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Community and Q&A

Vapor barrier for floating cork floor

ravens_42 | Posted in GBA Pro Help on

I live in Peoria, Illinois (Zone 5A). I’m installing a floating cork floor over an upstairs plywood subfloor. Nearly every website I see preaches on the importance of using a vapor barrier under floating floors, but I’ve also seen vehement advice against it. The planks I’m installing have a thin cork layer on the bottom, so I really shouldn’t use a vapor barrier right?

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  1. Expert Member
    Dana Dorsett | | #1

    If it's heated conditioned space in the room below (or even an unheated basement) there is no call for installing any sort of vapor barrier there.

    On an open pier foundation with an insulated floor and OSB sheathing on the underside it might be a good idea, but even then it's not an absolute.

    What IS the space below the floor?

  2. ravens_42 | | #2

    The space below the floor is my garage and basement, which often get pretty moist during the humid days of summer. The subfloor sits directly over joists with fiberglass batting between them in some areas, but there are also parts without batting.

  3. ravens_42 | | #3

    BTW, the basement is heated and air-conditioned, but the garage just gets warmed by a small space heater during the winter and nothing else.

  4. GBA Editor
    Martin Holladay | | #4

    First of all, flooring should always be installed according to the flooring manufacturer's directions. If you don't have a paper copy of the installation instructions, you can usually find them online.

    Second, I strongly advise you to insulate your floor assembly properly before installing finish flooring above the floor assembly. For more information on insulating this type of floor assembly, see How to Insulate a Cold Floor.

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