Engineered I-joists with large unauthorized holes cut through their webs are a concern because:

The web of an I-joist carries shear, and shear is highest near the supports and lowest at midspan — which is why manufacturers publish hole charts specifying maximum diameter and minimum distance from bearing points rather than a single blanket rule. A hole placed within the permitted zone removes material where little shear is flowing; the same hole near a bearing removes material where nearly all of it is. Unauthorized holes are a problem precisely because someone cut them without reference to that engineering, so size, location and proximity to other holes are all unknown quantities. The inspector reports the penetrations and refers them to the manufacturer's tables or an engineer, since whether a given hole is acceptable is a lookup, not a judgment call made on site.

The web resists shear, and permitted hole sizes and locations are engineered around how shear is distributed along the span. Unauthorized holes bypass that engineering, so their acceptability is unknown until checked against the manufacturer's chart.

Engineered I-joists resist bending through their flanges and shear through the web. Manufacturers publish hole charts specifying permissible diameters, minimum distances from supports and minimum spacing between holes; penetrations outside those limits require engineered repair.

Shear Lives Near the Ends. A hole at midspan is often fine; the same hole by the bearing is not. The chart knows, you look it up.

Distinguish web holes from flange cuts. Web penetrations may be permissible within limits; flange cuts never are.

• •Judging a web hole acceptable by eye rather than by chart
• •Treating all penetrations the same regardless of distance from bearing
• •Assuming engineered lumber is simply weaker than solid lumber