The plywood over the cork is needed for a NAIL DOWN hardwood. Nail down is the CHEAPEST method for installing any form of hardwood. Glue down hardwood is the most expensive. It is also the BEST for sound. So....the sound deadening for the area REQUIRES the plywood. You can't get around that. The cork is required so you can't get around that. You cannot nail INTO cork. You must glue to cork. That is the only option. So... you are adding the plywood for the sound requirements AND for the installation options. With all those layers, the labour costs are bang on. If you estimate $2/sf for EACH LAYER of prep....you come up with $8/sf without MUCH EFFORT. The glue for the cork to concrete = only option. The glue for the PLYWOOD onto the cork = only option. We call this a double stick. If you glue the hardwood to the plywood you would have a TRIPLE stick. This is the MOST IMPRESSIVE option out there. It is also the MOST expensive option. You can nail into the plywood = no problem SO LONG AS the plywood is THICKER than the nail shanks. You do NOT want nails reaching into the cork layer. If the cork layer is pierced by nails, you start to LOSE the acoustic properties of the installation. If you think of each nail as a small telephone wire (ahem...metal TRANSMITS NOISE REALLY WELL) that is transmitting noise from your space to someone else's...and vice verse, you get the idea. One nail is no big deal. A floor with 10,000 nails = 10,000 telephone wires transmitting noise THROUGH the cork insulation and into your space. This is a HUGE deal. Again, the nail down install into the plywood is NOT an issue so long as the nail shank does NOT reach the cork. That means you want a plywood layer that is roughly 1/2". And with cork costs that are MORE EXPENSIVE than the plywood, you must be purchasing 1/2" cork. The cost of 1/4" cork should be the SAME as 1/2" plywood. Check your thicknesses so that you can feel confident that the right thicknesses are being used for the type of install that is about to occur. Most of LA likes to see 1/2" cork. I hope this helps.

Thanks all. We removed the floor. Unfortunately as expected, that exposed more of a mess. Luckily, no "damage" to subfloor per say, but it looked like the previous folks who installed the floor used leveling "float" on pretty much the entire 700 sqft and in some place as thick as almost 1.5 inches. This made it very difficult to remove the layers of flooring (combination of engineered hardwood glued down and some solid wood nailed down to plywood, which was glued and nailed down to "leveling float", which was poured over OSB subfloor). The demo guy tried to get to the OSB subfloor as best he could but he stopped after 2 days of demo and when the OSB was starting to get damaged as it came up with some of the float. We have now moved on to filling the 3 very low areas with some plywood and then pouring self leveling float over the entire floor to try to fill in all to "holes" that were created by trying to pull up the previous float. I guess I am officially welcomed to home ownership.

Did you end up going with these floors, and if so, are you happy with them and do you have any pictures? We just chose these for our bedeoom, but can only find the pictures on the manufacturer’s site.

In *theory you can lay a new wood floor over an old one....but you must be 100% sure the old floor is flat (no humps, bumps or valleys) and 100% adhered to the concrete. If your installer has already told you there are voids then you are already on the back foot. You have to fix that first = glue added and then allowed to cure. Then you have to make sure that floor is flat. That probably means some sanding (which you are trying to avoid because you want to put wood on wood) and possibly some 'filling'. If you have to do all that, it is probably better to rip out that old wood (I'm assuming you have already found out it cannot be refinished?????) and start again. Besides, you would have to rehang the door and you would have to build one HECK of threshold transition to step up that 1/2" - 3/4"! That's a TOTAL bummer! Believe me!