exterior sheating joints at 2hr rated assembly - joint system, Rated Joint, Wall Joint firestop, exterior rated wall

Posted by kimover 4 years ago

exterior sheating joints at 2hr rated assembly

GC changed shaftwall construction to UL U408 wall assembly for exterior wall. There is an adjacent building next to this wall, so the exterior sheating is inaccessible from the outside. Since this is not a C-H stud, how should drywall joints be treated at the inaccessible outer layer?

joint system,Rated Joint,Wall Joint firestop,exterior rated wall

IMG_5834.HEIC1.03 MB

IMG_5833.HEIC1.06 MB

2 Replies

Posted by JESSICA STARKSover 4 years ago

Hilti Verified

Kim,

Unfortunately, this falls outside the scope of firestop. The intent of firestop is to restore the rating between two rated assemblies; however, your application is a butt joint in a gypsum wall, which would need to be addressed with mud and tape per the UL design of the wall. Firestop is not designed to replace mud and tape, so this would be a question better suited for the wall manufacturer.

Thank you,

Jessica Starks
Fire Protection Engineer

exterior rated wall,mud and tape

3 comments on this reply

Posted by kimover 4 years ago

Hi Jessica, I think we need an EJ. the UL assembly and USG confirm mud/joint are optional when square edged drywall is used on that outer layer, in our case that side is inaccessible. It seems that when horizontal joints are staggered or offset from eachother, no mud is required. The problem is that some of the gaps are unacceptable. Looking for firestopping method within the wall assembly. Would mineral wool be sufficient? thankyou

Posted by JESSICA STARKSover 4 years ago

Kim, I would first confirm with USG that mud and tape is not required there. If it is not, we have no problem providing a firestop solution; however, you will have to be able to access the gypsum board in order to install any solution that we can provide. Since this is not a typical detail, we would need to address this on an engineering judgment (EJ), which will be a custom detail showing your exact application with the firestop components required to maintain the stated ratings. Hilti is proud to announce the launch of our engineering website, the HILTI CONSTRUCTION PLATFORM (HCP). This platform will be the home for all of your Fire Protection Engineering needs, including Engineering Judgment requests. You can find more information on how to access this new platform here: https://www.hilti.com/ej (US) or https://www.hilti.ca/ej (Canada.) Along with HCP, Hilti is excited to announce our new mobile app for all your firestop needs: Hilti Firestop Selector. Using the Firestop Selector app gives you easy access to the Hilti Fire Protection Design Team from the jobsite, on the road, or in the office to request a new EJ, an EJ Revision, or ask a Question anytime, anywhere. You can download the app on the App Store or Google Play Store. If you have any questions, please reach out to our customer service team at 1-800-879-8000 (US) or 1-800-363-4458 (Canada) for assistance. Thank you, Jessica Starks Fire Protection Engineer

Posted by kimover 4 years ago

I understand this is a butt joint of gypsum board, but it is part of a 2hr fire wall rated assembly. I haven't seen exterior sheating (exterior side and in this case inaccessible) getting mud and tape, but I'll ask usg? I thought this could have been considered as a "linear opening"/interruption that needed to get firestopped, because the wall IS the rated assembly. thank you.

Posted by kimover 4 years ago

please call me at 917.202.4096 to discuss