What's the term that's used when,
Instead of laying plywood on the floor joists ,
They put down one by four inch hardwood diagonally ,

Before installing either carpet or hardwood flooring.

It was on early 1900's better quality homes

My first thought would be real hardwood flooring. Terminologies may be different depending on where in the US you are located. Might be called slats. Some places they would call it “Pergo”. I’ve heard people call tongue and groove hardwood flooring “Bruce Flooring”.

I hope this helps for what it’s worth.

from what I have read, it is a plank or lumber subfloor.

Not a very fancy name, but probably less fancy names back then.

A house I built in 1980 had a fir plank roof sheathing rather than plywood cause it was cheaper back then. Looked crappy during install, but never had a problem with it.

Plank subfloor.

quote:

Originally posted by sigmonkey:
Plank subfloor.

^^This. A previous house I lived in and remodeled was built in the late 1940's. Walls were plaster & lath. Floors had plank subfloor like you describe, with 3/4" tongue & groove red oak hardwood installed over it.

You can see the original plank subfloor in the picture below. I removed a wall and had to patch in new 3/4 red oak. I also laid the new plywood subfloor.

I could be wrong, but I think what we think of as plywood subfloor was used in residential construction starting in the late 1950's or early 1960's?

That is a plank subfloor.

My house was built around 1900.

When we ripped up a bathroom floor that was underneath.

That's it thanks folks,
The TV show that I saw it on , said it's the way it should all be done.

They didn't go into any detail as to why it was so much better.

My house was built in 1940.

Still has original hardwood floors (like the image above) in the living room and dining room.

I will be pulling the vinyl and carpet and (hoping to) see if I have more hardwood.