MF (for a fee!)… without understanding…” are what appear troll-like, especially since you don’t have inside knowledge as to the OP’s relationship to the project. At the time of your response, all he said was that he was working on a drawing. That doesn’t make him the design professional of record. Maybe he wanted to impress his boss by proactively being as thorough as possible, seeking help from experts on the forum.
We all have a point where we find out these things (STCs, repair vs. new requirements) for the first time. I hope this forum can be a place where people will not get accused of being unprofessional as the price to pay for simply asking a question.
 
mtlogcabin said:
Is it a repair or an alteration?
A repair does not have to meet the current IBC unless specifically required
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This is why I asked if this project falls under the 50% criterion. That determines whether it can be repaired with in-kind construction or if the replaced construction has to meet the current code.
 
Pretty sure that ain't a new wall (or replacement) and is not required to be....Get a layer of 5/8 on both sides and move on.....Or get involved and write code the way you think it should read....
 
steveray said:
Pretty sure that ain't a new wall (or replacement) and is not required to be....Get a layer of 5/8 on both sides and move on.....Or get involved and write code the way you think it should read....
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Let's "repair" the plumbing with lead solder too!

They're building a new wall, it needs to meet the current building code, it's not even gray.
 
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