Suspended floor, laminate and vapour barrier

Discussion in 'Builders' Talk' started by adey49, Jul 13, 2018.

  1. adey49

    adey49 Member

    Hello, me and my mate were having a discussion about what type of underlay to use for laminate or engineered flooring when floated over floorboards.

    It seems all manufacturers now insist that an underlay containing a vapour barrier is used, even on suspended wooden sub floors.

    He seemed to think moisture would rise from the crawl space through the floorboards and get trapped under the underlay (as it has a vapour barrier) and over time rot the top of the floorboards.

    What he says makes sense and he was very insistent this could become a big problem as so many people have laid this type of underlay with laminate.

    But I was thinking what about all the houses where sheet vinyl is laid, surely this is itself a moisture barrier? The floorboards/plywood under vinyl are fine, so why shouldn't it be the same with laminate flooring? In addition what about rubber carpet underlay, surely this also acts somewhat like a moisture barrier?

    I think the issue is that neither me or me mate understand exactly what or how water vapour behaves!

    Any thoughts? Thanks,

  2. KIAB

    KIAB Well-Known Member

    IF you got good through airflow under suspended floor,air bricks front & rear of house clear of crud, then moisture shouldn't be a issue.

    Can also recommend Sonic Gold underlay, has built in dpm.
  3. adey49

    adey49 Member

    Yes that's what I thought, but his argument was that any moisture that does get through to the top of floorboards then has nowhere to go.
  4. KIAB

    KIAB Well-Known Member

    Honestly don't think you will have any problems with moisture,if you have good airflow.
    CGN likes this.
  5. adey49

    adey49 Member


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