Sealed Membrane in PWF Floor in PWF Foundation

  • 08 Sep 2016 3:39 PM
    Message # 4234838
    Pam Warkentin (Administrator)

    I am a private homeowner in the Okanangan, building our house, as we can afford it, on a limited income; we are hoping to build with a PWF floor.   I am referring specifically to a problem regarding the 6 mil poly on the PWF wood floor, not the PWF walls

    Having a PWF Floor in PWF Foundations is recommended over concrete because concrete has pores that can hold moisture.  However in the PWF floor system, it requires that the 6 mill poly be overlapped and NOT sealed so that, in the event of a plumbing leak, the moisture has opportunity to escape.  The new radon code requires that the 6 mil poly be sealed so as to prevent radon gas from seeping out.

    1. This, in my mind, is a conflict in the building code and I can not seam to find an answer online as to how others have solved this issue.  Has this been reported to whoever makes changes to the BC/National code and has there been any solutions/suggestions to this problem?  Do we still just overlap the poly on the floor or do we seal it? ( I can't find anything in either the BC Code or the PWF books addressing this issue, just that each must comply with the other.
    (posted on behalf of a homeowner)


    Last modified: 08 Sep 2016 3:43 PM | Pam Warkentin (Administrator)
  • 08 Sep 2016 3:41 PM
    Reply # 4234840 on 4234838
    Pam Warkentin (Administrator)

    Install a fire rated, membrane with a Drainjer in low spot of gravel bed.

    Problem solved


  • 08 Sep 2016 3:41 PM
    Reply # 4234841 on 4234838
    Pam Warkentin (Administrator)

    Should verify the assumption about overlapping the poly. I would have thought that the plumbing is installed in the subgrade below everything not above the poly. Installing the Drainjer would be an extra safeguard in the event of a plumbing leak within the building. 


  • 08 Sep 2016 3:41 PM
    Reply # 4234843 on 4234838
    Pam Warkentin (Administrator)

    Yes you need to seal the membrane. Here would be an ideal situation to include an active system with sidewall ‎venting as part of the. Design of the home as a system. One of the prerequisites is they must be installed on very well drained soil and contractors forget that they must control vapour intrusion into the PWF foundation boards otherwise they deteriorate rather quickly and the home does not have the life expectancy that the owner expects.

    Active radon system in PWF home usually only requires a small radon fan with a central draw point. This will prevent radon entry if a sealed membrane is utilized and lower and dry out any vapour intrusion that occurs under the floor. If a intermittent spill is the concern install a floor drain through the membrane with a trap seal primer if septic system and sanitary drain is below the level of the floor or install a sewage ejector system with a floor drain where the pit is sealed to membrane and the floor drain is sealed to membrane. The sewage ejector system is normally required where there is future plans to locate a washer dryer in basement anyway. 

    Washing machine back up is the most common intermittent flooding ‎issue that I know of as a plumber. 

    I hope this helps! 

    Yes you need to seal the membrane.


  • 08 Sep 2016 3:42 PM
    Reply # 4234844 on 4234838
    Pam Warkentin (Administrator)

    Not too sure what would be the use of a vapor barrier if it’s not sealed properly.


  • 08 Sep 2016 3:44 PM
    Reply # 4234848 on 4234840
    Pam Warkentin (Administrator)
    Pam Warkentin wrote:

    Install a fire rated, membrane with a Drainjer in low spot of gravel bed.

    Problem solved


    Note: information on Dranjer's can be found on their website: www.dranjer.com

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