Subfloor thickness for 3/4" wood floor question

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I want to lay down 3/4" hardwood floor in my livingroom, after removing the 5/8" particle board underlayment which was used for carpeting, Im left with 1/2" plywood subfloor.
My question, Is the 1/2" plywood subfloor thick enough to lay the 3/4" wood floor on?
The floor will run in the opposite direction of the joists for strengh.
Advice appreciated, thanks in advance.
Gil
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Gil,
Are you sure you only have a 1/2" subfloor? That just seems too thin - the floors would give when you walk on them. Plus, I wonder if it meets building code.
To answer your question, I would recommend putting down another layer of plywood - you must have a smooth surface with no hills and valleys and gaps for the hardwood to sit on. Most underlay will require at least a layer of luan on top. In your case, I'm thinking you'll need a 1/2" luan or other similar smooth surface layer.
I did my kitchen floor a few years ago. I had a 3/4" tongue and groove underlay that was pretty rough. I put 1/4" luan on top of that, then put 6 mil poly over that as a vapor barrier. Then the 3/4" solid hardwood.
When you put the hardwood down, don't scrimp on the installation. Rent one of those big hoss pneumatic staplers. It comes with a big mallet to knock the boards tight and set the staple. Whack the crap out of the stapler with that mallet. I have 3 or 4 places where I didn't get the boards tight because I wasn't paying attention and hit it too lightly. It's not real noticeable except during those real dry winter days.
Bob

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Bob, thanks for the advice.
It is 1/2" subflooring. I spoke with an installer today, his logic was... "if there was 5/8" particle board underlayment on top of the 1/2" subfloor, the 3/4" hardwood T&G on top of the 1/2" subfloor will be even stronger than before and you even gain an extra 1/8 of an inch", but I still like to hear oppinions from others that have done the job.
No doubt the thicker the subflooring, the better, but I dont want to overkill if I dont have to.
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3/4" of hardwood T&G flooring is plenty strong enough without any underlayment.
make sure the 1/2" ply that is there has a nice smooth level surface, or it will make a bunch more work for you during installing and finishing of the flooring, and may contribute to a squeaky floor problem later on.
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nails. The half-inch plywood wasn't thick enough to hold the nails. I was nailing three-quarter inch thick oak strips. This was in a kitchen with a lot of foot traffic. The flooring became loose in places after about six months, so I pulled it up and put down another layer of half-inch plywood. This was really truly a pain in the ass. Put something more substantial under that hardwood. You can go to www.nofma.org , the wood flooring org. for lots of good info.
good luck das
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Das...I forgot to mention the installer i spoke with recommended nailing through the joists when possible over the 1/2".
Im just trying to get the most information I can before getting started, and I have noticed in all cases at least 3/4" subfloor is recommended.
Thanks for the info,
Gil
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What 3/4" flooting are you putting down? If you ae workign with oak there are a few grades. Length is part of the grade. If you install a lot of short length boards then the 1/2" is going to be a light. If you are nailing over trusses the floor may be more even than nailing over joists. Especially if the joists have a lot of crown. I recall years ago th ebuilders did 1/2" plywood all over the house and the oak went over that. The carpet areas, the vinyl and tile floors were doubled up. When I did my floors I was aware of at least three grades. Select, common and cabin. Select is supposed to be pretty knot free which it was. The other grades have more knots and maybe had more short pieces. It appears that my recollection of cabin grade may be left over from Color Tile days where the parquet floors had a cabin grade. http://www.nofma.org/gradingrules1.htm
As the other person mentioned the floor manufacturers web site it a great place for reference materials.

Jim B.
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there are a few grades. Length is part of the grade. If you install a lot of short length boards then the 1/2" is going to be a light. If you are nailing over trusses the floor may be more even than nailing over joists. Especially if the joists have a lot of crown. I recall years ago th ebuilders did 1/2" plywood all over the house and the oak went over that. The carpet areas, the vinyl and tile floors were doubled up. When I did my floors I was aware of at least three grades. Select, common and cabin. Select is supposed to be pretty knot free which it was. The other grades have more knots and maybe had more short pieces. It appears that my recollection of cabin grade may be left over from Color Tile days where the parquet floors had a cabin grade<<<<<<<<<<<<
Jim....so you're saying if I were to use "select" oak which you get longer planks and lay it over the 1/2" subfloor (providing that I nail it through the joists as much as possible) I should be ok?
I am worried about pieces that will end between the joists will have movement and eventually squeak or worse become loose.
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gil wrote:

Good advice, but watch out for the nails holding the plywood to the joists.
Barry
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I've installed oak flooring with a manual floor nailer, but much prefer an air driven one. Another useful tip mentioned earlier by other responder is the quality of the flooring. I am not sure if wood is graded solely on its appearance, but also for true and square of the planking. While my pre-finished cheap stuff did not have many knots, a lot of pieces in the package were warped or bowed. For a good work out, try forcing curved short lengths of oak planking onto the tongues the corresponding strips already nailed to the floor. One quickly realizes just how rigid 3/4" oak planking can be. In short, be sure that the planking is reasonably straight and level or you will wish that you'd never begun the project. Another concern, that is hard avoid when buying cartons of pre-finished wood, is getting packages consisting of just short lengths of flooring. Sometimes a package will contain nothing but cutoffs that are all neatly stacked in the box by the manufacturer. Granted a few short pieces are fine, but boxes full make for a choppy looking floor.

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If I'm correct in the old days floors were built with 1/2 inch running one way and 5/8 inch on top of that in the oppisite direction. Now days everything is 3/4 inch t&g. Like everybody else here, my advice is to go with another layer of at least 5/8 inch ply and run the long side oppsite of the 1/2 inch if possible. Also, you may want to consider using a porta nailer manual nailer. Having to manually hit the plunger a couple of times not only sets the nails but does a nice job of tightening up the joints. Good Luck.
BG

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How much force is needed to use a porta manual nailer? Think it could be used from a sitting position? (e.g.. a wheelchair) From a sitting position, it would be all arm motion hitting the nailer without any body motion to add to the force hitting the nailer.
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From my experience (used one twice), you pretty much have to operate the manual nailer from a bent over position while standing. One hand is used to hold the nailer against the tongue (by way of an extended handle at the top of the nailer) and the other hand, of course, is needed to really swing the mallet. I suspect that this would be difficult from a seated position and the wheelchair frame could get in the way. However, this might be possible if one were to use an air driven nailer because less force is involved with the mallet hand. In either case, one would need an assistant in order to get each plank fitted tightly over the tongue of a corresponding plank.
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TEF wrote:

Air powered flooring nailers aren't much different. The main difference is the hammer force. The air unit still needs a decent shot, as the striking motion helps set the board. Air helps the nail drive be more consistent.
I have a Porta-nails air unit and wouldn't trade it for the world.
Barry
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What about from an angle leaning over the side of the wheelchair? Don't forget, from a sitting position, I'm close to a foot shorter than someone who is standing. As well, I'm fully capable of leaning over far enough to pick something up from the floor and I have a great deal of upper body strength, so leaning over if needed isn't a problem. I guess I'm just theorizing at this point. I'd never know for sure until I actually get my hands on a porta-nailer and actually try it out.
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In my first response on the subject of operating a manual nailer from a wheelchair, I said that "I SUSPECT that this would be difficult from a seated position". I wasn't ruling out the possibility. As the old saying goes about "the proof of the pudding", so you could easily prove me wrong and, indeed, I hope you do. A lot of respondents in this thread like the manual nailers (vice the air driven ones), so perhaps I am wrong about them. However, my recall of these was that one really had to pound on them in order to tighten the floor and drive the nail. Moreover, when I watch flooring being installed on TV (in one of those DIY-type shows), the installers always seem to use air nailers.
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TEF wrote:

I suspect those folks haven't tried the air version. <G>
Barry
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used my left foot to hold the wood snug to the already nailed flooring. Balancing on both legs, an arm to hold the pneumatic nailer and another with a bunch of chest thrown in to swing the mallet firmly to set the wood tight and actuate the nailer. It took a good while to do the floor as it was. My intial set of the wood consisted of a quick quality control look and then placement of the wood. A firm tap while the foot was resting heavily on the wood to place it fairly tight. I might have to reach 3 feet to the left to swing the mallet to set the end tongue tight. My dad did a series of wedges when we fixed some flooring in our old house. We nailed a scrap 2x4 on the floor. We drove a wedge of scrap flooring against the bowing floor and the 2x4 to force the bow out.
I guess I am saying it was a full body experience. If you are used to working in a chair then you probably know good tricks to work with what you have. I sometimes do not work smart. ;-(
Jim B.
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I suspect that everything you've said is probably correct. I just happen to be one of those people that likes to do everything myself and don't like to ask for help (unless it's asking a good looking woman to reach something for me in the grocery store). I'm guessing that I can operate a porta-nailer satisfactorily, but that I'll have a problem keeping the wood in place while I'm nailing it down. I seem to remember a show on TV once where they were using a type of ratcheting web clamp to keep the wood butted up tight while it was being nailed down. If I ever do a floor, I'll probably end up getting some buddies to help me and then spring for some beer after that.
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Upscale wrote:

Maybe some kind of attachment to the chair to work as a "third hand", use the inertia of yourself in the chair to apply force, and then use the brake on the chair to hold things together while you nail?
--
--John
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