Hello, I'm new here and had a few questions I did not see answered when I searched the site.
I am going to install a floating subfloor over concrete. The plywood I will use is 3/8" crossed over each in a perpendicular pattern stapled together using 1/4" crown 5/8" length staples. This will be installed over the vynil flooring that is already down on top of the concrete. I am going to use a 6mil vapor barrier over the vynil then install the plywood then put 15# felt ontop of the plywood then 3/4" solid wood, hickory. I know this needs to be level to 1/8" or 3/16" over ten feet. My questions are:
1. How much give/flex will this system have? Will a 1/16"-1/8" or even 3/16" give/flex be bad for the solid wood.

2. If there is a little give will the solid wood help to solidify the flooring?

3. When installing the plywood through a doorway, from bedroom to closet, if there is not a good way to attach the plywood sheets together is it ok for them to be seperate? What I mean is they are not attached, but have the normal 1/8" expansion gap between each other.

4. If when down the plywood has a crown to it, will the solid wood flatten the crowning? Should I use tapcon screws to attach the crowned section to the concrete?
Thanks for any help with understanding this flooring system.mi just want to cover all my bases before installing this flooring.

Why are you floating it? 3/8" ply does not seem like very much material to nail to, what size cleat would you use for that?

When I did mine concrete Din i went with 3/4 T&G ply and did Tapcons to attach it to the slab.

The two layers of 3/8" plywood over the concrete equals 3/4" plywood. I'm just making a large sheet of 3/4" plywood that is the shape of the room.
I decided to float the subfloor because I didn't want to have to worry about a liquid vapor barrier for under the 3/4" plywood that would have to be screwed into the concrete. This also seemed like the easiest and most forgiving subfloor to flatten.
I used an 1 3/4" cleat.
I don't need help anymore I just finished the rooms. They are very solid feeling and turned out great!

My mistake, i misunderstood the overlapping 3/8. Glad all went well!

I hope you didn't tapcon any parts of the floating plywood subfloor. That could cause some movement issues.
Good job other wise. Lets see some pics.

No I did not use the tapcon. I let the wood flooring attach the closet plywood to the room plywood.
Here are a few pictures of the rooms I put the flooring in. The lighting is a little different from room to room, so the colors might be a little different.
Here are a links to my flooring. I could not figure out how to post images.

http://stultis.deviantart.com/art/Wood- ... -612467048

http://stultis.deviantart.com/art/Hard- ... -612467549

http://stultis.deviantart.com/art/Hard- ... -612467894

http://stultis.deviantart.com/art/Hard- ... -612468074

I had done a stained concrete floor for the rest of the house, so I need to make transitions from the wood flooring to the concrete. The height difference is 1 1/2". I think it all turned out pretty good.

Half of my house is on a slab (split level) and I did 6 mil plastic then 3/4" Sturd i floor and tapcon'd it to the slab. I ran a bead of silicon in each hole before setting the tapcon. This was well over a year ago and I've had zero problems.

I like the idea of a floating subfloor, since I had height issues I ended up going with 3/8 solid oak for this part of the house. Being so thin I was worried about bounce, warping, etc..