Someone I know was replacing their oak hardwood and as it looked to be in great shape I asked if I could take it. So they pulled it up and I picked it up and hauled it into my basement and begun the laborious task of removing the nails.

I have noticed however that although the wood being in very good condition, the bottom on the groove side of each piece is cracked and somewhat loose. (which I assume happened in the removal process)
Tongue and groove still seem to fit snug,
but I was wondering if I should use wood glue in the installation to achieve greater stability, or if I should stop right now because it is beyond repair I would be wasting my time if I tried.

Look forward to hearing from you

Hard to say without knowing the extent. You may consider a combo install of gluing to the substrate and nailing.

If its thin solid wood as long as your floor has no moisture, you might be good as long as the cracks are not huge, you should be good to glue it.

If its like 5/8 thick wood, you cannot glue it and would need to nail it - and if its cracked, that will be a headache.

p.s hopefully you dont live close to the beach =)

Thank you for your prompt replies,

realized: it is tongue and groove wood that's about 3/4" thick. The face of it is fine, it is just the piece beneath the groove that cracked most of the length of the piece of wood. So I was definitely going to nail on the tongue side like usual but was wondering if the cracked groove side would need glue to stabilize it.

Floorologist: the cracks seem to run from 70 - 90% of the length of the boards. Cracks are varying lengths, sometimes overlapping and sometimes there are 1"-5" areas on the groove that are crack free. They can run along the depth of the groove to an 1/8th above it. So the tongue part in most cases fits snugly in but is only being held by a little bit. The cracks in most cases go completely through so I could pull the pieces right off if I tried hard enough. Tongue side is intact to nail through,
would it be better to put glue in the groove instead of on the substrate?,
or is that kind of cracking too severe to be workable?

That's a good one. We may here some other opinions here, but IMO you should be o.k. running a bead of PL Premium on the underneath side of the groove edge, to the substrate, then fastening.

The bottom of the groove section is compromised, therefore not being held down by the tongue. IMO you would be holding down that groove side, using the adhesive. Otherwise with any future movement, there's really nothing locking that edge down to the substrate.

I agree with Howard. The cracked groove will be an issue as that is what keeps that side of the board down and aligned with the the previous board.
How many square feet are we talking about. I thing it will be more of a hassle getting the boards to line up and banged together with broken grooves. It's just oak go buy some new wood and have a nice fire (outside) with the old.

Thank you Howard and Jeff,

I'm working with 168 sq feet which doesn't seem to bad, but then again I have never installed hardwood. It does seem that glue would be feasible for that kind of space. The boards seem to fit together well despite the cracks,
I did wonder however if I ended up needing to use some felt liner to level the low areas, glue would not work in that case.

so yes, I guess I am still wavering between making it work, or having a bonfire.

I don't see any problem with using felt for leveling. Obviously you would need to cut the felt back where gluing.

Ok,
just thought that since the cracking was quite extensive, that would mean I would be putting glue on the full length of most boards making it difficult to have the felt underneath

Well...now your bringing flatness into the picture along with the cracked tongues. What is the extent of out of spec flatness we're talking about? If it's minor, it's possible to cut back channels of the felt for gluing. Tough for us to answer, without knowing the extent.

You can always top nail the whole floor. Or...it's only 168', purchase some other material.

I haven't removed carpet, or furniture for that matter so I am making a bit of an assumption on the out of spec flatness. The house is 30 years old so I am guessing there will be some dips and rises. But like you said cutting channels would work to continue securing with glue. And in the problem areas I'm sure the odd top nailing would do the trick, thanks for the advice.

It is only 168'... it is however out of our budget at this point for new hardwood. But like you said, some other material may be better, and if this used hardwood looks to be to much trouble I may wait a few years and look into new hardwood or carpet depending on how the budget looks then.

thanks again for your help and advice