If you remove the floor itself the sub floor should be checked for moisture content. It should dry out a little faster, and may have been protected by the floor above and any ceilings below. Make sure the testing is not just the surface, but the thickness of the wood. Deep pins or electronic RF meters are better for this. Short pins and surface contacts do not make the grade. Any decent wood moisture meter has a depth specification. Whomever participated in this should be fired. The GC should know better than to even consider installing wood floors in unsealed or uncontrolled (no HVAC operating) space, as should the flooring installer. All the water in the drywall mud has to go somewhere. Setting type mud is a little better than pre-mix, but still introduces plenty of moisture. Even latex paint adds a lot of moisture to the house. Framing lumber is not dried to anything like its final value inside a house. That is why shrinkage and cracks in walls can continue for over a year as the framing continues to dry out. My floor guy will not even think about laying strip hardwood until 2-3 weeks after the drywall is done, the first coat of primer applied. Even longer fr wider flooring, or any species he knows to be a PITA with warping. Many of the imported foreign woods are inadequately dried from the start. Neither he nor I make money on having to fix mistakes. The main products of burning is CO2 and H2O (water in vapor form). Kerosene heaters (AKA torpedo heaters) kick out a LOT of hot water vapor that gets into anything made of wood. Propane, natural gas, oil fired, etc. (anything with a flame) does about the same.

You need to do a little more archeological digging still. You need to know the whole construction of the floor before you can decide how best to install something new. I'd take up that plywood piece in the kitchen and see what's under it. It's higher than the surrounding floor, so needs to go. You should also be able to see from there what subfloor is under the original kitchen hardwood. It's too bad the space under your entryway is finished, but I'd still do some exploring from below to see what's under there, and to figure out the fix to stop it from squeaking. Is it drywall below or a drop ceiling? I know it probably seems like a pain to tear out drywall, but if you cut out a clean patch, like 2' x the width of the joists, it'll be relatively simple to repair. Just make sure to cut it down the center of the joists so that there's room to screw the patch piece to it later. Cut the hole under the area that squeaks the most, if you can. Have someone walk on and watch the floor from below to see what's moving. It might be as simple as pounding in a couple shims from below, or face-nailing a loose board from above. You want to find out what's underneath the hardwood. It might be laid directly on the floor joists, or there might be 10" wide boards that the hardwood is nailed to. Another thought is to take out a board in the hallway, since that's not original and you want to replace it. See what the subfloor is there. I am a bit puzzled at why, when you've stripped the kitchen down to the original hardwood, it's still higher than the hallway floor. Is your current surface perhaps not the original kitchen hardwood? Peeling back the plywood area will help determine that. BTW, I haven't heard of that stop squeaking product you linked to, so can't offer any personal opinion. And don't pour self-leveling compound over top of hardwood. It needs to go over plywood.

SJ McCarthy, our contract is stated we are responsible for the materials and we pay for the labor. Unfortunately we never met nor discuss with the owner but only discussed in details ( in the proposal) with the project manager who is the solely the carpenter.) We just found out there were a lot of the DETAILS from the proposal were not explained (per the PM,but who knows) in detail to the owner or almost like "bait and switch" - for example like item #2- he spent more time because the owner did not get him another helper to help him- I told him this should not be the customer's expenses-Anyway we are willing to pay for it. The owner was offering to renew and establish a new contract from the original contact ( we felt that he cherry picking the items from the proposal, we marked them up then again he decided not to included) for the unfinished works . Once he agreed in our 2nd meeting (another example: he agreed tiling our study room to be included from the original contact in our 1st meeting then when he write the REVISED CONTRACT- he wants to charge us ), but again we are facing the same old stories-he tried to change the wording. We were burned so many times and now we diligently review line by line knowing the owner's personality. He kept saying he lived by the contract-then I told him then he should honor the low estimated to install our engineering hardwood floor including removing the carpet-in the end he says he would honor but he did not including the cost in the new REVISED contract which we add into it - we are so tired with his games. So now we put a contingency - once we agree with the new contract, no more additional expenses from the previous work was done- and we do agree that we need to be notified first and need both signatures for additional expenses from the new contract. and no more point finger of "not included" since we have discussed in detailed and are in the contract. The new addition has a hardwood floor installed - with Dri-core. Once hardwood floor was installed- they are some areas squeak- we were told by PM -put a marked up then he would fasten without explaining to us-these would be additional ridiculous charges (PM told the owner, too-we told PM that they should explain it to us- ) Regarding the installing the engineering hardwood floor is for our existing rooms(concrete slabs that has plywood already)- we are told just to put a vapour barrier. Is it possible to let me know what brands for the glues have to be moisture resistant ($2/sf) or moisture PROOF ($3/sf).? The manufacture instruction suggests to use Franklin Tongue and Groove adhesive (cross linking polyaliphactic emulsion glue) www.titebond.com -any suggestions? This Applachian engineering hardwood floor - FLOATING only needs GLUE between the wood (tongue and groove per the manufacture manual ) then would be FLOAT - this is not to be GLUE DOWN on our concrete floor (could be glue down if necessary but not in our case). Here is the website- on PAGE 9 http://www.appalachianflooring.com/uploads/general/documents/engineered-installation-guide.pdf We trust the PM and we pay for it- we just want to move on and complete the project-It has been almost 10 months. We have to do what we have to do to protect ourselves now- The owner refuses to install our towel bar in our new shower without charging us, and we told him we will take care them by ourselves. I will update this post and hoping for a better solution. Thank you

As Greendesigns points out, laying hardwood over concrete is tricky. A permanent hardwood (glue/nail/staple) on slab is more likely to go wrong than right. To be crystal clear, you can GLUE DOWN hardwood STRAIGHT to the slab. Adding plywood is a step used to NAIL down (or cleat/staple) hardwood into place over slab. You can SKIP this part if you GLUE DOWN the wood. But....and this is a MASSIVE 'but'....the professional must be SUPER EDUCATED as to glue down technique, glues, trowel size, coverage, moisture mitigation, etc, etc, etc! Gluing down hardwood is no different than gluing down plywood. Both are wood. Both require the same adhesives...and both have the same failure rates (ie the 'rotten plywood' comment above). The next issue would be height variation. I would expect a transition. Even a small one. And the reason: the townhouse subfloors were BUILT to accommodate cork glue down tiles (probably 4mm) in the kitchen and then another floor in the living space (???original floor???). And this BUILT IN floor height variation will never go away. Not unless you go back in time and make all of your decisions based on the inclusion of the hardwood running into the kitchen. I personally would find out if the engineered hardwood (with the 4mm wear layer) can be FLOATED - most are allowed to float...but not all so it is best to be super prepared. If it can be, your situation has been solved....remove the old vinyl/cork and FLOAT the new hardwood in the kitchen. A thin sheet of plastic will be laid down over the concrete and the wood will be floated over top. You will have a small transition ANYWAY (floor height variation = transition) so you might as well change the type of install to MATCH your slab = floating hardwood = MOST APPROPRIATE form of wood flooring install over slab. Also be aware that the finish might have a slight colour/gloss variation. Again, that's where a well prepared transition strip/area can be SUPER helpful in hiding these slight variations.