Did they contruct oak tongue and groove flooring without a subfloor?

Yes, wasn't plywood in the old days

Hi Deadfloor

I have never seen oak T&G installed on the floor beams. The older houses that I worked on had 1x6 and/or 1x8 as sub flooring set on a 45 degree angle to the floor joists. Then T&G was installed perpendicular to floor joists.

Chuck