...structural engineer screwed up, or the GC screwed up. My money was on the GC (I would know...I work for one!) As much as I'd love to point fingers at the city inspectors, I think it's unlikely they are to blame in this case. I don't know exactly how New York's inspection office operates, but here in the Richmond area, none of the municipalities perform structural inspections. They require third-party inspection agencies to perform inspections of critical structural components, and then those third-party agencies provide reports to the building inspector/plan reviewer, which typically does not occur until the very end of the project. I've never been involved in high rise construction, so perhaps there should have been a failsafe that would have required inspection/approval of the reinforcement steel prior to any work being performed on the addition, but I have a feeling this situation is largely due to the general contractor jumping the gun and pushing to make progress on the addition due to schedule pressures and either willfully ignoring the risks of doing so without structural reinforcements in place, or doing so out of ignorance. I am willing to accept either case as being likely.