My previous question, which led me to go with LVT, was answered here.

I saw this question and guess that (6-mil plastic) could be an answer but I'll give you guys the details and see what you think.

  • My bathroom subfloor is concrete and flat enough, looking to cover ~35sqft
  • I want as much thickness as reasonable up to 1/2" (12.7mm) to match the hall floor height
  • I bought Pergo DuraCraft WetProtect LVT (6mm thickness, click-lock, and attached pad) but am prepared to return it.
  • The seller recommended FloorComfort 2mm thick foam underlayment.
  • I just noticed the Pergo LVT says "Do not install over .. foam underlayment"...

Was I misled in getting the foam underlayment? Should I get a different underlayment?

Maybe should I go with SmartCore 9mm thick LVT instead to get more thickness? They have a 1.5mm underlayment approved with that LVT and would really take out some of the guesswork. I also see that SmartCore is made by COREtec and seems to be well recommended.

Thank you for your advice!

2 Answers 2


The floor comfort underlayment is to be used with laminate or engineered wood NOT LVT or LVP.

Go with the Smartcore and approved underlayment. I have used that brand and had great results. Better to use products matched to each other.

  • Thank you again, I’ll go with this! Glad I was particular about this and didn’t just blindly go along with what the guy at the store said. Might be saving myself from future headaches. When in doubt read the specs! :)
    – xtratic
    Mar 1 at 5:45

I'd use a 1/4" notched trowel with some stiff thinset mix. Trowel it on your floor surface leave the notches standing. Once stiff enough I'd fill the voids and flat trowel against the notches. This will bring your floor up the 1/4". A bathroom floor is so small and area it isn't that much work to bring it up 1/4".

Don't use another layer of underlayment, you can get too much deflection in the click lock system and break the tongues.

  • This is certainly a fair idea and could be the right answer for other people but likely not for me. I don’t think I want to raise the subfloor in such a permanent-ish way, especially since my vanity is already installed (planned to floor around it) and I would want to raise it all in one go.
    – xtratic
    Mar 1 at 5:36
  • I thought that’s what could be the issue with the underlayment. Thank you for confirming!
    – xtratic
    Mar 1 at 5:39
  • 1
    Even if your vanity is scribed to the current floor you can always raise the floor with thinset and when you go to do your LVP you'll probably under cut the vanity baseboard anyway? you typically want an expansion gap so you'll either undercut the vanity or you'll add another piece of baseboard to hide the expansion gap. thinset is always going to be a little bit softer than concrete so it isn't as permanent as you'd think... rotary hammer with a wide chisel and you'd chip it back off the concrete in no time. the toilet is the harder part. Mar 1 at 7:20

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