I want to install a 3/4" solid hardwood floor on concrete floors in a high rise condo. The association says you can have either the wood flooring on cork or plywood or both.
I believe for cost for plywood would be cheaper because of the adhesive costs asociated with cork. Is it best to nail or screw the plywood to the concrete? Can you use 5/8 inch plywood instead of 3/4"? (I am concerned about the total finished height)
If I elect do do both cork and plywood can I just lay the 1/4" cork down and then the plywood and then screw or nail both together? or do I have to glue the cork first? Lastly since is is a high rise is there any concrete moisture concerns I have to think about?...thanks for the help

Sounds like your looking at a naildown installation ( 3/4 plank or strip is usually naildown ).The cork that the Assoc. is talking about is for floating hardwood, ( 3/4 is not floated )
So you would want to install a plywood subfloor, ( minimum 5/8" , I prefer 3/4"). IMO I would consider installing a floating subfloor. Cutting the plywood into 4' X18" strips, stagger the seams, & install perpendicular to the direction of the hardwood. If you like , you CAN use
cork as well, for sound barrier. I would loose lay the cork over the top of the subfloor. You can also loose lay Insulayment over the subfloor, great product, costs less than cork.

Since this is a high rise you shouldn't have to worry about substrate moisture, ( as long as your not using leveling compounds, and nothings leaking). And I assume the substrate doesn't have radiant heating. You do want to keep the RH in the home within Manuf. range, and acclimate the wood. I would check the moisture content of the plywood subfloor, in relation to the hardwood before installation.

Thanks for the reply..I need a little more clarification.
The building association for the condo high rise states...."All wood parquet and ceramic tiles, or the like shall be installed over either 1/2" plywood, or 1/8 corkment properly installed"
Question...If it is Ok to use 5/8" minumum but preferably 3/4" for the plywood subfloor why is it Not OK to use 1/2" plywood....what does the extra inches give you if it is going to be nailed anyway?
Question....If Insulayment or cork is used for a sound barrier is it for the benefit of people below you or does it help with your sound barrier problems in your own unit?
Question....If Insulayment or cork is used, then what is the height of the Insulayment product ? Can you use 1/8" cork ( does it come that way)
and lastly ....most important ....
Can Either Product be installed by just laying it down and then nailing under the plywood?
Thanks again.

1) The 5/8" minimum thickness plywood is necessary if you want to install a 3/4" naildown hardwood floor. The planks are installed by blindnailing staples or cleats through the crease at the top of the tongue, into the plywood. 5/8" thickness plywood is nesessary for desired "fastener grab" to install the planks.
2) Insulayment or cork performs as a sound barrier to both the unit below and your unit. In addition it adds insulation qualities to your unit. Usually the association has a decibal rating spec they adhere to. Before you do anything, be safe, and run it by them.
3)Insulayment is a nominal 3/16" thickness. Yes, cork comes in 1/8", used for many installs. Again, run anything past the Assoc. Get it in writing. I recently completed an install that the Assoc. required Protectowrap Whisper Mat HW , no budging.
4) I typically use Insulayment, and it is designed to loose lay on top of the plywood. I havent used cork in the past, although I know it is typically installed over the plywood. I'm not sure if under the plywood is an option , or why you would want to install it under the plywood. Are you trying to remedy a slab out of spec? The majority of highrise condos out here ,the slabs are out of flatness spec. , but we float them with self leveler.

Thanks again for the reply....At this moment I do not know if I have a slab out of spec. I will be pulling the carpet up next week.
I did not want to lay the Insulayment or cork under the plywood...I just thought that was the way to do it. Now you are saying the right way is to nail down the plywood. ( i'll use the 3/4 plywood for a better install) .. then lay the sound barrier ( I think I will use Insulayment) and then staple or cleat the 3/4" solid hardwood over it...right? I didn't know that was the way it was done.
Question ...can I appraoch a floating floor the same way? is it cheaper then the nail down floor? I just thought nail down was a better job
Question...if there is a problem with the concrete slab out of spec....what is the best way tp deal with that? will shims work or do I have to use some sort of leveling compound?
Question...as far as the RH is concerned ...what are the requirements for 3/4" solid red oak 3' planks? I live in Chicago. I know you have to acclimate the wood in the condo for a few days before install but does it have to be at a certain humidity?
I appreciate all of your help

1) I didnt say the right way is to nail down the plywood. I suggested that I would consider installing the plywood as a floating system, ( being you have neighbors under you). Floating the plywood is also a desired alternative to many installers and installations. You can also fasten the plywood down as well.
2) The Insulayment or cork is loose laid on top of the plywood. The hardwood is installed directly over the top of the Insulayment or cork.
3) A naildown floor is not a better job than a floating floor. It's a different type of installation, a different feel when walking on it, & a different product. Most engineered hardwoods can be floated ( check with the manuf.), solid hardwoods typically require a naildown installation.
4) If you decide to do a floating floor, you would be selecting a different product than the 3/4" solid you mentioned. Choosing a product for a floating installation could save a bunch of money. You would be able to loose lay the sound deadener/underlayment directly over the concrete and install the floor. Savings could be significant on material & labor. Ofcoarse you can make up that difference in your product selection.
5) Re: Slab out of spec. Cross that road if necessary, hopefully it's not out of spec.
No shims. I's a combination of grinding & leveling compound, depending on the situation.
6) Hardwood is acclimated, under normal living conditions, with the heat or HVAC running. Acclimation is approx. 1 week , BUT depends on the environment, the product, and the MC of the product. Check with the specific Manuf. on the Rh they suggest for their product.

I would suggest looking at an engineered floor that can be glued directly to the slab or floated. You would need to verify that the slab is not actually gypcrete if you were gluing it down. Floating would be my first recommendation using something thick like 1/2 to 5/8.

If you want a "solid" there are 5/16" or 3/8" solids that can also be glued down directly without having to deal with a subfloor.

Ok..Floating ....help me out here.
When I first looked into hardwood floors for the condo I knew about solid hardwood floors because I currently have that in my home. 3/4" Solid oak planks ..nailed down..custom stain.
Then I heard about 1/2" to 5/8 "Engineeeed floors ...floated .. pre-stained. Was told you get more of a squishy feeling when walking on that type of floor but you save some height issues of finished product Cork is expensive in this app, becausr of the adhesive costs.
I was then told that although solid wood material have come down over the last couple of years engineered material has not. I was also told that an Engineered floor would cost depending on the brand and there are many( need to make sure you get a good quality manufacturer not a cheap import) cost range around $5-$7 sq ft cost for good material alone and then with install with corf etc..$10-$12sq ft installed.
I know that solid wood (select or better) runs around $2 st ft. Nailed down with custom stain running around $8 on vaious quotes even with placed in position cork.
What am I missing here. Even if you could get a floating for the same price ...why is it more preferred. Also if it is Gypcrete what does that mean? Please advise!!!

You are forgetting the cost of a nailing base ( plywood ) if you use a solid nailed down floor. That can easily add $2.00 a ft. to the job. To install a solid 3/4" floor in your condo, you'll need 3/4" plywood nailing base plus the 3/4" flooring. And perhaps some cork or insulayment to diffuse sound. You could end up being 1.75" off the subfloor, which is most likely a type of light weight concrete like Gypcrete. One usually cannot successfully attach flooring or wood to Gypcrete so it's recommended to "float" the plywood nailing base.

Now an engineered floating floor may cost more in flooring materials but there is way less labor involved than nailing down an unfinished solid. For me to supply all the materials and labor to float a subfloor in a high rise, nail down unfinished, then sand, stain and finish it, I'd have to get at least $16.00 a ft. A floating engineered can be installed for around 10 to 12, including materials. Plus, it will be lower in height and not interfere with doors and appliances.

"Then I heard about 1/2" to 5/8 "Engineeeed floors ...floated .. pre-stained. Was told you get more of a squishy feeling when walking on that type of floor"

A good quality, thick engineered wood floor properly installed over a flat substrate and using a high quality underlayment like Sound Solutions padding will not feel squishy. Most people have never walked on an installation like I described because the majority of jobs I see people don't take the pains necessary to provide a fairly solid feel. I have personally installed enough jobs to be able to say that.

If you have gypcrete , one cannot glue directly over that without using a sealer to harden it first. Floating is much preferred over gypcrete in my humble opinion.

Jerry...you said
"A good quality, thick engineered wood floor properly installed over a flat substrate and using a high quality underlayment like Sound Solutions padding will not feel squishy. Most people have never walked on an installation like I described because the majority of jobs I see people don't take the pains necessary to provide a fairly solid feel. I have personally installed enough jobs to be able to say that."
Question...What pains can someone take to make sure the padding does not feel squishy if you cannot use any underlayment other than cork? ( those are the Condo rules) Thickness of cork you would recommend?
Question.....What constitutes a good quality thick engineered floor? Are the wider the boards less solid feeling than thinner ones?

If you are contemplating a floating installation and desire to have a pretty solid feeling floor the issue of substrate flatness is critical and often overlooked by installers and DIY'ers alike. The flatter you get it the happier one will be. Cannot stress that enough.

The wood itself (imo) should be a good quality engineered product a minimum of 1/2" thick and I personally prefer a joinery that uses glue in the joints like Andersen Virginia Vintage for example. The underlayment carries equal importance and I have tried many different types, including QuietWalk, FloorMuffler, etc. My personal preference is the Sound Solution padding. It's very heavy and dense..... weighs 16 lbs per 100sq ft. as opposed to 1 lb. per 100sq ft for normal foam padding.

I would go back to the Condo association and clarify if cork is required "if" one is floating a floor. It could be they require cork if one is gluing down or fastening down a floor. I have never used cork yet to know how good it works.

As far as "Flatness" is concerned how bad does it have to be before you do something about it? How can you tell? At this poinyt I do not know because I will be pulling up the carpet off the concrete floor next week.
Aren't all concrete floors uneven to a degree?
What steps do I need to take to see if the floor is uneven...take a level?
If it is bad do you use a Self leveling compound.? Tanks