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Clay Finishing question from Uruguay

October 8, 2018

Spanish: Hola! tenemos una casa de barro en uruguay y nos gustaria saber mas sobre como tratan el barro y como dar un buen acabado! muchas gracias
— Carolina from Uraguay

English translation: “Hello! We have a mud house in Uruguay and we would like to know more about how they treat clay and how to give a good finish!”
—  Carolina from Uruguay

Dear Carolina:

Finishing clay or stucco can be considered easy or difficult depending on how much work you decide to put into it. It is always much easier to get someone else to do the work, such as a paid professional.  🙂

The outside of our tire bale house is stucco– a mix of concrete and sand and some chemicals to seal each layer of stucco.  We put the stucco on in 6 different layers. The product is from Sto Corporation (https://www.stocorp.com/  ) from Germany).   Applying stucco is like painting with peanut butter (mantequilla de maní).
The stucco is troweled on using standard concrete trowels. If you like textured walls, you can leave trowel marks.  (We like textured walls versus smooth walls.)
Each different layer has come kind of protectiveness to it and interestingly, each layer is a different color.    (To see the layers in Sto’s products and to understand their products before using them, visit https://www.stocorp.com/stucco-systems-us/  ).

The clay on the walls inside of our home was much easier since the clay is not the consistency of peanut butter.  Instead, it is like wet sand at the beach. However, we had to trowel the clay onto the walls one layer at a time.  Each layer could not be thicker than that of a credit card or less than 9.5250 mm thick.  Only 2 layers were suggested for our application. We also finished the clay with a product that helps to keep it from shedding. I think that product was a masonry primer.  A good stucco person would know the best product to use to keep the clay from shedding.  We used special small trowels for the clay application.
Smoothing for the clay walls inside was done with water in spray bottles and thick sponges. Spraying on the water and wiping the sponge in the horizontal direction. As the clay dries, you can always come back and smooth some more as long as the clay is wet. Since the clay has lime in it, chemical gloves are a must to wear when mixing or applying clay.

An interesting possibility when using clay is to make use of stencils in areas where you would like to be a bit artistic.  The layers of clay will have to be much thicker here to accommodate the stencils.

Since Uruguay can be a wet environment sometimes (Colorado U.S.A. is very dry), I suggest seeking the advice of an experienced stucco person there. They may have a much better opinion of the best products for your environment.

I hope some of this information helps your project.
Best wishes!

2 Comments leave one →
  1. Chip Brown permalink
    July 25, 2019 8:33 pm

    HI Folks! Wonderful to read of your adventures – I am particularly interested in your tire-bale home construction. We are recently retired from Wisconsin, relocated to New Mexico where we are embarking on an off-grid, tire-bale home construction. We intend to be self sufficient and will be working with our local community providing farm-to-school produce commodities, etc. If you are able, I wonder whether you might provide information about technical elements of tire-bale construction? Specifically, we must submit an engineering study to the State of New Mexico to obtain a construction permit using tire bales. Our engineer is having some difficulty finding information about the lateral strength of tire bales in construction applications. I would be grateful for any info you could share with us. Hope that all is well with you. Thank you so much! Sincerely, Chip (and Kimi)

    • July 26, 2019 3:18 pm

      Chip
      Review the document I am sending to you in email compiled by our P.E. to see if it can answer some of State’s questions. I have other files that I can provide also that might also help.
      Tire bales have been used in construction since the early 1980s. I don’t know of anyone or any government that has used them that would change their minds about using them–but I am not a P.E.
      The State’s question may revolve around using tires individually versus in a bale. Individually (pounding dirt into tires as in Earthship techniques tends to create laterally unstable walls. We have seen this personally in our designer’s house. Our walls DO NOT MOVE.
      Hope this helps.
      Hagars

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