Waterproof underlayment for LVP over concrete basement floor

7 years ago

I’m installing 5mm LVP (w/o padding) over the concrete floor in the basement. The floor is generally dry, but I’d like to have some vapor barrier protection and the cushion. I’m concerned that a vapor barrier would trap moisture underneath it. I’m avoiding a simple plastic ones for that reason and looking into underlayments that are designed for LVP (such as FloorMuffler LVT). Would that be sufficient or do I still need to be concerned and look into membranes (Platon, Superseal) that allow airflow?

Featured Answer

SJ McCarthy

7 years ago

I'm sorry but the manufacturer dictates what can be used with vinyl. Vinyl HATES underpadding. You cannot use anything other than what the manufacturer recommends.

Even with the underlayment, you will need to work with 6mil plastic sheeting. I'm sorry but this is the best way to work with flooring in a basement. The vapour barrier (6mil poly sheeting) is the industry standard. The Tranquility LVT Underlayment is what I would work with on top of the plastic sheeting. You need an underpad that is SPECIFICALLY designed for LVP/LVT. Tranquility offers you the precise product recommended for your Lumber Liquidators vinyl. There is no reason to change it.

Please don't try to reinvent the wheel. These companies have done hundreds of thousands of dollars and thousands of hours of testing to figure out the BEST way to get their products to work.

If you feel the need for 'more' protection without the possibility of mold/mildew, you are welcome to have a basement water proofing company come in and do a basic shot blast/seal/prime/microtop your entire basement before you install the LVP. This service can run $5/sf or more...depending on your location or the issues they find once on site.

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Comments (7)

millworkman
7 years ago
What does the manufacturer of the flooring recommend for this application? At the end of the day, they warranty the product, and if you want said warranty you need to use their recommended product.
Konstantin
Original Author
7 years ago
They have their own underlayment similar to FloorMuffler. But, they focus on protecting the floor, I'm trying to eliminate potential moisture, mold, etc. issues.
The floor I'm installing is https://www.lumberliquidators.com/ll/c/Riverwalk-Oak-LVP-Tranquility-Ultra-5RWO/10041017
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Konstantin
Original Author
7 years ago
Thank you SJ McCarthy. I do understand I have to (and I will) use an underlayment designed for LVP. From my research FloorMuffler LVT is one of the best products for that on the market. Hence I prefer it over the one by Tranquility (that doesn't even have a way to contact them other than through Lumber Liquidators that actually tried selling a different underlayment).

Again, my main concern is what's gonna happen under the vapor barrier all these products provide. I hear you about industry standard and I do question it. There are a few products on the market (Superseal, Platon, Dri Core). These are called subfloors and they all push for having airflow to make sure moisture is not being trapped under the poly sheeting. Is that a different standard? Perhaps, I'm missing something, but it feels like the right thing to do albeit for extra cost.
SJ McCarthy
7 years ago
If you are concerned about the possibility of mold/mildew, then the most effective thing to do is fix the concrete so that it doesn't have a problem. You could spend $2-$4/sf on materials (such as DriCore) only to have a damp slab underneath. Which means the potential for mold is STILL THERE.

Or you can fix the problem at its source: seal the entire slab properly. That means shot blasting, etc. Which isn't much more money per square foot than the $4/sf for the EXPENSIVE DriCore. And if you read DriCore's website, they will require a 6mil vapour barrier UNDERNEATH their panels if the hydrostatic pressure is higher than 'x' lbs/1000sf. That's for the 'regular' DriCore. To get away from this requirement you have to use the HIGH PRICED foam panels. And then you have to purchase OSB/Plywood to go over top of the foam panels....etc.

Industry Standard means just that. The industry (flooring) recognises that slabs almost always contain moisture. The control of that moisture is up to the homeowner...but the flooring professional can take steps to ensure the product THEY are installing will have the best chance of being successful in that space. That means stopping moisture from 'hitting' or reaching the floor above. What happens underneath the vapour barrier is up to the homeowner to deal with...because the homeowner is ultimately responsible for his/her cement slab. The professional has done his/her job by using the industry's regularly used product such as 6mil poly sheeting.

Again, if mold/mildew are your concern (and it should be) then the 'fix' is not going to be some panels sitting 1/2" higher than the concrete. The fix is going to be the professional sealing of the slab. Shot blasting is a b!tch! The epoxy sealants are a b!tch to work with. The primer is noxious and the microtopping is a nightmare. Which is why it is best to leave the sealing of slabs to the professionals.
Konstantin thanked SJ McCarthy
Konstantin
Original Author
7 years ago
I appreciate the feedback! It makes sense. I wouldn't go for DriCore - too expensive. The Superseal I mentioned is less than $1 per sq. ft., but it sounds like there's not much value in installing subfloor. I guess I'll just go with FloorMuffler LVT that has the vapor barrier and good IIC/STC ratings. Thanks!
HU-18988608
4 years ago
What is LVT?