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The Eartha Madre Project

To contact us:

info@EarthaMadre.com

Mixing the earth plaster

After seeing and experiencing the look and feel of natural earth plaster we decided that it was definitely the perfect finish for straw clay walls.  The traditional use of mud plaster to coat and protect walls dates back a very long time and is found in almost all regions of the world.  Finishing our house with mud plaster when the house itself has been built with other renewable earth materials was a complimentary technique.

Experiencing Earth Plastering

Mud plaster ready for application

Since it was more than a year between the time we dug the foundation and the time we did the mud plastering, we were able to use the clay that came directly from our foundation trenches.  Having sat in piles for about 18 months, the rain and snowfall, along with the freezing and thawing process over the winter broke the clay down and made it the right consistency to use directly from the piles with only a simple sifting. 

One advantage of earth plaster in a natural, sustainable home is that the color of the plaster itself eliminated the need for any paint. This is good for the environment and reduced our construction finishing costs.  We didn’t add any colorants of any kind, in fact our only addition to the clay, water and sand mixture (aside from the a small amount of  shredded straw in the first coat) was about 12 ounces of linseed oil to each batch mixed in our mixer.  The linseed oil acted as an additional binder and really helped make spreading and smoothing almost effortless.

Earth plasters are very user friendly and fun to work with.

One of the most enjoyable natural materials we worked with was the earth plaster (which is also referred to as mud plaster and clay plaster).  Earth plaster is nothing more than sand and clay (with a small amount of shredded straw added in our rough coat) mixed together in the proper proportions to prevent cracking.  We found that mixing a water and clay slip to the consistency of a heavy cream, then adding sand until the desired spreading consistency was achieved provided and amazingly easy to work with plaster.   When mixed and applied properly, this plaster wall covering is hard, durable, and beautiful.  We even used  earth plaster on the upper half of the exterior walls because we had planned extended overhangs of the roof to protect the walls.  We’ve been living in the home for 5 years now and the plaster has been on the home for 7 years.  We have only a few places on the exterior wall that will require a bit of maintenance this coming spring.

The finish coat

Earth plaster can be applied directly to the straw clay infill (code permitting) however we wrapped the walls in chicken wire to assure good adherence and because our codes still require wire netting on the straw clay. The fibers of the straw create a very strong bond with the mud and the addition of the chicken wire was a minor inconvenience.  Our experience was that the mud plaster was extremely easy for us beginners to mix, work with and apply.  We found this is especially true for the initial coat, and for our home we accomplished applying the first inch + of mud to the walls just in the nick of time.  The day we finished the rough coat of mother earth’s “skin” over the entire house was the day the Rodeo Fire started less than 20 miles south of us.  Had our intuition not led us to starting the plastering when we did, our entire building would have been smoke damaged beyond repair from the thick smoke that enveloped our area for more than a week as the fire burned through.

Our “truth door”

In a natural green home such as ours, the wall finish is a major visual attribute to the overall look of the house.  Our earth plaster walls have a rich patina that is not possible with paint or even stucco.  They are mostly a smooth, flat finish however there is a certain quality to them that is unique and feels wonderful to the touch.  The material is breathable, unlike most paints and stucco and is ideal for straw-clay or straw bale construction in that moisture from within the walls can evaporate out.  Breathability is important in any wall system, and particularly important when building a straw-clay, straw bale or adobe home.  We included a “truth door” just off the front foyer to be able to show what is actually behind the smooth plaster finish of the interior and exterior walls.