NJ IBC - Fire Rating Between Townhomes

[nickedemus]

Hello there!

We are doing CDs for new townhomes in NJ--occupancy R-5 in IBC. I'm having a difficult time figuring out what the fire rating should be at the tenant separation walls. I must be looking in the wrong place in the code.

I've seen this go horribly wrong in the past, with a massive assembly consisting of 2 2x6 studs... I know that assembly isn't necessary.

Any pointers?

Thanks in advance and happy holidays!

 

[RLGA]

Group R-5 is a New Jersey amendment and not part of the original IBC. The amendment for Group R-5 requires compliance with the IRC New Jersey Edition. You need to go to Section R302.2 of the IRC to determine the fire-resistive requirements for walls separating townhouses.

 

[nickedemus]

Yes, I actually just spoke to a code official at NJDCA and he basically said the same thing.

Now my challenge is coming up with a compliant assembly. I'd really love to avoid the "two 1-hour fire-resistance-rated wall assemblies." Would prefer a single wall that achieves the same protection.

Open to suggestions over here!

Thanks.

 

[RLGA]

Section R302.2 says "Wall separating townhouses shall be constructed in accordance with Section R302.2.1 or R302.2.2."

Section R302.2.2 allows you to use any 1-hour fire-resistance-rated assembly (or 2-hour assembly if no sprinkler system is installed). This does not mean it has to be a double wall (which is only required if using the other option in Section R302.2.1).

 

[Paul Sweet]

Most gypsum board manufacturers make area separation wall systems. They have a gypsum core with metal clips, and a 2x4 stud wall on each side for structural independence. Here's U.S. Gypsum's version:

Area Separation Wall System

USG's Area Separation Wall System are fire-resistant systems create enhanced protection between townhouse units with shared walls.

www.usg.com

 

[cda]

Yes, I actually just spoke to a code official at NJDCA and he basically said the same thing.

Now my challenge is coming up with a compliant assembly. I'd really love to avoid the "two 1-hour fire-resistance-rated wall assemblies." Would prefer a single wall that achieves the same protection.

Open to suggestions over here!

Thanks.

This is what is used around here:

https://literature.puertoricosupplier.com/037/MO36779.pdf

I think there is also another maker.

Waiting for Santa, to come inspect.

 

[nickedemus]

Section R302.2 says "Wall separating townhouses shall be constructed in accordance with Section R302.2.1 or R302.2.2."

Section R302.2.2 allows you to use any 1-hour fire-resistance-rated assembly (or 2-hour assembly if no sprinkler system is installed). This does not mean it has to be a double wall (which is only required if using the other option in Section R302.2.1).

You know, I was staring at that, thinking it could be my way out. But then I saw this sentence: "The common wall shared by two townhouses shall be constructed without plumbing or mechanical equipment, ducts or vents in the cavity of the common wall." That made me think R302.2.2 also had to be a double wall.

 

[nickedemus]

Most gypsum board manufacturers make area separation wall systems. They have a gypsum core with metal clips, and a 2x4 stud wall on each side for structural independence. Here's U.S. Gypsum's version:

Area Separation Wall System

USG's Area Separation Wall System are fire-resistant systems create enhanced protection between townhouse units with shared walls.

www.usg.com

That is the one that I am familiar with (and hope to avoid)!

This is what is used around here:

https://literature.puertoricosupplier.com/037/MO36779.pdf

I think there is also another maker.

Yes, I was just googling and it seems there are a number of approaches (Nos. U336, U347, U366, U373, U375 and U388). Each manufacturer seems to specialize in one or another: Q&A: Area Separation Wall Design | UL

 

[nickedemus]

Yes, I was just googling and it seems there are a number of approaches (Nos. U336, U347, U366, U373, U375 and U388). Each manufacturer seems to specialize in one or another: Q&A: Area Separation Wall Design | UL

**I should add that they are all very similar in design.

 

[RLGA]

You know, I was staring at that, thinking it could be my way out. But then I saw this sentence: "The common wall shared by two townhouses shall be constructed without plumbing or mechanical equipment, ducts or vents in the cavity of the common wall." That made me think R302.2.2 also had to be a double wall.

No, the space between studs in a framed wall is also considered a cavity.