Can you get into the crawl space and install insulation? That would be less effort.

Some people have installed "sub floor" between the joists to firm them up.

we could install insulation - and we do have some there now but it's not in great shape. We're going to put a supporting beam in too. There is a fair amount of patching that needs to happen anyway so wondering if pulling it all up and starting over would be the best thing.

Congrats on your architectural dig!

A couple potential problems with pulling it up:

1. It likely goes underneath adjacent walls, so you'd be slicing the boards off at the walls. That may reduce the support for the walls in places, because a board that used to continue under the wall to a joist is now "flapping in the breeze" and no longer supportive.

2. Installing a 3/4" plywood subfloor, which would be the correct one to install, would raise the floor by 3/4", possibly putting it above the adjacent rooms, creating a tripping hazard. Given that you've excavated down, if there are built-up layers in adjacent rooms, that may not be the case. But it may.

Are the boards perpendicular to the joists or diagonal? What's the spacing between the joists?

Photos?

HEre are some pictures. Gaps between the boards

More gaps...

Here you can see the patchwork we are dealing with, and the corner of the dining room where there is beautiful parquet - that we are keeping. It is already higher than the kitchen floor and we won't be able to get it level (it will either be higher or lower) - so there will be some kind of threshold.

In response to question - the walls are down to the studs, so that's not an issue. And extra height also isn't an issue - in fact it would be good and we planned for it when we put in windows. As you can see from the pics it will be joining another floor that is either going to be higher or lower than the kitchen area.

Boards are perpendicular to joists. Not sure of the gap, I will check.

Thank you!

I would pull everything up you can without making too many cuts, and then scrape all the tongues and the sides of the grooves, that will help getting them tight again when you re-install. Lay your 3/4" ply and then put the pine back down.

I can already tell you that it wont go back down in the same spot, so dont bother labeling each board, i.e. 5th row, 3rd board.

you wont have enough to re lay the floor in the kitchen. are the cabinets gone?

if so, you could buy new pine, or fir, and put that underneath where your new cabs will go. or install the cabinets before laying the floor, that might make up for what you lack in material.

Why don't you just lay a new floor over the old one?

We think they are besutiful and dont want to cover up.

funny - some of the floor is painted so we assumed that once it was the floor....regardless, we're going to try and finish it!

That's what you did when the money ran short!

I can relate to that...

"funny - some of the floor is painted so we assumed that once it was the floor"

It was common for a house to start with just the subfloor, and when the owner had enough money, they would install tongue and groove of their choice.

My house has a fully painted subfloor under the oak/pine top layer. And the oak was installed in the 1890s

It was also common at that time to use that wide plank T&G pine as flooring in the upper stories as well. I am currently doing a similar process for salvaging and repairing the pine subfloor in an 1885 double wythe brick farmhouse. pine subfloor is only flooring ever throughout second story with edges imbedded in the plaster. I also worked on a 3 story Craftsman Transitional that had same subfloor only in the 3rd story.