FYI - I have looked at several I-joists that have been damaged by water and/or dry rot over the years and from an engineering perspective 99% of the time you can’t salvage or strengthen these damaged I-joists. Physical damage such as a hole too big in the web or a small section cut out of a flange by a plumber can typically be repaired. This can only be accomplished if the remainder of the I-joist structural properties can reasonably be determined to be like new. Dry rot damage breaks down the wood cell structure and can damage the tension, compression and shear properties of the wood for several feet beyond localized damage from a water leak. A critical factor unique to I-joists is the bond strength between the web and the top and bottom flanges. Wet crawlspaces can damage large sections of multiple I-joists in a few years. The attached photo shows a severe case where the main sewer line was disconnected in the crawlspace flooding the ground surface. The point of this topic is I-joist damage due to dry rot is likely much worse than it looks.
If you’re a new inspector take a screwdriver with you during a crawlspace inspection and stab the side of a new 2x10 or one in good condition to get a feel for how deep it goes into the wood. A screwdriver can easily punch through a rotten 2x10. You should also practice on I-joists, especially the web. The OSB web material usually breaks down much faster due to dry rot than sawn lumber.
