I’m installing a toilet in new construction. Unfortunately the position of the toilet was changed so that now the 12″ location for the flange is directly over a TJI joist. What is the minimum distance the center of a flange can be to a joist? What other options do I have? Headering the joist will be very difficult.
You have no choice but to cut out the offending joist and double-header it (creating a box in which to drop the closet bend). The only other option is to reposition the toilet. You should use plenty of metal re-inforcements, such as Simpson Strong-Tie connectors. This seems like a situation where the carpentry contractor screwed up, and I’d suggest doing what I do in such situations…vent your frustration by cussing them out, and go ahead and do what it takes to get the plumbing properly in place.