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Concrete Ring Foundation Condensation

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  • Concrete Ring Foundation Condensation

    I have a house on concrete piles and am currently installing underfloor insulation and putting down a vapour barrier. What I have noticed by being under the house is that the concrete ring foundation on the south side only is wet with condensation. I'm baffled as to why the condensation is only on the south side and not the whole way around. The floor joists and perimeter bearer on the south side also look like it has absorbed some moisture. The vents are not blocked but it looks like the house could do with a few more vents according to Branz. The house is on a level section, probably built in the early 1900 with Stucco over weatherboard. Any help/advice would be much appreciated.

  • #2
    the most effective mitigation of subfloor moisture is polythene to the subfloor area as neatly as possible to edges and taped seals and taped to piles. make sure the ground is level or sloping to allow run off if there happens to be a ingress from surface is some part so as to not trap water with ponding. If there is a reasonable slope then unlikely.

    The reason south is worse is because this is cold side and the most likely to form condensation. It may also be the low end? or less height which traps moist air?

    Moisture is a product of water evaporation and ingress into sub-floor area vs drying by ventilation. If ventilation isn't adequate reduce the moisture load with polythene and you stop evaporation into the space. I it simply remains where it does no harm under the polythene. If house has T and G flooring it can be a big source of internal condensation issues.