I-Joist Cutouts

Ran across this one on a new build. LP Solid Start I-Joists (LPI 32 Plus). When I spoke to the onsite HVAC installer, he told me the Manufacturing Plant sent these with the holes already cut out. I don’t know of any I-Joist that allow a full cutout and everything I find on the LP website says this is wrong (https://parr.com/PDFs/LP%20I-Joists%2020plus,%2032plus,%2042plus.pdf). Never know what you are going to find. Comments?


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From the manufacturer; LP® SolidStart® I-Joists are more versatile than open web floor trusses and more uniform and dimensionally stable than lumber. Wider flanges ensure that the floors you build are sturdy and stable. I-Joists can be trimmed on-site, and long lengths allow ceilings and floors to be designed with fewer

Note the web cut-outs along the flange, likely for ductwork, and refer the consultation you enacted with the HVAC installer.
Here is what I might write.
Observation: Structure: Joists: LP® SolidStart® I-Joists. I-Joists Webs trimmed in a straight line.
Recommend: Refer Webs trimmed to the HVAC contractor immediately.
Limitation: Residence under construction.

Thanks Robert! I have a call into the Plant Mgr of the construction company. I’ll get them to buy off on it or not. Many Thanks!

Not a chance.
That will require repair and the contractor that cut those gaping holes will be on the hook.


If the holes across multiple joists are centered, the corners of the square holes are round cut, and the cut lines are mostly straight, then the holes are likely prefabricated. Notice also the sliver of OSB web left toward each flange. IMO 9/10 times field cut holes by contractors will not leave this sliver of OSB left, which is actually required by many manufacturers. Again, another indication the holes are prefabricated.

With large holes in I-joists, go by the hole charts provided by the manufacturer for inspection, but do realize that the holes can actually be even larger than the allowable round/square hole sizes on the chart. Larger holes will need to be run with software and depending on the loading, location, size, etc, they can still work.

Why would you refer the structural modification of an engineered I-joist to the HVAC contractor? This recommendation makes no sense. This is the first time I’ve heard of an HVAC contractor that is able to determine whether a structural modification is acceptable or not.

Clearly, this is a predrywall inspection. The easiest way to check if the holes are prefabricated is to look in the permit box for the I-joist plans/placement plans. They will have the required blocking, prefabricated hole locations, I-joist series, I-joist depth, point loads, other required reinforcement, and installation requirements. If the plans aren’t there or if you are uncomfortable determining if the holes are prefabricated or not, then recommend having the web holes checked by the I-joist manufacturer or the I-joist supplier.


Looks like a field modification from here in GA.


I’m thinking these are not field modifications. All the holes lined up perfectly. Funny thing is, all the ductwork was in place and the holes aren’t being used. It was a two-story home (these being the joists for the 2nd floor) on a slab with the Furnace/Air Handler in the attic and the supply lines were all in between the joists. My take on the Mfr Specs is that a minimum of 7/16” OSB is required on the top and bottom. I’ll report back.

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Agreed. Looks like reciprocating saw was used.


The OP makes a good point about them being all in a line and not being used. The ones I see that are cut by the manufacturer are really clean/precise. Maybe that varies more than I am aware.

If this was a new build, it should be easy enough to to track down which lumber yard they came from to verify if they were originally ordered with the cut-outs. It does not look like it was done in the field with those round corners. A sawsall does not make round corners without a pilot hole and the radius is to small for a jig-saw. A router from the factory seems more likely.


IMO, It looks like a field modification from here in Maine.


Did you check page 15 of your PDF? you can have a square hole just like in your pics up to 14 inches in 16"deep LPI 32+ which is pretty much what you have. Did you take some measurements, clear span, the distance to the hole?


Hi Simon, Yes I did. The holes were about 8 7/8” (the entire web) X 11”. I found the chart on P. 15 difficult to pin down “Exactly” what is allowable. It seemed the maximum allowable was 8” in depth—leaving 7/16” OSB before the flange on both the top and bottom. Illustrations on P. 15 show this also, although they are not part of the specifications. Cutting out the web from top to bottom didn’t really pass the “smell test” for me and the specs “appear” to back this up, but I can’t quite get to 100% on this answer. Thanks for your help.

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When I spoke to the onsite HVAC installer, he told me the Manufacturing Plant sent these with the holes already cut out.
Funny, isn’t it. Lol.

If all other requirements are met for hole (in this case rectangle shaped) size, then this note would be applicable from page 15.

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How deep was the joist (web+flanges)? 14"?

Thanks Ryan. I believe that is the answer I needed—should’ve found that myself.

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Joist was 11 7/8”

Sometimes just needs a fresh set of eyes! :eyes:

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The hole would work in span of up to 10 feet, beyond that it would have to be engineered. Also if you want to get picky with 1/4 from either side of the flange… It looks like they left some meat on the web 1/8-1/4"

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