I bought nearly 2000sf of floating click-n-lock floor. It came in 3 sizes, 4ft, ~3ft, 18" and 1ft lengths. We purchased very good underlayment at $38 per 100 sf. After the first 1000sf I stopped installing and called the manufacturer. Every step squeaked. I could even hear my 15lb shiz-tzu squeak the floor. Previously I had Kahrs floating floor and it did not squeak; but it was installed in 2001 with 8" wide 8 foot length pieces that were glued together(not to the concrete slab). I liked it but a broken fridge line ruined it so we had to replace the floor. Since it didn't squeak I didn't expect this new floor to. The manufacturer said it was defective wood, refunded me all the money for the wood, took back the unopened boxes and told me to throw out the 1000ft I had laid. I don't believe it is defective. I think this is what you get with this stuff. So after consultation, we decided to glue our floor down. We pulled up the floated floor, bought some more wood and had a professional re-install(with very good adhesive/glue). It doesn't squeak but we don't have that soft feel of floating floor that I liked. Also, I believe they used a urethane adhesive and it did not smell at all. Absolutely no glue smell. If you don't like the creaking, be careful with floating floor.

Is there a reason nail down is preferred on floors with a wood subfloor? The flooring subcontractor will do whatever method we want, but he advised against nailing down bamboo. He said he occasionally sees dimpling of the nails visible on the surface of the wood and prefers glue or floating.

If these are Torlys engineered click together floors (with the HDF core) you are going to have concerns gluing down. Only if this is SOLID CORE hardwood engineered flooring can you look to glue down. The problem: HDF moves A LOT. It LOVES to expand and contract (as much as 1" over 25 linear feet....that's a LOT). The hardwood on top DOES NOT! If you glue down the HDF core product, you restrict a DYNAMIC plank. That plank will have problems. It will eventually rip itself away from the adhesive....the expansion forces will break the glue bond. And the glue is NOT grabbing the HDF....it is grabbing the CORK UNDERLAY. The cork underlay is the weakest part of the plank. Go ahead and pick at it with your nail. It crumbles after a few strokes. That's what the glue will be grabbing. It would only take one full "heating-cooling" cycle (winter-summer) for the bond to break. If you have installed floating floors with T-moldings before and "had no problems with it" then I suggest you keep going with that successful approach. Remember: "If it ain't broke; don't fix it," is something we all live by in the building industry.

Oh dear. Noise abatement requirements with hard surface flooring over light weight concrete (aka "gypcrete"). And you only have enough room for 6mm worth of acoustic insulation. Hmmmm. You are getting into expensive territory. First check what is ALLOWED by the HOA/Condo board. They will have ratings that will tell you what you have to MEET or exceed with hard coverings. Secondly check to see if the acoustic glue underlayments will even grab gypcrete. Most things HATE gypcrete. I mean HATE. There are many high-quality glues that do NOT grab gypcrete. And the one's that do, can be nasty. But don't worry. Being in California means you can't purchase anything that violates CARB compliance - unless you order it over the internet (ahem...best to stick with brick and mortar point of purchase for stuff like this). And just for fun, not all wood floors can be floated and not all can be glued. And not all glues grab gypcrete...see where we are going here? And then there is the noise abatement that MUST be addressed BEFORE you go any further. Without those numbers, you are flying blind and so are we. In the cork industry, I NEVER got my 6mm cork underlay to pass a SoCal condo boards requirements. My customers ALWAYS had to go 12mm with a wood floor (of any kind). You can get some decent sound reduction with mass loaded vinyl. But it is expensive. It is very thin and very expensive. And vinyl does NOT like sitting underneath wood. But it depends on the mass loaded vinyl product. And QuietWalk Plus is a product that is relatively thin and yet has some of the same acoustic insulation as 12mm cork underlay. It will save you the height at least. It too is not cheap. https://www.mpglobalproducts.com/flooring-underlayment/products/quietwalk-plus/sound-rating/