We DON”T want to build our house out of two-by-fours and drywall. So what will we build it out of?
Last weekend we explored the straw/clay insulation technique at a workshop offered by the Driftless Folk School taught by the Robert Schulz and his wife Summer. Their own home is straw/clay and was featured in the April/May 2010 Mother Earth News
There is something so elemental about this kind of wall. Its hand-smoothed surfaces create a soothing and timeless sense of place. Are you in ancient Babylon, on Tatooine or (as we were) tucked into a quiet valley outside Hillsboro, Wisconsin?
Straw/clay infill, as the course description explained, is a great option to insulate anything from a small outbuilding to your home. You can do it yourself. You can use local materials. You can create a healthy, safe wall. If you are interested, try to find someone giving workshops near you so you can get your hands in this stuff and see for yourself how simple and satisfying it is to make.
Robert let us practice on a wall in his blacksmith shop. Working with a handful of inexperienced people ranging in ages from just over one to just over 60, we insulated a wall in an afternoon.
There are books out there that can advise and inspire (and I’ve listed several Robert recommends below), but you really need to find a workshop or a mentor to get the feel for the materials and to grasp how exacting and yet forgiving straw/clay can be.
We started by mixing the slip, which is clay and water combined to the consistency of heavy cream. There is a lot of clay out there in the world, and you may have just what you need near at hand. The clay for this project was dug out of the hill behind Robert’s barn.
Using a ratio of about 2-1/2 gallons of clay slip for each half bale of barley straw, we coated each straw strand in a process that resembled tossing a giant salad. A hollow straw is preferable, making barley a good choice. One person splashed the slip onto straw piled on flat surface. We used a couple of sheets of old plywood. Then as many as four of us tossed the hay with pitch forks till every strand was lightly coated. The straw didn’t look wet, but if you squeezed it in your hand, it felt damp.
When a group is working on straw/clay together there is constant feedback from those who are packing with those who are mixing. “This batch is perfect!” “Make the next batch a little dryer.” That results in a custom mix that is just right.
With an existing wall cavity, still open to the inside of the building, Robert used pieces of scrap wood to create a frame about a foot high.
Then we picked up handfuls and pushed it down into place with our hands, taking extra care to make sure the stiff mixture was pressed into corners and any irregular spots. How tight you pack in the straw/clay is something you determine by feel rather than sight.
This is a job that one person can do, but it is a prime example of “Many hands make light work.” Shared tales, birdsong and joking and laughing went into this wall along with straw and clay. If it were my own project, it would probably include harmony singing and listening to recorded books.
Also, the next time I do this, I will wear rubber gloves. Clay really sucks the moisture out of your skin. It sucks the moisture out of everything, and that is what makes it a marvelous substance for this purpose.
Though the final curing can take weeks, it is really only minutes before the material is dry and firm enough to remove the wood form. Then that same board can be tacked on higher up as the wall grows. An exterior wall at this point would need to be covered with layers of clay plaster, and an interior wall in a house would also need several more coats to create a finished surface, but Robert plans to leave the straw/clay exposed in his shop.
Straw/clay is an amazing material – simple, clean, easy. I can hardly wait to try my hand at this again.
Some Valuable Books: