Mud is magic. Mud is fun. Mud can also be quarrelsome.
Don’t get me wrong, I love earth plasters. I want all new strawbale homes to be wearing them. They make the most beautiful walls I have ever seen. The colors are gorgeous and incredibly varied. The walls feel soft and homey. Earth plasters can be rustic and undulate with the bales, or create smooth walls with even curves and a polished finish. The materials are cheap, easy to come by, and healthy for the environment. Earth-plastered walls breathe like living beings, protecting bales from moisture damage by exhaling moisture instead of locking it inside. Mud is a blast to work with, can be extremely durable, and is easy to patch and repair when necessary. (Durability sidebar.) I highly recommend it.
Sometimes earth plastering is so simple it is astonishing. Friends in Arizona and California have found that the earth beneath their strawbale cabins had the perfect proportion of clay and sand. All they had to do was add water, one also added a bit of chopped straw, and voila! Beautiful plasters that didn’t crack.
So why do I quarrel with my walls? Well, I don’t really (mud is always right). But I have had several long, drawn-out head-scratching sessions while questioning my walls (“just why are you doing that?”) Working with mud keeps me on my toes and forever curious. (Whoops sidebar.)
The simple truth is, mud will never be a standardized material like cement. Each batch of dirt is different and has its own personality. (Clay sidebar.) Earth plasters have a slower drying time and must be built up more slowly than cement. There are very few people with big machines to spray it on (and even fewer who have enough experience to be beyond the experimental stage). If you want smooth walls that don’t reveal the shapes of the bales, you are probably looking at a lot more labor and time. And then, with each new batch of dirt, there are the potential surprises. In this country, we are only beginning to recover the lost art of earthen plasters.
It used to be different
Information from this section comes from research conducted by Susan Barger and was published under the title “Investigations Into The Durability of Plasters, Part One: Initial Materials Characterizations and Correlation With Oral Tradition.“
A hundred years ago in New Mexico, each village had its own location for the best plaster dirt. Adobes could be made from virtually any earth, but the plaster dirt was special and was often carted, if necessary, to the building sites. Its properties were known and loved, and the techniques for working with that particular dirt were passed down from mother to daughter in the tradition of the enjarradoras.
Unfortunately, much of that plastering knowledge was lost with the arrival of the upstart newcomer, cement. The source sites for the dirt are remembered by few. Carole Crews, Cornerstones (the folks who restore the old adobe churches in NM), and others have done a lot of research into the old ways. Susan Barger has some fascinating interviews with older folks who remember participating in the plastering as kids. She also analyzed old plaster samples, looking for clues to what makes a durable mix. Ms. Barger found the chemical reactions in mud plasters to be so complex that they had more questions than answers at the end of the research. Clearly more is needed.
But even if we understand how to work with one particular dirt, the fact remains that the soil of Santa Fe is different from the soil in Oregon. In fact, the dirt under my feet may be completely different from the dirt 30 yards away.
So What Does This Mean?
First of all, relax. Earth plastering is easy. Once in the mud, many of us feel we are remembering information our cells have tucked away for us long ago. Getting in the mud helps us access that knowledge. I had a similar experience in one of Robert Laporte’s timber framing workshops. After struggling with the chisels for days, feeling clumsy and awkward, I experienced something clicking in, and all of a sudden I was handling that chisel like I’d been doing it for years.
But we shouldn’t have to rely completely on intuition and memory of past lives! Or whatever it is that happens in those magical moments. So here are some tips avoiding potential problems and keeping the fun in the mud.
First, ask yourself these questions:· How much durability do I want and need? Is it a meditation hut or a conference center? Do you have ten kids?· How much time do I have? (If you need it finished this week, call the local cement stucco crew. Earth plasters take longer. Plan it into your schedule. Prioritize the areas that need to be finished first. Prioritize the exterior if winter is coming on. Interiors can be done in cold weather, but see sidebar cautions about plastering in winter.)· How much money can I put into this? If you are on a tight budget, get your friends to help you and/or do workshops. The materials are dirt cheap and the labor will be free. If it is a big house, consider bringing in an experienced person to show you the ropes and help you figure out the mixes. If you want to hire a crew and want smooth, polished walls, expect to spend more than you would for cement stucco. If anyone out there knows how to make it less expensive, write an article and let us know!
· What do I want the finished walls to look like? It takes more labor and materials to create smooth walls out of lumpy, undulating bale walls. If you like the natural curves, keep them!
· What materials do I feel comfortable using? The mining of materials—even dirt—is harmful to the earth. Look first at what is around you, and what friends have available on their lands. Try to use materials that have the least impact to create the plasters you want and need. We will all make different compromises—make sure yours feel ok to you. And get creative if compromising doesn’t work for you. Perhaps you’ll discover something that will help us all out!