Final debate on LVP over concrete
So I asked this question numerous times and maybe I’m beating a dead horse but I seem to still have conflicting answers. Life proof lvp directly on old slab with no moisture barrier. Some have said yes I have done this and seems to be holding up. Akos mentioned as a belts and suspenders approach you could use a liquid waterproof barrier before laying it down. Some have said basically I am asking for mold. I have seen the guy on renovision say not to do it while another expert on basements said you could put like deltafl or something underneath and would never be a problem. So what is the actual answer, and I know it may depend but is vinyl plank a vapor barrier or not. Is it waterproof? If not what is in it that grows mold? Also if mold could grow underneath the flooring would it actually ever reach the air. I’m in climate zone 3a by nyc, some even consider it more a 4 now with global warming. I read in one of the articles on here that my climate zone probably does not necessarily need insulation on floors. I only care about mold and ceiling height nothing else. I might also add I had to rip up a small section of old stick on vinyl off basement floor years ago and I didn’t find any mold it was just a pain in the *** to rip it up. If I need anything underneath as just a extra precaution what would it be? Also what about PT plates on floor in basement, aren’t they for exterior, do those grow mold too?? Do you need something underneath them? I have even read not to put foam board against foundation because it traps mold and moisture. Why is there so many conflicting thoughts??
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How about trying the old trick of putting down a sheet of plastic over the slab, edges taped, and see if there is moisture coming through getting the bottom side of the plastic wet?
Joe, you will rarely if ever find full consensus on GBA's Q+A section. You have received a lot of solid information--enough for you to make an informed decision one way or the other. Some approaches are tried, true and safe; others are definitely risky, and yet others are somewhere in between--somewhat risky, but maybe or likely fine.
Why so many conflicting answers? Because every house is a unique system of variables, the science is relatively complex, and everyone comes in with different experiences and priorities.
My experience is mostly with older homes in a cold climate, and I have researched mold enough to be very wary of it. I design projects for clients so I can't take risks. Others work in warmer climates where things like a 10° warmer ground temperature can make the difference between high risk of mold and low risk of mold. Others may not feel that mold is as large a health concern as I do.
When you have a lot of questions, or interconnected questions, it stretches the limits of what a web forum can provide. Many of us make our living advising people on what to do in cases like yours. If you feel that you aren't getting clear enough advice here, I recommend finding a local expert in waterproofing and finishing basements to advise you or to do the work.
As for plates, any wood in direct contact with concrete or masonry that could be damp or cold should be rot-resistant, typically pressure treated but naturally rot resistant is ok too. The same compounds that make wood rot-resistant, naturally or artificially, also make it mold-resistant.
What does the LVT manurfacture recommend?
Charlie, I will try that test. Should have done that a while back.
Jonathan in terms of lifeproof the warranty is voided if you put an underlayment unless you use their specially designed one. So basically they don't want you putting anything.
https://www.mpglobalproducts.com/blog/does-lifeproof-flooring-require-underlayment/
Michael I have spoke to local experts on waterproofing and finishing basements. The answers I have gotten have varied. That is why I come here because this is all about building science. I would like to be informed before making a decision. Half of my questions on here is me checking if the person I'm about to hire really knows what they are doing or if they are full of it. I have no problem hiring an expert, they def deserve to be paid for their expertise but if I feel like their work would make my house worse then I want to avoid it. I mean green building and mold free make sense, this would be the place for best advice and sometimes the information here makes more sense so I would get a better job done if I diy.
Joe, in that link you provide, they do recommend a poly VB. No?
I didn't see the other exchanges on this matter, but if you're concerned about moisture migration up from a slab, it seems like taking steps to prevent that migration would be the conservative call. But I can't speak to the specifics of that product whatsoever.
Beside doing the taped down plastic test, one option is to lay down say two boxes of flooring in a smaller room as you intend and check on it in about a years time. If it looks good, it would be pretty safe to do the whole basement that way.
I have two century homes with LVT over the bare concrete without a VB underneath. No issues with either place, both had dry basements to start with.
Have you considered that LVT is not the best solution for a floor. It is going to be cold underfoot without insulation from the slab. If it is cold, no one is going to use it. Also, is that floor dead flat? I think I would paint the floor and put down some indoor/outdoor carpets.
Copying from an earlier post:
>>>>Begin quoted text
There are four ways that moisture gets into basements:
* As groundwater that comes up from below. This is avoided by having perimeter drains and possibly a sump pump.
* As rainwater that runs down the walls. This is avoided by having a waterproof rain screen that allows the water to flow down to the bottom of the wall, where it is collected and diverted by perimeter drains.
* Through capillary action as moisture wicks through the masonry. This can be avoided with a barrier.
* Through condensation, when warm humid air contacts a cool surface. In Virginia, this is going to be a huge issue. To fight it, you have to seal the walls to keep outside air out in the summer, and also seal the walls to keep interior air from contacting the cool parts of the wall. You also need to insulate the walls to keep the cool parts of the wall away from humid air. Removing humidity from the inside air -- using either AC or a dehumidifier -- also helps.
>>>> end quoted text
Your basement needs multiple layers of protection: a rain layer, a vapor layer, an air layer and an insulation layer. All of those layers have to be made of impermeable materials.
So:
* Is LVP waterproof, in that it would keep out liquid water? No.
* Is LVP impermeable? Yes
* Does LVP form a vapor barrier? Arguable, I'd say yes.
* Does LVP form an air barrier? Again arguable, I'd say yes.
* Does LVP provide insulation? Some. Is it enough to keep the surface above the dew point? Maybe. It depends entirely on your local conditions.
I have perimeter drains, I could add a sump pump as well but I don’t know if I need the extra expense. I’m thinking level the floor to a flat surface, seal it with a moisture barrier, put 6mil vapor barrier, add dmx one step or deltafl, and finally the lifeproof lvp. I like carpet like Jonathan mentioned so I could add as a final layer synthetic area rugs. Lifeproof also makes a waterproof carpet pad that they claim can go over concrete. Not sure if this would work with a synthetic rug, any opinions?
7/16 in. Thick Waterproof Premium Plus Carpet Cushion with Air Channels and Ultra-Fresh
https://www.homedepot.com/p/312019782
I’m thinking moisture would have to get past moisture seal, then pass the 6mil poly, if liquid water would even get to the top of poly it would be in an air gap and not soaked up by bottom of vinyl flooring. It would have to evaporate into the air which a humidifier could control. I’m not a building scientist by trade this is just what I think in my head, could be totally off. Also all these layers would add some insulation to prevent condensation.
I used a dritac product to hold down plywood on a 1970 floor
this appears to be their product for what you want:
https://www.dritac.com/product/dritac-5900-megabond/
I have no experience other than 11 years without problems with another product of theirs