Hi all,

I'm a new homeowner, and I'd like to install hardwood floors in various rooms in my home. The first project I will tackle is a 100 sq. ft. family room, it seems easy enough. I'm in Florida, so I have no basement, this will be on grade. I've read all the tutorials and even looked at some Youtube videos. My problem is what to do about installing a subfloor. All of the instructions I find are for a basement. I guess my specific questions are what is the best way to attach the subfloor to the concrete? With glue, or nails or screws? And where should I lay the moisture barrier. Also, I'm having trouble with exactly what is a "sleeper" floor. Some the sites I read said to use 2x4's or 1x2's spaced apart, some said to use sheets of plywood. So if someone could give me a little more clarification that would help alot.

I would like to say I'm not interested in floating a floor (with Lock and Fold or something like that), I already have one in the dining room and I don't like it too much, I don't like the "give" in it. And alot of articles I read have scared me away from gluing an engineered floor, with the messiness and all that like the article at hardwoodinstaller said. So I guess bottom line is I would like someone to clear up the subfloor over concrete on grade question. Thanks.

Welcome arctanx ..
First thing you want to do is check the floor for flatness ...Must be no more then 1/8 " in 6 ' or 3/16 " in 10 ' Also do a Polly film test using a 6 mil polly film Tape a one-foot square of 6 mil clear polyethylene film to the slab, sealing all edges with plastic moisture resistant tape. If, after 24
hours, there is no “clouding” or drops of moisture on the underside of the film, the slab can be considered dry enough to install wood floors ..If there is signs of moisture a Calcium Chloride Test must be done .. You can also do a floating nail down .. glue the 6 mil polly to the floor with a water proof adhesive , let it ride up the wall at least 2 " .. Cut some good quality 3/4 " plywood into 2 x 8 piesce > cut 1/4 " deep lines across the back of the ply every foot to allow for expansion and contraction .. 1/2 " short of all walls .. stagger the sheets .. lay down 15 lb felt , and nail the wood to the ply ..

Thanks for the reply.

Now that 3/4" plywood you're talking about, how do I attach to the concrete? With nails, screws, or glue? Or does it just float?
Thanks.

Just lat it lay there arctanx .. It is a floating nail down .. Make sure your plywood and flooring are within 2 - 4 % of each other .. RH sould be at 35 - 50 % at a tempature of 68 to 70 degrees ..

Nick, why wouldn't you tapcon the plywood down? I am about to do this on a concrete slab at grade.

Also can you do it with 5/8 inch? I was going to tapcon the plywood.. i have some slight depressions in spots... I am talking 1/8" or so.. i thought by tapconning the plywood...it would make for a squeak free floor that i could nail to..

You can nail it to the floor if you want .. Tapcons aren't cheap .. You will need a lot .. I would flash any low spots first , and make sure what ever you use is flush to the sub floor ..

I was going to use tapcons, because i don't have a gun that will nail to concrete..

what should i flash with? floor leveling material?

[quote="Nick"]You can nail it to the floor if you want .. Tapcons aren't cheap .. You will need a lot .. I would flash any low spots first , and make sure what ever you use is flush to the sub floor ..[/quote

I have about 800 sq ft to do... it might be faster and more economical to buy a gun ..i have a compressor.. the cost of the tapcons might outweight the cost of nails and the gun.. What do you think?

You can rent a gun , but those nails are not cheap either .. You can use a good self leveling cement compound to flatten the floor .. You still want to put at least a 6 mil Polly film on the floor after you flash it , and let it ride up the wall two inches ..

As soon as you start fastening the plywood down with 1 fastener every sq.ft. that is 32 holes in your poly moisture barrier, that is now no longer a moisture barrier, but just a waste of time and money.

Asphalt mastic, full spread on the concrete. A layer of 15 or 30-lb asphalt impregnated felt. another coating of asphalt mastic and another layer of asphalt felt laid the opposite direction of the one under it, overlapping the seams 4" Now, lay out your poly plastic moisture barrier. When you fasten it down, the asphalt seals the fastener penetration.

Your in Florida The asphalt is mandatory!

How about sealing the concrete, full mastic, one one asphalt, then barrier.

Someone else in this subdivision had her floors put in 20 years ago...and I somehow doubt they went to that length.

I like your idea about the full mastic and asphalt.

What length staple would use use to drive 5/8 inch solid oak into 5/8 plywood? on the angle do you have room to get 1 1/2 inch?

Thanks for your advice.

5/8 ply subfloor, is too thin to do a nail down. You will need a ¾" base and 1½" fasteners, so they don't penetrate the moisture barrier from blowing through the subfloor.

The floating subfloor, is really the best way to go. Roll out your felt then poly. The felt keeps the plastic from rubbing and wearing through. Then cut 4x8 sheets of ¾ plywood, into 2x8 or 16"x8 planks and lay them the opposite direction of the finished flooring, staggering the end joints. Then nail your flooring to the floating plywood planks, going across them, the opposite direction.

Do you cut expansion lines across the back of the plywood AustinFloorguy ?

I am going to do two layers of felt , moisture barrier.. then lay the plywood... i will tapcon the plywood where necessary to make sure it is flat on the floor... i think i will be ok with 5/8 because the solid oak is only 5/8. i am afraid if i float the plywood it won't be solid in some places. I just don't want any squeaks... that was my problem originally with the floating floor

Good luck with that!

I feel your headed down the road to disaster, because your fasteners for the wood flooring are going to be too long, if you use 5/8, but do what you want. It is your money after all, and not mine.