Underlayment for Glue Down LVP

6 years ago

last modified: 6 years ago

I am installing Karndean looselay in a new addition soon. The distributor came out and looked at my setup and decided that it would be best to do a full tack adhesive since I will be using it in a bathroom and large areas.

We currently have Advantech wooden subfloors. I am super confused about what underlayment I should use and the proper way to install it. The Karndean instructions are vague at best.

Do I use plywood underlayment or can I use foam?

I would think I would need to glue down the underlayment since the flooring will be glued. But many of the foam underlayment instructions say that you don't need to do double glue except in commercial settings. They recommend floating the underlayment, and then gluing the floor to it. Like this one.

Help! Need someone to point me in the right direction.

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SJ McCarthy

6 years ago

Yes....several people have tried it. They are the one's complaining about the mess they are in with their Karndean floors.

Advantech is normally good enough for most things. The *problem I see is the "smooth and level the joints/screw heads..." part. That's where EVERYONE gets into trouble. No matter WHAT type of wood underlayment you have, it has to have MORE than just the "patches" done (to cover the screw heads/joints).

You will NEED to have the whole thing SKIM COATED. I know. It doesn't "say" that in the installation instructions....but the words "smooth and flat" IMPLY that you must have a perfectly flat/smooth surface. Those people who have tried to patch (cement patch over screws/joints but not over the entire surface) have had problems. Lots and lots of problems.

Stick to your guns. Get the full skim coating that you need (regardless of plywood or Advantech) and go from there. The price is worth it. I promise.

It is better to pay a few thousand more today then it is to wait 12 - 18 months for Karndean to do anything about a 'bad' floor....only to find out it was a problem with the installation (subfloor preparation belongs to installation - not the floor manufacturer).

And just so you know, the Karndean Rep can tell you to install this on the MOON! It won't hold up in a warranty claim. Only Karndean Website "instructions" are valid. No statement, either spoken or written, by a representative will change the REQUIREMENTS written on the Karndean website. No matter how hard you try to argue (later on in court/mediation) you will never get them to stick to the word of their rep. Never.

If you worry about the Advantech, go ahead and lay down some 3/8" APA Underlayment grade plywood, have the ENTIRE THING skim coated and sanded smooth...and THEN start your Karndean installation.

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Comments (6)

SJ McCarthy
6 years ago
No FOAM! Underlayment, is a confusing word because it can refer to plywood, OSB, Luaun, concrete, etc. It also can refer to underpad (like the foam put under laminate).

I will say that 99% of all VINYL PLANKS do NOT allow under PAD (foamy squishy stuff). They MUST be laid over something hard. And if you glue DOWN then you are EXTREMELY limited.

Only KARNDEAN can tell you if the pad you have found is ALLOWED. The installation instructions will say: "Underpad specifically designed for Vinyl".

Those are the words you are LOOKING FOR! If you see them (IF....BIG IF) then the pad you have linked is ALLOWED. But you MUST SEE THE WORDS "specifically designed for vinyl" in the Karndean installation instructions. If it does NOT SAY IT...it is NOT ALLOWED.
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ladygibbs
Original Author
6 years ago
Thanks. The pads say they are for viynl plank but i didn't see foam listed on the karndean instructions. Thanks. I will stick with the apa plywood.
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SJ McCarthy
6 years ago
I've just read the Karndean installation instructions (for another thread) and there is NOTHING mentioning underpad specifically designed for vinyl. Everything mentioned is HARD AND FLAT!

Remember: make sure the installers coat the plywood in leveling compound to make it SMOOTH. Another thread has shown a wavy floor because the staples where left and the bumps and divots from the staples are telegraphing through. This is common with improper installation.

Please make sure your contract SPECIFICALLY STATES the subfloor preparation will be to "Karndean Specifications" and follows "Best Practices" for resilient flooring. These two statements will HOLD UP IN COURT! There is NO WIGGLE ROOM with those two statements.

And to be clear, that type of substrate preparation can add $2-$4/sf onto the cost of the installation. Just so you know.
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ladygibbs
Original Author
6 years ago
The Karndean distributor is telling me I can just smooth and level the joints/screw heads on the current Advantech floor and not add any underlayment... He says that is what he does and he is a professional/warrantied installer.

But the Advantech and Karndean instructions say to use an underlayment grade plywood ontop.

Has anyone prepped a new wooden subfloor and didn't add an extra layer of underlayment? It would be a lot less work, but I'm not sure I trust "the professional."
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ladygibbs
Original Author
6 years ago
last modified: 6 years ago
I have never heard of skim coating the entire thing. Definitely not common practice here...

Price is not the issue. I am doing the install myself, and I just want to do it right.

The last flooring I had laid was cheapo vinyl peel and stick tiles. A company came and laid APA plywood, didn't patch the joints and 5 years later that floor is still perfect.

I think I will go with my gut and use the underlayment anyway. It won't hurt anything, and I'd rather be safe than sorry.
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Underlayment for Glue Down LVP

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Underlayment for Glue Down LVP

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