Do Multiple TJI Joists Equal 15-Minutes?

2/17/2022

The IBC Table 722.6.2(1) states that 1/2" gypsum has a fire resistance rating (FRR) of 15-minutes, while 3/8" OSB (the product used for TJI joist webs) is 5-minutes.

NFPA 13-2019 Section 19.3.3.1.5.2(4) Item (10) discusses an exception to hydraulically calculating the system at 3,000 sqft remote area if joist channels are firestopped into volumes not exceeding 160 cubic feet.

Most volumes created by composite wood joists are much smaller than the 160 cubic feed stated in the standard, which means that gypsum board would only be required every 4th- or 5th- joist in most situations.

However, would the 3 or 4 layers of 3/8" OSB (the web of each joist) across 3- or 4-bays meet the equivalent of the 1/2" gypsum requirement?

Sent in anonymously for discussion. Click Title to View | Submit Your Question | Subscribe

2 Comments

Travis Mack link

2/17/2022 08:31:17 am

You would have to get performance testing to show that the layers of OSB would be equivalent. Also, they would all have to be placed together and not spaced at 2' on center like TJI typically are.

Most likely, if they are not filled with insulation, you will be doing the 3000 sq ft design area. Don't forget you can slide up the curve for those. In light hazard, you can do 0.07 gpm / sq ft over the most demanding 3000 sq ft. I believe in OH1 if you can get the QR reduction, you can do 0.1/4000 then use the QR reduction to drop you to 3000 sq ft. Same as OH2, you can go up the curve to 0.15/4000 and then use the QR to get back down to 3000 sq ft. You just can't go below 3000 sq ft. With EH1, you can go 0.24/4000 then use the high temp sprinklers to get you down to 3000 sq ft. This is great because you get back to 130 sq ft spacing. Then EH2 is 0.34 / 4000 and the high temp reduction to get you down to 3000 sq ft again.

This is all PRE-2022 edition. In the 2022 edition the curve have been eliminated and it is all single point design.

Jesse

2/17/2022 09:05:09 am

Agree with Travis. You'll need to get some test data on the combustibility. I think it likely you'll need to either a) extend the design area to 3,000 sq. ft. or b) fill with NC insulation.

Leave a Reply.

Home
Our Cause

The Blog
The Forum

PE Exam Prep
The Toolkit
MeyerFire University

Pricing
Login
Support
Contact Us

MeyerFire.com is a startup community built to help fire protection professionals shine.
Our goal is to improve fire protection practices worldwide. We promote the industry by creating helpful tools and resources, and by bringing together industry professionals to share their expertise.

MeyerFire, LLC is a NICET Recognized Training Provider and International Code Council Preferred Education Provider.
All text, images, and media Copyright © 2016-2024 MeyerFire, LLC

We respect your privacy and personal data. See our Privacy Policy and Terms of Service. The views, opinions, and information found on this site represent solely the author and do not represent the opinions of any other party, nor does the presented material assume responsibility for its use. Fire protection and life safety systems constitute a critical component for public health and safety and you should consult with a licensed professional for proper design and code adherence.

Discussions are solely for the purpose of peer review and the exchange of ideas. All comments are reviewed. Comments which do not contribute, are not relevant, are spam, or are disrespectful in nature may be removed. Information presented and opinions expressed should not be relied upon as a replacement for consulting services. Some (not all) outbound links on this website, such as Amazon links, are affiliate-based where we receive a small commission for orders placed elsewhere.

Do Multiple TJI Joists Equal 15-Minutes?

Leave a Reply.

ALL-ACCESS

SUBSCRIBE

COMMUNITY

YOUR POST

PE EXAM

FILTERS

ARCHIVES

PE PREP SERIES