I had hardwood floor extended into another room. The joists were so high that a subfloor could not be put down. The floor needed to be laid parallel to the joists. The contractor put blocks between the joists with about 12 inches between the blocks. The joists are 12 inches on center. Now the floor has hills and valleys. The valleys are about 1/8 inch deep. Is this acceptable? Will the flooring over the open areas keep sinking?

There is no access to under the floor so to fix it, I assume the floor would have to be ripped up. Its 2 1/4 by 3/4 oak.

Thanks for your help.

Sounds like no one profiled the joists to all be on the same plane, before blocking.
I hope they used glue and joist hangers on every block!!!

An 1/8" in 1 foot is pretty significant.

This follows no guidelines I've ever seen.