huangyhg

repair of wood i-joist
has anyone successfully repaired the flange of a i-joist? mechanical contractor decided to remove half the flange to make room for ductwork. naturally in the zone where bending strength is required!
you didn't indicate if they removed the compression flange or the tension flange. i am assuming that they removed part of the tension flange so that there is only a small clearance between the duct and the bottom of the flange.
the first thing i would do is require the contractor to submit a certified design for a method or repair. that way you force the contractor to do all the leg work and pay for the cost of tracking down a solution. also keep in mind that the contractor probably cut the flange to save time and money. if he is reluctant to pay another engineer to develop a solution you might point out to him that your solution is likely to cost him more time and money.
if you are required to come up with the solution you are probably being pressed by the architect and owner to come up with a quick solution with little or no pay. a solution might involve the contractor removing his duct work so that the i-joist can be reinforced with a smaller opening designed into it to accept a smaller duct which the contractor has to buy and install at additional costs.
another reason why you want to put the burden of finding a solution on the contractors back is that it probably involves contacting the joist manufacturer for their input. which the contractor can do through the joist supplier.
a possible solution might to add full depth plywood on both sides of the joist to creat a box beam. the plywood could be glued and screwed to the joist flanges. another possibility if the tension flange is damaged is to attach a light gage steel channel full length to the underside of the i-joist flange.
part of the solution will depend on the material used in the i-joist flange. if it is a laminated veneer flange the use of screws may case splitting of the flange. if you are only dealing with one joist, then clamping and gluing of side plates may result in enough additional strength that the contractor can sleep at night.
thinking from the perspective of an attorney - unless the contractor asked and received permission from the architect or engineer of record to cut the joist, it his responsibility (to repair or prove it is structurally acceptable) and the liability is his. by advising him of a repair method, you will likely assume a large share of his liability. i would advise doing nothing more than requiring contractor to submit his plan for the repair, or his analysis which shows the joist is structurally sound - for your review: or put it back like it was and change the duct alignment to accomodate the truss without cutting.
i completely agree with cvg. there are methods of repairing these but i would leave it up to the manufacturer to give the repair because of liability issues. i would agree with the plywood box beam thought and would also consider a steel plate with lag screws. you would have to pre-drill the lag scews to resist splitting.
the manufuacturer of most i-joists specifically say that you can not cut either flange, period, no question. that is a huge liability. if it were my personal house though, i would make him take it out and re-install one that is not cut.
we send away to lp all the time to get repairs from their engineers when this situation arises. diagram the joist that was damaged and send it off to your supplier. they should be able to tell you what needs to be done.

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