Subfloor-pressure treated plywood?

I bought some PT for my subfloor and it will be used in the living room area. My foundation is on beam and will be insulated. I did not know different types of subfloor or wood type shoud be used. But thought it was a good idea to use the PT wood since it has been treated. This wood has no tougue or groove some contractors have said that it was not a good idea to use without tongue and groove, because the edges will lift later. It was an expensive buy, bought it for few months now but have not installed them permanently to the floor. Is it a good idea to use it or just replace it with a regular OSB with tongue and groove. Please help! I would hate to waist this PT wood. What is the true pro and con harm by using it??Thanks,

ldduong

in Brownstoner Renovation 10 years and 6 months ago

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dorkofwindsor | 10 years and 6 months ago

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FYI – CCA has been banned for residential use – so the old stuff is still dangerous for kids to come in contact with, but the new stuff is fine. One option, if you want the best of both worlds, is to whip out the router and make your own T&G.

brucef | 10 years and 6 months ago

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Setting the question of pressure treated aside, oneone of your questions regards T&G versus square cut. It is true that T&G will add strength to a structure that needs it. Hopefully a brownstone joists are strong, and are not in desperate need of reinforcements. Square cut does have some advantages. For instance T&G measures 48″ overall, but you need to subtract 1\2″ overlap. Not a big deal unless you have joists 12″ on center. Similarly if you start at one side and go all the way in one shot, having a ripped piece the right size, but with the tongue on the wrong edge causes more waste. Gluing and screwing is very strong when done right. Good square cut plywood I would take over what usually comes as sub-floor T&G 9 out of 10 times. Not using new formula pressure treated sub floor is like political correctness. Given precaution while cutting, this product will be encapsulated in its installation. If one sought a reason not to use it, could you find someone with a qualm? For sure. Is it a glaring danger? Hardly. Those of us old enough survived cars without seatbelts. Smoking cigarettes, drinking alcohol – now these are some truly proven dangerous habits. But I think hysteria over new fears is a lot easier than tackling proven, widespread harmful habits. Just sayin’

resident2 | 10 years and 6 months ago

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Pressure treated plywood is Not meant for interior sub-flooring. Even besides all the above noted toxin issues, it will warp and expand and contract at a rate that you will not be able to keep a prime floor stable, it will all look a mess within a year or two.

nyc_sport | 10 years and 6 months ago

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I have no views on the off-gassing question, but I would be far more concerned about other aspects of pressure treated woods. Pressure treated wood by design retains moisture, which could seriously affect any hardwood laid on top of it (or any sort of tile). It also may be difficult to glue, both in terms of gluing it to the joists and gluing any floor if you are laying wide hardwood. You also need to consider the method of fastening, as it typically corrodes ordinary fasteners. And, perhaps because of the moisture content, it tends to bow and check more than ordinary wood.

thetinkerswagon | 10 years and 6 months ago

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I would check this product out further and see what that wood is treated with. I just took a brief look at the use of CCA in lumber products and it turns out the ban was not a mandatory ban but the EPA asked companies manufacturing deck material and play ground equipment to voluntarily stop using it. I would also read about the health effects as maybe they are blown out but I would still be careful where children are concerned just because their bodies absorb toxins at a greater rate and they have so much time in front of them for these things to turn into something else. I don’t usually like to weigh in here with things where I do not know what I am talking about and I am not really in the know about this stuff as I never bothered to learn because I am not a deck builder. I am raising a flag because so many other people, including contractors and others who work with the stuff, have made such a big deal out of it and I have been hearing this since the 1970’s when creosote drifted into history. Better safe than sorry, esp with children. Steve

daveinbedstuy | 10 years and 6 months ago

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Glue it down on the joists and it will be even stronger. No more toxic gasing problems

thetinkerswagon | 10 years and 6 months ago

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and in spite of my warning about that product, when I built my shed out back, I used pressure treated plywood on the floor. Steve

thetinkerswagon | 10 years and 6 months ago

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I am chiming in here to ad on to what matt says. now, for years pt used CCA (I think that is copper chromium arsinate). with a name like that, it cannot be good for you. years ago, when I was a teenager, my grandfather was adamant that I not handle that stuff nor burn it nor do a lot of other things with it, including cut it; and let me put this in perspective, he had been an overhead lineman with the lighting company – so he was not someone to be afraid of things that may have gotten hands a little dirty or given someone a splinter and he was not into molly coddling his only grandson. this stuff is (or was) bad, bad, bad and you do not want your children around it. that said. my understanding was that the industry had been ordered by the Feds to stop using the toxic stuff in PT. I am not sure to what extent this ruling went, when it went into effect or if I even heard what I heard correctly (I caught something on the radio about it and did not hear the entire story). if it is true that they are not using CCA anymore, there is still the outside chance that you have some wood left over from the bad old days. I would not chance it. also, in the event that you did use and in a year from now had to sell your house and someone put children over that stuff, they may not be good. please read more about this product. Steve

mruby36 | 10 years and 6 months ago

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PT wood of any variety is wood thats been infused with chemicals that are highly toxic. I really dont know what or how much it off gasses or what it would contribute to the “interior pollution” of the space above it, but it cant possibly be worth the risk. Altering the assembly in reaction to the problem seems to me to be the wrong way around. The best assembly (what wood, insulation, sub floor, underlayment and finish floor) should be as chemical free as possible or practical. If you think you need PT, it must be because you think there is a moisture problem. The best solution is to solve the moisture problem. Period. If the ground under the floor it wet or worse, find the source BEFORE you craft a solution. Sometimes a simple rough concrete slab over the dirt will suffice. Try venting or create a cross-draft so moisture can migrate out, like gortex for your crawlspace. Or a dehumidifier. Investigate and solve the moisture problem and the rest is simple. Feel free to contact me if you wish. Best of luck! Matt R http://www.nyc-hs.com