Very cool!

I am not at all an expert but I *think* this may be the subfloor. See how it's lower than the thresholds and the seams between boards are quite wide? If I'm correct he intention would be to cover it with nicer wood. I could be wrong though and others will be sure to point it out (as they should!)

I would replace it, and I don't say that lightly. Usually I am all for preservation. But in your case you could get a nice new level subfloor with beautiful hardwood throughout. And you could salvage some of the nicest pieces of the floor you remove, plane it smooth, and create a headboard, or picture frames, or even a coffee table. That way you'll be honouring the history and preserving the building in the best way possible. A solid new subfloor will give these rooms 50+ years. Not so refinishing the existing.

Yes they can. Try oxalic acid it will lighten or bleach the wood back to new. Of course I cant see the exact extent of damages. The acid lighten the wood considerably.

These floors not only have paint on them, they may also have all kinds of glue from having had linoleum on them in the past, they may have had wall to wall carpeting over them, or who knows what.

They are really not worth you spending a few grand on refinishing them.

Only do what you have to to put something else over them.

The floor is junk. Replace it.

Nope. Not worth the effort and expense, IMO. Too many large gaps and it's probably really squeaky judging by the condition.

Get a pro onsite. Depending upon the thickness of the product, it could be sanded and refinished. Anything squeaky can be addressed during the prep stages prior to refinishing.

Have an experienced hardwood flooring installer come and examine the flooring. Pictures can only show so much. But, if possible, please restore them. As Joseph stated, you might (ok, will) have gaps and squeaks, but, that comes with the territory.

And, that is why you probably bought into a 108 year old building. I am jealous, although I wouldn't live in NYC for any amount of money. Way too many people. I like my town with 1500 people.

Too bad OP never came back, I would have loved to see what they end up doing.

Well it has only been a week since they posted. I think the spaces are just old age and the wood is really dry for sure. You will need to get a pro to see if it is worth redoing but it can’t hurt to find out.

Thank you all for your answers! It is true that I like old buildings and apartments so will definitely get a pro come in and see what we can do.

Our application is currently being reviewed by the co-op and I am hoping to be able to get in the apartment with pros in a couple of weeks. Will keep the thread posted on the decision!

It looks like subfloor to me, too. I had a 1925 bungalow and that's exactly what the subfloor looked like. Here's a question not asked: What's the air infiltration like? How far apart are the boards? Look at those issues and take that into account. Usually I agree with Joseph but not here. I'd find a beautiful hardwood to put in and if budget allows, you might be able to get something reclaimed. These just look too rough and not tight enough together. NYC winters get cold, too.

Of course one expensive option would be to remove the flooring and flip the boards then re-install and sand them. I've seen that done, too.

The bedroom's floor looks like a subfloor with gaps between the boards. The living room photo isn't clear.

Please post again after you bring in the pros in a couple weeks to tell how it turned out.

I'm going to dissent on whether this is subfloor. Subfloor boards here are generally laid on the diagonal. If they weren't, I would think the end joints would each fall on a joist. That means joints would line up across the room at regular intervals (often 16" apart). I can see joints in the bedroom picture that don't line up.

As long as there's enough wood above the tongue and groove these floor should be able to be refinished. I'd caution against filling the cracks. Quite often they're the result of seasonal changes, but more likely were caused by a catastrophic event (or events). This means the floor is likely to be loose. Loose floors will move when walked on and the filler will work it's way out. If you walk on the floor with bare feet (and are weighty enough) and can't feel movement, you can risk having them filled during the sanding process. If the floor does move, the filler usually comes out of the traffic areas first making them look bad compared to adjacent areas where the filler is intact.