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enter image description hereI am looking to install two 4x8 overhead storage racks in my garage. Will I compromise the structural integrity of my i-joist, that is, 2"wide × 1 3/8"high × 3/4" to the web if I drill vertically through the flange with a 5/16"×3" Lag Bolt that came with the racks? From what i know the top part of the I-joist is compressed while the bottom is under tension and I can't seem to find any answers on the internet, except when it comes to drill through the web. It's also a 2 story home.

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  • I presume this is a wood I-Joist? Who made it, for that matter? Commented Aug 3, 2022 at 2:24
  • Correct its wood. Not sure. On it is written Trus Joist
    – Elvis
    Commented Aug 3, 2022 at 2:33
  • Knowing how an I joist is made, I’m pretty sure the answer is no. But reach out to some manufacturers and ask them. Commented Aug 3, 2022 at 3:02
  • Wouldn't he want to contact the manufacturer of the I-joist instead of "some manufacturers?"
    – RetiredATC
    Commented Aug 3, 2022 at 3:06
  • @RetiredATC I've added a picture to my post above
    – Elvis
    Commented Aug 3, 2022 at 3:10

2 Answers 2

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In this publication from TJI it tells you where you can drill and cut the I-joist web. In bold letters it days DO NOT cut flanges.

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  • Informative, but the OP is asking about hanging a load from the flange. Commented Aug 3, 2022 at 3:00
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    I believe he is asking if he can drill through the flange, although maybe I misread it.
    – RetiredATC
    Commented Aug 3, 2022 at 3:03
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    Agree, but drilling into the flange and loading it is different from cutting the flange. Commented Aug 3, 2022 at 3:04
  • @Aloysius Defenestrate You may be correct. The technical publication has holes in various places of various shapes and groupings in the web of the I-joist. There are no holes in the flanges. An additional note says to not cut or notch the flanges. Based on that, I would not drill a hole in the flange without consulting TJI first. Maybe I'm being too cautious, but the manufacturer is still in business and can be contacted for technical support. What's the downside?
    – RetiredATC
    Commented Aug 3, 2022 at 17:23
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It’s totally fine. You can do up to a 500 LBS point load on a trus joist TJI every 5 feet. A 600LBS Capacity garage overhead storage rack will be attached to 4 separate joists at 2 different points, so you will have 8 “point loads” supporting this 600LBS capacity garage rack. That equates to about 75 LBS per point load, which is absolutely nothing. The APA manual for garage door installation states that you can hang a 600LBS garage door from engineered wood I beams. You are dealing with a very similar situation here.

There are plenty of professional garage overhead storage rack companies that install 1000 LBS CAPACITY racks on ibeams. Never heard of any ceiling issues.

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