From my experience this is not common. The joist and bandboards need to sit on CCA sill plates.These plates are secured with 1/2 bolts put in when the foundation was poured. The joist and bandboards are toenailed to the sill plates.You didn't say if yours is secured to the foundation somehow. If not,what would keep the house from moving or slipping in strong winds. I'll let someone else step in with ideas on how to fix this,I don't like my ideas.Let us kniw if you can see how they're secured. Ron J.