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lombardguy

Can 3/4' Oak Hardwood floor be put over OSB?

18 years ago

Hello. I am hoping there will be experts in this forum to help me. It seems like every flooring store I go to I get a different answer... Three stores have said that you cant put it over OSB, two have said there shouldn't be any problem and one said to glue it... All of the stores answer with complete conviction and insist they are correct.

Can anyone here please guide me on this topic. I dont want to end up with loose boards in 5-10 years. I would have this professionally installed and I am sure it would come with some type of installation guarantee but I dont want the aggravation down the road from an improper install.

Your response are appreciated.

Comments (52)

  • 17 years ago

    OSB can be ok if it has a rating of ps-2-92. Others won't work as when you nail if will shatter the osb and it won't hold tight. This is from the Armstrong or Bruce website. If you don't know I wouldn't try it.

  • 17 years ago

    It is GOING to be OK to install over OSB, because OSB is becoming the subfloor of choice for builders. They are, of course, using OSB with the proper rating for use as a subfloor.

    What others have said about preparing the surface is good advice.

    Don't expect anything more than the standard one year warranty on workmanship from anyone; it's unrealistic to expect a tradesperson to warrant an installation or provide free service on any installed product after that.

    All naildown wood flooring will loosen some over time. The worst problems are with floors that are installed over "wet" subfloors. Be absolutely sure that the OSB is dried in enough to proceed with a wood floor installation. The flooring and the subfloor needs to be to within 4% moisture content of each other. The use of a moisture retarder between the OSB and the flooring is also good advice. Be sure the retarder is lapped at least 4".

    Of course, floating wood floors avoid many of the potential pitfalls with a real solid hardwood floor...but they are not real solid hardwood floors.

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  • 17 years ago

    I WOULD NOT install hardwood directly over OSB. Main concern is nails/staples coming loose from the OSB over time. OSB is fine as a subfloor structurally, but IMO, it won't hold a nail or staple as well as spruce plywood. Especially if you are using a stapler to install the wood.

    I would overlay your OSB sub with 3/8" spruce plywood and screw it down. First, I would ensure the OSB is securely fastened down by screwing it into the joists with screws and then overlaying the spruce (make sure to tile the 4x8's) and fasten again with screws.

    You'll have a nice, even and clean surface to install onto, well worth the effort, IMO.

  • 17 years ago

    We had major headaches getting wood floors installed upstairs in our house. The subfloor was OSB. The flooring company said the subfloor was fine but after 4 tries they finally screwed down 1/4 inch luan & laid the floor on top of it. Cost a bit more but I wanted to be sure there wouldn't be issues down the road.

  • 17 years ago

    We are also planning 3/4" oak hardwood. Can someone please explain what OSB is? Is it a type of subfloor? I have no idea what our subfloor is made of (house is about 35 years old).

  • 17 years ago

    Oriented Strand Board.
    Am improvement over chip/flake boards, but still not as good at holding nails as plywood (or even better is actual wood).

  • 17 years ago

    Thanks! Sounds like plywood/wood is the best subfloor then?

    I'm crossing my fingers that's what I have for my 35-year old subfloors.

  • 17 years ago

    I'm going to bump this old thread back up.....

    Does Advantech subfloor take nails better than OSB? or not?

  • 17 years ago

    I don't know about holding nails better, probably does, but is a far superior product than OSB. I have installed many jobs over AdvanTech with nary a problem. I've not had any problems with 3/4 OSB either. Recently I was in 2 houses I installed hardwood over 3/4 OSB about 9 years ago...I was amazed at how good they looked, no squeaks or gapping either. I use staples instead of cleats.

  • 17 years ago

    it all depends on the grade and quality of Oriented Strand Boars (OSB) panels !

    There is some OSB (Advantec for example), which is actually a better product than plywood.

    The right product for the right application.

    Boxers is completely correct.

    Check the grade !

  • 17 years ago

    thanks for the input.

    we're building right now and using Advantec with 3/4" red oak nailed over it.

    sounds like it is at least equal to plywood as far as holding a wood floor.

    thanks again. :)

  • 17 years ago

    Staples!!!!!

    Cleats don't hold well in either OSB & Advantec

  • 17 years ago

    thanks. I'll stress, staples.

  • 17 years ago

    Appreciate reading the comments on this thread. We're looking at putting down 3/4" hardwood soon; area will include familyroom/livingroom/kitchen. A couple of questions come to mind & wonder if someone here might give me an idea of best practices.

    If the OSB is removed, I'm reading that something should be installed in its place? I assume just laying the hardwood over the sheeting isn't advised, but what is the reason for this add'l layer?

    Also wondering how best to remove the OSB where is runs up to kitchen cabinet w/ toe-kicks? At the walls, we'll probably find the OSB butts up to the wall. But I would assume the original builder put down the OSB & installed the kitchen cabinets over the top. How does one get a nice clean cut line in the toe-kick areas and even up against the cabinet units?

    Altho' hubby & I have done some home improvements, flooring has not been one of them. Fortunately for us, hubby's boss was a very good contractor in his former life and he's willing to give us some assistance if we need it.

    I appreciate your comments & thank you.

  • 17 years ago

    It sounds like that may be particle board underlayment instead of OSB. Typically underneath the PB will be a 1/2" CDX plywood subfloor and you will need to go back and add a plywood underlayment over it, 1/2" minimum, but I usually use a 5/8 BC grade square edge plywood for that. A Crain Toekick saw is used to cut within a 1/4" underneath cabinet toe kicks.

  • 17 years ago

    Thanks Jerry....When we take up the carpet, if it is OSB, will we see it stamped on the boards? Otherwise, how do I know if it's PB or OSB?

  • 17 years ago

    OSB is big flakes and strands, of wood going all different directions.

    Particle board, looks like saw dust glued together, thus particle in the name.

  • 17 years ago

    It looks like we have OSB; it's definitely made up of larger flakes/strands. I'm still wondering it removing the OSB & replacing it w/ the hardwood only is going to give us future problems. The nice thing is that removing the OSB & replacing it w/ the 3/4" means the doors will all still open/close w/o any adjustment. If we add another layer (meaning sheeting, OSB, & hardwood), will the build-up be high enough to require other adjustment such as modifying thresholds into other living spaces, doors, etc.

    As you may see from my questions, it's a new experience for me and my hope is that we won't encounter too many surprises from failure to ask beforehand.

    Thanks again.

  • 17 years ago

    It's good to ask... so I suggest you verify a few things. Do you know for certain that you have a double layered substrate? If you do have two layers you need to determine what the bottom layer (subfloor) is and the thickness of it.

    If you only have a single layer and the OSB is 3/4" thick and T&G, that is acceptable to leave in place if its in good shape.

    Better give us your floor joist on-center measurements too while you are at it.

    last question... will you be installing the wood perpendicular or parallel to the floor joist?

  • 17 years ago

    Thank you Jerry_T for responding. I'll check that out & get back to the board asap. Hope you'll be reading over the next day or so.

  • 17 years ago

    I'll be around but please keep in mind that there are several top notch installers who contribute here regularly and may not see your questions. You could start a new thread if you like.

    Have a great Easter!

  • 17 years ago

    Jerry_T: We finally started on our flooring. Took up the carpet & pad and found it wasn't OSB but rather pressboard underneath. Below that is plywood sheeting running across the joists.

    We plan to pull the PB and replace with plywood (3/8" enough in your opinion running opposite the main sheeting??) before putting down the moisture barrier and the hardwood. Think we'll be much happier in the long run. A little more work, but this is a lifetime house for us (living on the family farm) and it will be worth it, I'm sure. I so appreciate people like you willing to share your opinions/experiences. Reinventing the wheel isn't something most of us wish to do. Thanks again.

  • 17 years ago

    You are correct in removing the Particle board. I still don't know what the subfloor is but typically a 1/2" CDX "square edge" plywood "sheathing" grade plywood is used there. Sheathing grades have voids in the inner plies and no T&G joinery.

    I like to use 5/8" BC (underlayment) grade square edge plywood or at the very minimum a 1/2" BC. The 3/8" will work but going thicker is much better here because nothing is T&G.

    Run the new the plywood underlayment crossing the joist, which usually means in the same direction as the subfloor. Keep all the sheets offset and staggered so no joints line up with the subfloor underneath and maintain a 1/8" gap alway around each sheet.

  • 17 years ago

    Still need to know which direction you intend to run the hardwood flooring, that fact too needs to be known as far as the underlayment thickness goes.

  • 17 years ago

    jerry_t:I appreciate you're still hanging in here w/ my questions.

    I believe we have 3/4" plywood underlayment running across the joist; nothing T&G here. We think we'd like the hardwood flooring to run across the joists. Our family & living rooms have a small area where they almost overlap and if the flooring runs across the joists, as you enter these rooms from the outside, the long hardwood seams will run left to right rather than straight ahead of you. Thought that might be more appealing visually. Also means that an approx one foot width of flooring will run thru the familyroom into the living room & down a short hall. That length is about 35' in length. If we chose to run the flooring with the joists, the longest run of flooring might be about 20'. I'm not sure that this really matters, but if it does, then perhaps other thoughts on the direction might change our minds.

    Thanks again & I appreciate knowing it's 'sheathing' rather than 'sheeting'. I'm learning. :-)

  • 17 years ago

    Thats Ok, I only pointed out "sheathing" because it is important for people to know the difference between a sheathing grade plywood and an underlayment grade. Sheathing grades only come in a square edge (no t&G) but underlayment grades can come both ways, thats where it all gets confusing again.

    Foe example , your subfloor is 3/4" thick, that is OK for installing hardwood. It is made of plywood, that's also good. But, there is no t&G, that is bad and you can be fairly certain that it is a sheathing grade, which means it is not intended to have a finished floor applied directly on top. Sheathing grades have voids (hollow spots) all within the inner plies. Not good for holding thousands of flooring cleats/staples.

    I suggest adding a "minimum" layer of 3/8" BC underlayment grade (no voids) plywood there after you remove the particle board. That gives you something for the fasteners to hold to and also will take care of the problem of having no T&G which results in sagging between joists.

    If your subfloor turns out to be a 1/2 or 5/8 thick instead of 3/4", then I would go with a 1/2" BC underlayment.

  • 17 years ago

    Thanks jerry_t - this has been a great learning opportunity for me. Think that w/ your help, we're on the right track. I've found these forums to be most helpful over the years & people like yourself help make that so. Thanks again...

  • 9 years ago
    last modified: 9 years ago

    Hope someone is still reading this....I am in the same situation as the original comment, except...now I'm hearing that they have to remove my 3/4" OSB ( why I don't know) to put plywood down (which will be expensive). ..How can they do that if the walls sit on it...also if they don't remove it it will add and inch and a half to my floor height, that will cause issues with my doors to rooms and exit doors...will it not? I have had two companies say it can go on the OSB and the one that has what I want says no. I'm wanting Acacia 2 1/8" x 3/4" installed. Desperate for the truth!

  • 9 years ago

    Start a new post, that's the best way to get peoples current attention

  • 9 years ago

    All depends on the OSB. Removing it might open a can of worms...and you can just imagine how hard could be to get those worms back in that can!

  • 9 years ago

    twofor,

    I am going through the same problem as well.

    https://www.houzz.com/discussions/yanchi-1-2-thick-strand-woven-bamboo-flooring-dsvw-vd~2975955

    Here's a conversation that I started... some people suggested that I take the OSB off the top and add Plywood.

    After some consideration. I don't really care anymore and I think it should be fine. 15 ga and 16 ga is very little difference in diameter of size of nails. As long as your subfloor is Plywood I would believe it would be fine. I am going to screw down the OSB that sits ontop of the Plywood. The nails that I am driving will be long enough to go through the OSB and into the Plywood on the bottom.

    My flooring is... 3/4" Plywood Subfloor with 5/8" OSB ontop. I'm not about to go through and redo 1000 sqft of OSB flooring ontop. I'll let you know in 10 years how the floors hold up... hahaha

    http://www.hoskinghardwood.com/Department/Hardwood-Floors/All-About-Subfloors--installing-flooring-over-various-sub-floors.aspx?dId=7&pageId=2




  • 9 years ago

    If you must go over OSB, use divergent staples, not nails and not cleats.
    Make sure the length, does not break through the OSB, or you will lose holding power and a squeak may be heard, as the fastener slides up and down in the OSB.


  • 8 years ago

    If your subfloor is at least 23/32" and you use one of those hardwood nailers that drive the cleats at an angle into the edge grooves, thus locking the cleats in place. I don't see how they can possibly pull loose.

  • 8 years ago
    last modified: 8 years ago

    "I'll let you know in 10 years how the floors hold up... hahaha"


    6 months into 10 yrs??

    Its common knowledge in the pro wood floor industry that OSB is not smartest for wood installs and to me is a cut corner that may bite you in time.

  • 8 years ago
    last modified: 8 years ago

    "Its common knowledge in the pro wood floor industry that OSB is not rated for wood installs and is a cut corner that will bite you in time."

    Thats not true....NWFA does allow for woodfloors to be installed over OSB.

    "The National Wood Flooring Association and the
    National Oak Flooring Manufacturers’ Association
    have issued official policies on the use of hardwood
    flooring over OSB. Both associations recognize 23⁄32”
    or thicker OSB panels certified to U.S. D.O.C.
    Voluntary Product Standard PS2 as an acceptable
    underlay for nail-down wood strip flooring under
    prescribed conditions"

  • 8 years ago
    last modified: 8 years ago

    just incase tellyouwhat wanted to do some reading to learn the truth and quit spreading lies

    http://www.hardwoodfloorsmag.com/installation/preparing-a-subfloor-for-wood-flooring.html

  • 8 years ago
    last modified: 8 years ago

    wow gregmills tell u what relax .sure a specified approved can be spec'd and is.

    still most every wood installer ive worked with will say otherwise in regards to wrrty there work specifically single layer standard sheathing osb panels and nail down

  • 8 years ago
    last modified: 8 years ago

    agreed and ill tell you what you are right on somethings, as explained above its the material type of osb was concerning

  • 8 years ago

    Telluwhat, if you read the recommendations from the NWFA carefully.. They do not have a problem with OSB subfloor as long as the thickness is a minimum of 23/32" and of product standard is PS2.

  • 8 years ago

    I've seen this conversation go back and forth on a lot of forums.

    Some say it's OK, some say it's not OK. For those who are attempting it to do it "Right" - Plywood is safer than OSB. OSB is not absolutely the worst thing out there, it will get the job done.

    You can say all you want about OSB, but I actually did it and live in it. I will let you know in 10 years if it holds up or not... and honestly I am pretty sure it will hold up. At first I was unsure, but I bought the OSB over the Plywood and I installed everything myself. I wasn't about to pull out all the OSB to place Plywood on top. I did a short cut. If you are someone that comes across this post, and unsure about Subfloors go buy Plywood so it will put your mind at rest.

  • 8 years ago
    In regards to using OSB, I have the following comment: I am a structural engineer in California, and I have specified OSB as a subfloor, roof sheathing & shear wall sheathing for hundreds of homes. As far as an underlayment for hardwood floors, there appears to be two issues. 1) is the floor structurally sound for hardwood, and 2) whether attaching the hardwood directly to OSB will result in nail slippage many years down the road. I have comments on both issues. As far as the floor being structurally sound, I have seen a few posts on this issue & I am not one to automatically say that hardwood should be placed perpendicular to the floor joists... But it would definitely be stronger and may help in easily repairing the hardwood attachment if the nails should slip many years down the road. I myself have placed the hardwood parallel to the floor joist because my subfloor is very stiff. To get a stiff floor, this is my recommendations: joist spacing should not exceed 16"o.c.; floor joist span should be designed conservatively (building code minimum is not conservative), and floor sheathing should be 3/4" nominal and placed with the face grain (long dimension) perpendicular to the joist & staggered. In regards to item 2: some national floor associations have said direct OSB attachment is acceptable as long as sheathing is PS2 standard & 23/32" minimum. That is all we can go by. As I mentioned above, let's say the nails do slip after many years... If your hardwood is perpendicular to the joist, couldn't you just screw it down to the joist below as a repair? That is one benefit I can see with placing the hardwood perpendicular to the joist or adding blocking between the joist.

    In regards to nail slip, I posted a blog regarding using the hardwood nailers that drive the cleats at an angle in the tongue of the hardwood edge. The cleats are locked in place inside the T & G connection. How is this going to lift up? Also when you drive the nail at an angle, there is a vertical bearing component of the nail that is preventing the nails from lifting. This is versus using a brad nailer that goes vertical. The vertical nail would rely totally on friction between the OSB & nail and I can see this possibly slipping down the road.
  • 8 years ago

    Sorry let me edit my comment... My SUBFLOOR is Plywood. I added another layer of OSB ontop of my Subfloor. Ontop of that I placed 3 mm underlayment and then I nailed the Bamboo over that. The 2" T-Cleat is long enough to pierce through Bamboo, OSB and Plywood. I did my kitchen with Plywood Subfloor, Underlayment, Hardie backer board, then Tile. The Tile and Flooring transition is perfect so I didn't use flooring transitions from Bamboo to Tile because it looks ugly.


    As I was ripping out the kitchen floors, the previous contractor used OSB as the subfloor for part of the Kitchen and I was able to rip that out with my bare hands due to the water damage done to it. OSB loses a lot of its structural integrity when it is in contact with water... Any areas that are prone to possible water leaks I would suggest using Plywood over OSB.

    hope that helps.

  • 8 years ago

    I keep hearing sub flooring under the OSB. We have OSB looking at me when I tore up the carpet and padding. When I look at my floor from the basement it is deffinetly OSB. The OSB is the Only floor under the carpet. It is 23/32 thick is says PS 2 too. So do I need to take up the OSB and put plywood down or SHOULD I add plywood onto the OSB, or can I put hardwood over what I have. Help

  • 8 years ago
    I have 15/32" PS2 OSB sheathing and I recently added 3/4" thick solid hardwood and so far, after 6 months, I have had no problem. I am a structural engineer and I made sure that the floor framing "I" joist where I added the hardwood was designed very stiff....therefore I did not hesitate to place the hardwood parallel to the joist. I think if your floor is not stiff & flat, that could be the #1 reason that nails could pull out. I also read somewhere in this blog that says cleats are no good. My opinion tend to differ because the cleats are installed along the tongue of the hardwood and driven at an angle. When you drive the cleats at an angle into the OSB, there is a vertical component of bearing of the cleats that is preventing the nails from lifting up. When you nail down the hardwood vertically, as you would a brad nailer, you are relying totally on friction. From a structural standpoint, bearing is always better than friction
  • 8 years ago
    Oops... I n my previous post I said I have 15/32" OSB. I meant to say 23/32" PS-2 OSB. I would not recommend installing nailing hardwood to anything less.
  • 8 years ago
    last modified: 8 years ago

    I would also suggest using glue along the edges and the first couple of rows and the last few rows against the walls. I didn't and I notice it a little bit, but I don't really care that much since I did all the work myself.

  • 6 years ago

    Would any of you flooring contractors feel confident about installing a wood floor over 5/8" p2 osb with a layer of 3/8 " plywood on top?

  • last year
    last modified: last year

    7 years later my floors are fine. hahaha


    be sure to eliminate any squeaky areas / loose areas of the floor prior to putting down the OSB and Hardwood. sub floor should be solidly stuck to the joists or you're going to get squeaks.


    Happy DIYing