Your architect should be able to refer you to some modular builders.

I'm building a duplex and using a lower cost builder who doesn't do any of the site work. 

If not try to get an injunction to stop construction from a judge, up your flood insurance, there are a few different ways to deal with the situation or the blow back in this case.To me is sounds like the builder made a error in his engineering plans, and he knows it.

Yep, the architect and builders who conveniently, for them, dont get to change or dissolve their LLC or company after every new construction.Besides liability there also the problem of selling and zoning.

Adair is a longstanding Pacific North West custom home builder with a reputation for speed and efficiency. 

I would get the advice of local reputable builder that currently builds in your local municipality. 

Now it's getting into the builder side of things.

How’d you find your builder?

In our mind this will likely not be recoverable from the builder or association but hopefully a shared cost between both home owners insurance.

Ask friends, local groups, builders, online forums, meetups, investor groups, visit flip job sites, etc.