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?
...Mixing clay slip
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.
...Tossing a giant straw/clay salad
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.
...Temporary frame to fill in with straw/clay mixture.
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.
....Nature's styrofoam
Straw/clay is an amazing material – simple, clean, easy. I can hardly wait to try my hand at this again.
Some Valuable Books:
Econest: Creating Sustainable Sanctuaries of Clay, Straw and Timber
The Natural Plaster Book: Earth, Lime and Gypsum Plasters for Natural Homes
Categories: Uncategorized
Digging in the Driftless 
This is a fantastic way to do insulation. Having never experienced a Wisconsin winter (I’d love to though) I can’t really imagine what kind of temperatures this insulation is supposed to be able to tackle. I’d like to try this back in the old country (Sweden) and we had a month of -8 degrees (fahrenheit) this winter. I wonder how thick the walls would have to be?
I’ll try to find more information but thanks again for sharing this! It’s great to get inspired by people like you!
Thanks for your comment.
My brother, as it happens, just spent last winter in Gavle, Sweden. Comparing notes, his winter had longer nights and a bit more snow, but was no colder than here.
So, I can tell you that the teachers at the straw/clay workshop live in a house they built of this material. They made their walls 12 inches thick, and seemed very pleased with the insulation value.
Their house had a wonderful feel inside. The straw/clay was plastered over and hand smooth, but not machined smooth. I like that kind of surface very much.
Good luck in your research and future building projects.
Denise
I have a 5 year old home and would like to use straw/clay to insulate the walls. Contrary to the extreme cold, I live in Central Texas where we experience extremely HOT summers. I would like to make this a family project. I think my 4 children would enjoy the hands on experienceand learn the value of natural resources. Before I knock the sheet rock off the wall, I would like to get you opinion. Do you recommend it get done to a newer home? And, can I do the second floor?
Thanks
Ed
I don’t feel expert enough to answer these questions. I have tried my hand at the process at a great workshop in Wisconsin and fell in love with the material, but you need to talk to someone in your area who has experience with straw clay to see how it will work in Central Texas.
Good luck, I hope it works for you. It’s a wonderful, natural building material that looks and feels great.
That much I do know,
I have just read an article that describes retrofitting houses with straw bales. It is aimed at the UK housing stock but maybe you can find some of the answers here Ed.
http://transitionculture.org/2011/07/05/the-potential-of-natural-materials-in-retrofitting-our-homes/
Thanks, Joanna. That is very interesting. I think the article is right that it would take the right kind of structure and the right kind of owner, but it could be very possible to retrofit a strawbale exterior. I love that thick insulation and deep-set windows. I’m sure it can be a great improvement.