What are the contractor's contract and work specifications stating: follow the code or the client requirements? Which one prevails over the other?
If it is not clearly stated, then this is a contractual flaw and this requires resolution asap.
Remember whether the contractor will build the asset is subject to local legislation, regardless what is in the contract!
* Finding a solution is great * Knowing how to implement it is fantastic * Believing it is the only one and best is naive ?