I think it makes a difference whether the plans had to undergo an approval process with the AHJ, before construction was allowed to begin. If the AHJ had approved the plans, and if you now want to change what is shown on the plans, I think you will need to get approval for those changes. Much depends on the nature of your company?s relationship with the engineering company. If the engineering company has a contract to provide the owner with support during the construction period, then it would include some type of design change process. You could submit a Request for Information (RFI) or other form of communication, to initiate the change. But you can?t make a change without some type of approval. ?The client says they don?t want . . .? is a good reason for a change, but it does not constitute approval of that change.