Go to Forum Home Building Design Airtightness of earth plaster

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    • #31485
      Anonymous

        On another list, there's a report of a blower test on an intended-to-be-passivhaus that [so far] failed to achieve the desired airtightness result (n50 of 1.2 and 0.95 instead of 0.6 ). The problem is attributed to air leakage through earth plaster. A plastic sheet sealed over the plaster inflated when the blower was run. Admittedly there was only 15 mm of earth plaster present at the time.

        Does anybody know whether this is to be expected? Is it practical to use earth plaster as an air barrier? What thickness? Or is it perhaps some faulty technique?

        Cheers, Dave

      • #37935
        Nick Grant
        Participant

          I saw a beautiful earth plastered panel by Andy Goldsworthy once with really lovely cracks due to the shrinkage of clay.

          http://www.crescentmoon.org.uk/gold%20Clay%20wall%20web.jpg

          I realise that proprietary clay plasters may address this shrinkage issue to some extent (eg adding lots of sand) but clay does shrink on drying whilst gypsum expands.

          Quick Google of 'gypsum plaster shrinkage' showed up, a table of different plasters (had trouble pasting a link but plenty of stuff out there).

          Nick

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