[Strawbale] moisture

Tue Apr 12 09:30:30 CEST 2011

Hello Nikolay and others,

In our bathroom, we used a clay stucco and added an additive from my supplier of ecological materials called Tierrafino Fix which makes it more resistant to water; when becoming wet, it doesn't start to become soft immediately. But it still can when more water has touched the wall.
In our experience this worked very well, we haven't had any problems in 3 years now!
I expect the breathability will also go down a bit because of this additive.  This additive is made of cellulose, alcoholester, kieselgur, silicats, clay minerals and water and a minor fraction (0.1%) synthetic means for conservation. It's a liquid and a bit transparent substance. 
It's probably hard too get outside the Netherlands, but maybe this info helps to help you looking for comparable additives or make sth. yourself.

Lime is not only used at the exterior because of the damp-openness, but even more because its water-resistancy. I wouldn't know which material is more dampopen - lime or clay stucco. I guess this can vary quite a lot depending also of the exact mixtures you use for the clay (% of sand, % of clay etc.).
Regards, 
Rob Gort

  ----- Original Message ----- 
  From: jonas kacerauskas 
  To: European strawbale building discussions 
  Sent: Tuesday, April 12, 2011 8:17 AM
  Subject: Re: [Strawbale] moisture

  Hello again dear friends,
  I want to specify one important moment for all of us: all the time from different sources i was achieved information that lime plaster is more "breathable" than clay plaster, whats why i was tought to put clay plaster on interior and lime on exterior..the last time i saw this in UK in the library built by Amazonails...so i am very suprised about Andrew information...
  best regards:)

  2011/4/8 Andrew Morrison <Andrew at strawbale...>

    You're welcome Niki and you are on the right track to start off with the detailing fully understood. As Derek said, be sure to pay attention to all the details in creating a continuous air barrier. Some common places of concern are around holes in the plaster (electrical outlets and switches, ventilation gaps for the sauna, etc.), the transition from one surface to another like from the wall to the ground or ceiling, and from different materials, like where the plaster meets an exposed post or beam, and at window and door openings. Attention and detailing here is well worth the time and effort. Good luck with your project!

    Andrew 

    On Fri, Apr 8, 2011 at 11:59 AM, Nikolay Marinov <nikvesmar at gmail...> wrote:

      Thank you guys,ery 
      this is very important issue for me to get deeper in this topic. Precise detailing from the beginning is really right way for the solution. That's why I wanted to put this discussion.
      Also I would like to make few experimental walls and take samples after some period, but that is a long process. 
      Thank you for the replies and recommendations.
      Your support is really important for me, thank you deeply.

      Niki

      On Fri, Apr 8, 2011 at 8:43 PM, Derek Roff <derek at unm...> wrote:

        I agree with Andrew, that the relative permeability of the interior and exterior plasters is an important consideration in very damp situations like saunas and bathrooms.  I'd like to add that very careful construction detailing is probably even more important.  Research by the Canadian Mortgage and Housing Corporation (CMHC), an agency of the Canadian government, showed that having a continuous air barrier was very necessary to avoid moisture problems within the walls, regardless of construction method.

        Tiny cracks, holes, and seams that allow air movement into the walls will transport a lot of moisture with them; that moisture will be concentrated at a few spots, and condensation within the wall is very likely.  This can easily cause mold and other microbial bale decay.  A small break in the air barrier may transport more moisture into the wall than the diffusion through several square meters of plaster.

        Build carefully, and if possible, check for air gaps and leaks before putting the sauna or bathroom into service.

        Derelict

        Derek Roff
        Language Learning Center
        Ortega Hall 129, MSC03-2100
        University of New Mexico
        Albuquerque, NM 87131-0001
        505/277-7368, fax 505/277-3885
        Internet: derek at unm... 

        --On Friday, April 8, 2011 10:02 AM -0700 Andrew Morrison <Andrew at StrawBale...> wrote:
        Hi Niki and Jonas. I would be careful using a material like clay (earthen plaster) on an interior surface and lime on the exterior. Keep in mind that clay allows for more movement of vapor (is more "breathable") than lime. This means that one can transport say 1 measure of vapor into a bale wall through the clay plaster while only allowing for .75 measure to move out through the lime in the same time period. This means that excess moisture can get stuck in the bales.

        I have a wet sauna here in the states made of straw bale walls. I used lime plaster on both sides of the walls with a lime paint on the interior. After a sauna is completed, we open all of the ventilation ports and through an extra log or two into the fire. This drives the moisture through the vents and walls and dries things out with the dry heat of the fire. It's very successful.

        Andrew

        On Wed, Apr 6, 2011 at 8:46 AM, jonas kacerauskas <jonaskacerauskas at gmail...> wrote:

        Hello Nikolay,

        Here in Lithuania 4 years ago we have built straw bale bathhouse (like sauna, just with a lot of moisture - we call it russian sauna), where we use simple clay plaster about 3 cm. on interior wall and from the incident water protect with wooden plankets (there is natural ventilation inside). On exterior we did lime plaster - till now everything works fine. tadelact is quite expensive way and not needed way to deal with it. As we saw its enougth just clay plaster to deal with humidity and ussual you need to protect just several places from the direct water and were are a lot of ways to do it:) 

        best regards

        2011/4/6 Nikolay Marinov <nikvesmar at gmail...>

        Hi everyone,
        I would like to ask you for advice and share your experience about preventing moisture, penetrating into SB walls from bathroom, and other spaces with high humidity level.
        What kind of layers and finishes do you prefer to protect your wall if not using conventional waterproof materials.
        I know few techniques as: Tadelakt (good water barrier but time consuming); Double skin wall with ventilated space between,glass on the wall, but it would be nice to share a trusted and working in time method that builders and designers like you prefer as solution.

        Thank you in advance for you opinion.

        Have a nice spring sun.
        Niki

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    Consultant, Teacher, Inspiring Change

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