Hi, Jennifer,

An on-site inspector shouldn't be the one demanding structural calculations be performed; that's part of design and should have been required in order to obtain a permit. I suggest you check with your building code official for clarification about what, if anything, may be required by their office in order for you to swap the siding for stucco.

The building code is what the inspector says it is on the day he says it. These guys can and do ignore their own signatures on approved drawings.

Is this a remodeling?

The inspector may have seen an issue, and it may be in your best interest to do what he asks.

Yes, it is a remodel. According to the calculation engineer and architect of 30 years of experience. They have never requested before and it is unusal.

"The building code is what the inspector says it is on the day he says it." Building inspectors and code officials are not infallible when interpreting the code. When in doubt, ask them to cite the specific portion of the code at issue. If they can't cite the specific code requirement or you disagree with their interpretation, there should be avenues for appeal. Here in Virginia, we can appeal a building inspector's ruling to the lead inspector and then to the building official. We can appeal the building official's ruling to the state's technical review committee.

The only exterior wall structural issue I can think of is lateral bracing and uplift resistance of the walls.

What is under the siding ... structural sheathing, diagonal bracing, nothing?

Are you in a high wind or earthquake zone?

Did you increase the width of or add openings?

Post some photos.