dpb wrote:

Sounds like it wasn't addressed in the design that the contractor
hired the engineer to do the structural but probably didn't provide
him with the necessary inputs to know where the venting locations
were to design around existing or account for them for the
incorporation of existing locations.

That it was in a gc's scope to ensure that would also be somewhat
dependent on how contract was done -- were you the gc subletting work
or was the contractor the actual gc? That may have bearing depending
on local rules/law...

I'm wondering if the OP will post a link to the contract so that we can see
what the contract and bid actually stated? Scan them and put it onto
tinypics or some such website. As you stated, it would be nice to see if the
contractor hired was limited, by bid, to a specific scope of work, or if he
had the authority to subcontract with other trades. Did the bid specify just
the structural work with the OP acting as GC? Or was the bid for a GC to
develop the scope of the work needed to be in compliance with all affected
codes?

If I hire someone to re-do my ceiling, and that is all my bid called for,
then the only permit needed would be the specifications for the things
needed to properly support the ceiling. The contractor wouldn't assume
responsibility for oversight of roofing contractors or HVAC specialists.

--
Dave
www.davebbq.com