Expert: Dan Griffin - 4/2/2008

Question
During water damage sheetrock tear-out, the workers cut part way into the bottom flanges of some I-joists in the ceiling of my garage.  I asked another expert about a repair, and in additon to his plywood lamination suggestion, said to ask Weyerhaeuser, the ones who made them.  They said tear them out and put in new, fastened from above.  WELL- all the house wiring and plumbing runs perpendicular through these joists, and the floor above is glued and screwed down 3/4inch T&G plywood under 3/4 inch thick six inch wide plank cherry.  No way I want to tear out these TJI's and the floor above!  any experience that is practical to patch them?  TJI series 150, 16ft 6 inch span, 11-7/8 chord depth, 16 in on center, cuts all off center, and I have 8 ft accessible spans, 5 ft has wiring and pipes.  
good grief- what a trial."

Answer
Dave,  I really sympathize with your dilemma.  It would sure seem to me that you should be able to add an additional 2x bottom chord and glue and screw a fresh stress skin on each side.  This will disturb your bottom profile, but that's better than tearing out cherry.

I, too, would have recommended working with the manufacturer as these things are a bit new and many architects defer the structural specifics to the manufacturer.  The bottom chord has been seriously compromised and the joists function primarily in tension (the force that tries to make the joist sag or fail tends to be concentrated in the bottom).

Contact a structural engineer.  It may be possible to leave the existing I joists in location and add new dimension lumber or new I joists to carry the load, it might also be possible to add a coffer look below to carry the load.