It's lunch time and for some odd reason I'm hankering for a sandwich!

That's quite an assortment you have there. Can you measure the thickness of each layer or possibly take a picture with a ruler next to it to give come idea of the thickness of each layer? I'd say the bottom two layers could be subfloor and floor but they look to be about the same thickness as the parquet squares which are typically only 5/16" thick.

Thanks! Here is an update. The bottom two layers seem to actually be part of the same layer, which is about 1" thick (they look like separate layers in this picture because the bottom half is painted brown and there is a groove...but I'm fairly certain it's one layer). The layer right above that seems to be made of some cardboard-like material.

Here is an annotated photo:

Also, I've studied the upstairs floors a bit more carefully and I think (but I'm not sure) that there is no additional subfloor underneath. So the pine floors are the subfloors, which I'm now using as floors. But this doesn't seem to be a problem upstairs, so maybe I can do the same thing downstairs?

Funny, I was just going to suggest that what you're calling a floor might actually be subfloor. Without taking anything up, you might be able to verify this on the upstairs floors. Two indicators are nails that line up across the floor since they're nailed into the joists, and end joints that line up so they fall on a joist. Having the end joints a consistent distance apart would be an indication there's only one layer. This distance would commonly be 16" but I'm not sure how long that has been the standard (or if your house was built to a standard).
You might have something usable under those layers but be it's wise to be prepared to find some type of damage.

There's definitely some alignment of nails, although not all boards appear to be nailed into all joists (most of the boards stretch nearly the whole way across the room).

Since the wood is pretty thick, couldn't most damage be sanded out? Also, any idea what the layer right above the subfloor could be? Would that have been laid down to separate the subfloor from the parquet tiles?

My guess would be that the cardboard layer is some type of insulation that's not suitable to glue parquet to, so it was covered by a thin layer of plywood. I've seen something similar here called homasote that had wood floor nailed through, but i think it was 1/2" or 5/8" thick.

When I mention damage I mean something that couldn't be sanded out, like water damage, rot or termite damage. You might also find that a wall's been moved or flooring has been removed to access a utility for repair work. It could probably be patched but you'd have to find something suitable to patch it with.

Gotcha. It seems like I basically just have to decide whether or not to risk it.

That's accurate. It's easier if what's covering it is really bad but you should have a plan B if you unearth something ugly.

I vote for exploratory excavation. You can always cover it all back up.

Thanks, I think that's what I vote for too. It would just be awesome to find the pine in decent condition underneath all those layers.

Update! I uncovered a small patch (about 2" x 4") and sanded the wood down a little bit. This is what it looks like:

Anybody have an expert opinion about whether this is pine? Seems like it's the right color and pretty soft...

Yes based off that picture, it looks like pine.

Yes! Is there anything I can do to be more certain? I'm thinking of applying a layer of polyurethane to that small area to see if it looks similar to the floors upstairs.

Tear out more!

We've got heart pine in our 100 yo house, and it's not soft by any stretch of the imagination. There's a difference between pine then and pine now.

wowzers!

Im just glad you aren't intending to tile this hodgepodge.

Tear out more because it looks promising, or because you can't tell?

I ask because in order to tear out more, I need to start removing trim and really committing to pulling this floor up. So I want to be at least fairly certain that there is pine under there before I do that... whether there will be damage to some parts of the floor is obviously more of a toss up.

Any trim torn out can be put back.

I say tear out more to determine what's really there. That small section looks like dimensional lumber to me, not hardwood.

What's your plan B if there's not the original pine under there? Leave the fake, horrible laminate? Or find something authentic to put down? If it's the latter, then there's no harm in tearing out what you've got. At least a bit more to find out. So take out a baseboard and go a few feet wider.

I'm with everyone else here...tear it all out. The trim can be restored or replaced...the very old wood will make you smile.

Just wanted to update everybody on this thread... we finally found the time to move forward on this project. We ripped up 4-5 layers of flooring in our living room and dining room, including (1) laminate, (2) insulation layer, (3) parquet tiles, (4) plywood, and (5) some sort of cardboard base, along with two large jars worth of nails, all of which revealed...

Thanks to everybody who provided input and encouraged me to go ahead and do this. This is 10x better than the laminate we had before.

Looks great! Thanks for the update.

Beautiful! Glad you took the plunge. And came back to share