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Hardwood floor underlayment

Thomas Tzeng
December 3, 2018
last modified: December 3, 2018

I am researching hardwood floor underlayment for pre-finished Mirage hardwood floor. A constraint is that I already have wood tile floor in the bathrooms and would like to make the tile and hardwood floor flush. I measure the tile floor it's about 3/4" and my hardwood is also 3/4". Dose this mean that I can only use paper-thin underlayment, and can't use some things like QuietWalk which is 5mm? We'll use nail down installation for hardwood floor.

Comments (13)

  • PRO
    G & S Floor Service

    Use Quiet walk plus, it is designed for nail down installation. Whereas Quiet Walk is for floating floor installations. You will have a small height difference, around 1/16".

    Thomas Tzeng thanked G & S Floor Service
  • PRO
    Johnson Flooring Co Inc

    What is the purpose of the underlayment?

    Thomas Tzeng thanked Johnson Flooring Co Inc
  • SJ McCarthy

    AS G&S suggests, use Quiet Walk 3mm. It is a nice product for residential installation. A T-moulding or uneven T-moulding can deal with the transition at the doorway. This is absolutely normal.

    Thomas Tzeng thanked SJ McCarthy
  • Thomas Tzeng

    It looks like Aquabar and HWD-15 are vapor barrier, and QuietWalk plus has additional features. Would this make QuietWalk plus a preferred option? I have plank subfloor over crawl space. It looks like I may need to use T-molding at the transition if I use QuietWalk. I am not sure if we can sand/cut 1/16" the back of the hardwood at the transition to make it flush with the tile without using T-molding?

  • PRO
    G & S Floor Service

    If, you want to keep the cost low. Use Aquabar, it has a .8 perm rating and is preferred over crawl space.. If, cost is not an issue and you would like the added warmth, sound control and a quality vapor barrier, use Quiet Walk plus. I would glue down the quiet walk plus versus tacking it in with staples. The glue will add to the performance of the product and keep it nice and flat. The staples will be loose and the joints can get all mushed up, causing added work with installation, flattening the underlayment.

    Thomas Tzeng thanked G & S Floor Service
  • PRO
    Johnson Flooring Co Inc

    I see no reason to use anything more than Aquabar, which doesn't add to your wood floor thickness.

    Thomas Tzeng thanked Johnson Flooring Co Inc
  • Thomas Tzeng

    I can't find technical data about QuietWalk plus regarding perm rating. Does it comparable to Aquabar? QuietWalk also demonstrates the ability to avoid spill water damage the floor and subfloor. Is Aquabar also cable of doing this?

  • Thomas Tzeng

    If we were to glue down the quietwalk, I wonder if it brings a concern about VOC of the glue.

  • PRO
    Johnson Flooring Co Inc

    Not sure what you're asking about spill damage.

    Thomas Tzeng thanked Johnson Flooring Co Inc
  • SJ McCarthy

    You're on a planked subfloor and about to nail down your hardwood. Which ever underlayment you use, you will puncture it with THOUSANDS of nails. The perm-rating won't matter because of all the holes you just punched into it.


    We need to know the PURPOSE of your want for underlayment before we can comment on which one works for your situation.


    And any spills that make it through to your SUBFLOOR or your CRAWLSPACE will be SOOOOOOO large that your flooring will suffer the most. You aren't protecting the subfloor with the underlayment. You are protecting the floor from the crawlspace.

    Thomas Tzeng thanked SJ McCarthy
  • PRO
    G & S Floor Service

    Quiet walk's vapor barrier is designed to seal around the nails or staples, when shot through. The heat melts it in place. The built in vapor barrier disperses the vapor to the perimeters. The 1/2" gap left at the perimeters allow the moisture vapor to escape. I believe the perm rating on it is .7 , which is below recommended rating. But the product is approved for wood floor use. NWFA had a course on their products. You cannot use quiet walk on subfloor that measures above 7lbs of vapor pressure. It needs to be dry.

    Aquabar allows vapor to go through the material at a slow rate, but deflects most of it to the sides and up the walls.

    If, your crawl space is less than 18" high. You need to get it weather wrapped before starting the installation.

    Thomas Tzeng thanked G & S Floor Service
  • Thomas Tzeng

    Because I purchased Mirage solid wood and it suggests use of #15 felt paper, I think Aquabar is my default choice. The features offer by QuietWalk+ are nice to have. If the crawl space is more than 18" high but the relative humidity in the crawl space might be high in rainy days, QuietWalk+ may not be a good choice in such case? I live in CA bay area which is normally dry but not too dry. BTW, should both Aquabar and QuietWalk considered as vapor retardant, not barrier?

  • PRO
    G & S Floor Service

    I apologize for the confusion. I have a tendency of calling these products barriers. You are correct these are vapor retardants, not barriers.

    Thomas Tzeng thanked G & S Floor Service

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