Is it unusual to have floor separation that a nickel can fit into? It's red oak number 2 and it was installed 2003.

I would say that is not uncommon, but that don't make it right either.

It sounds like you have a sand on-site oak floor. If you do the site-finished men are constantly called on to install the floor no matter what. They normally don't have the luxury I am afforded to insist on acclimation and the HVAC up and running, ect.

But , having said that, they should at least be doing moisture testing to minimize that. Where I live I have never witnessed a moisture test being done.

I'm in a new house laying the tile and then here comes the oak flooring delivery, then the installers will roll in, and by lunch time she's going down on the floor.

I see it all the time nowadays.