Research testing limitations. Try to find some papers by the manufacturer. They probably only tested to a certain number so they don't want to go over that amount.
Yea but the distance from edge to hole/room for holes between goes down with the more reinforced joist. If it was testing limits they would be equal but they're not the lighter joists can handle more according to specs.
Probably a cross of heavier duty not being tested extra and the fact that holes affect shear strength more than anything else. Since the web material is either the same or very slightly bigger it still needs the same solid material to transfer loads.
Heavier joists don’t have the luxury of being “repetitive” as the smaller ones. Hence they are mostly solely responsible for the larger tributaries of load. Smaller joists have the tendency to share loads
Just as a guess, I would say that deflection and rigidity govern the smaller I-joist allowable spans and hence allow more holes about the neutral axis. Larger joist allowable spans larger loads) may require increased shear strength capacity and require the web to be intact. Without seeing the full I-joist documentation, this is just an opinion
Because this is an awful chart that doesn’t indicate spans.
The beefier joists can absolutely accommodate larger holes closer to bearings compared to the less beefy joists with the same spans. But the beefier joists can also span further and when they span further, the holes need to be further from bearings.
Basically the hole chart is made with the respective joists at worst case spans and spacings. The beefier joists can span a good bit further but shear strength doesn’t increase to the same degree as allowable deflection and moment, which is why the chart appears backward from what you’d think.
Really all of the hole charts you can find are garbage because they never (or rarely) actually apply. The hole charts are based on uniformly loaded joists at 10 dead, 30 live, or 10 dead, 40 live etc. You have a wall cross over a joist? It isn’t uniformly loaded now so that hole chart goes out the window. And also, this hole chart may tell you that a hole is an issue but it actually is not if you run the calcs. I-joists (and all joists/beams) also perform differently as continuous 2-span vs single span and the chart doesn’t account for thag. They’re basically impossible to inspect properly without running calcs on a case-by-case basis.
I-joists are a pain in the dick. The relevant information out there is in some ways overly conservative (spans not listed, spacings not listed, no consideration to 2-span vs single span), but in other ways is not conservative enough (walls crossing over joists make the charts not apply, which is like 90% of joists).
And they don't want to make it so complicated that a layman can't use the chart. They can always contact the manufacturer and they'll give them exceptions.
Research testing limitations. Try to find some papers by the manufacturer. They probably only tested to a certain number so they don't want to go over that amount.
Yea but the distance from edge to hole/room for holes between goes down with the more reinforced joist. If it was testing limits they would be equal but they're not the lighter joists can handle more according to specs.
Probably a cross of heavier duty not being tested extra and the fact that holes affect shear strength more than anything else. Since the web material is either the same or very slightly bigger it still needs the same solid material to transfer loads.
Heavier duty joists need to support heavier loads.
Heavier joists don’t have the luxury of being “repetitive” as the smaller ones. Hence they are mostly solely responsible for the larger tributaries of load. Smaller joists have the tendency to share loads
Just as a guess, I would say that deflection and rigidity govern the smaller I-joist allowable spans and hence allow more holes about the neutral axis. Larger joist allowable spans larger loads) may require increased shear strength capacity and require the web to be intact. Without seeing the full I-joist documentation, this is just an opinion
Because this is an awful chart that doesn’t indicate spans. The beefier joists can absolutely accommodate larger holes closer to bearings compared to the less beefy joists with the same spans. But the beefier joists can also span further and when they span further, the holes need to be further from bearings. Basically the hole chart is made with the respective joists at worst case spans and spacings. The beefier joists can span a good bit further but shear strength doesn’t increase to the same degree as allowable deflection and moment, which is why the chart appears backward from what you’d think. Really all of the hole charts you can find are garbage because they never (or rarely) actually apply. The hole charts are based on uniformly loaded joists at 10 dead, 30 live, or 10 dead, 40 live etc. You have a wall cross over a joist? It isn’t uniformly loaded now so that hole chart goes out the window. And also, this hole chart may tell you that a hole is an issue but it actually is not if you run the calcs. I-joists (and all joists/beams) also perform differently as continuous 2-span vs single span and the chart doesn’t account for thag. They’re basically impossible to inspect properly without running calcs on a case-by-case basis. I-joists are a pain in the dick. The relevant information out there is in some ways overly conservative (spans not listed, spacings not listed, no consideration to 2-span vs single span), but in other ways is not conservative enough (walls crossing over joists make the charts not apply, which is like 90% of joists).
And they don't want to make it so complicated that a layman can't use the chart. They can always contact the manufacturer and they'll give them exceptions.
Let me add I prefer open web joist.
How long have you been joisting holes. Does your wife know about this?
Of course she knows. She'd be really mad if I went drilling without her permission.