I’ve been enjoying the latest newsletter articles by Coenraad Rogmans over at House Alive!. In the article, Building with Sand, Straw and Clay, Coenraad talks about the many variations of the magical mixture of these ingredients. There is a spectrum of ratios that create different variations of these base materials. Including cob, light clay, wattle and daub, bale walls, bale cob, earthen floors, plasters, renders, and paints . Within each application one would use a different ratio for a particular result. Say for instance you are working on a cob wall with built in niches. Ianto Evans teaches about corbel cobs. Cob with long stocks of straw for added tensile strength. Another is light clay, a mixture of straw tossed like a salad with the dressing being clay slip, or watered down clay. Or for an earthen oven a sand clay mixture. You can see how versatile it can be!
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I want this southern wall to be mostly cob and earthbags to collect the warmth of the sun. Of course, it would be wonderful to have a pure cob wall, but time does not permit. And after all that’s slow! Here’s the thing though - It’s already cold. I’m pushing my luck with light clay infill. The light clay takes a long time to dry. Even in warm weather you should let the light clay infill dry for a couple of months before plastering. Cob too. It won’t dry in time. Basically, I’m after a wind break for the winter so I can work inside.
 

Light Clay Cram

It’s somewhere in between wattle and daub and light clay infill, but it not really either. I’m making use of my post and beam structure by nailing saw mill ‘waste’, known as mill ends, to the posts. This creates a good lattice for what comes next.

I made some light clay and let it sit out in the sun for an afternoon. The earth absorbed the excess moisture and the clay gets pretty tacky. I took a lump of light clay and placed the in between the open space between the mill ends and cram it over to the side. Packing and pushing. The lump of light clay fills the gap and hangs over the mill ends both inside and outside. I just kept doing that until the openings were full. Let dry in the feirce winds…

After a few days of sun and wind it was time to add mud. I tucked earthen plaster in the gaps and covered the light clay. The straw creates a good key. Now when I go back in the spring to add the infill plaster the wall is ready and I have a wind break for the winter.

This has got to be one of the quickest and low cost ways to create a wall. Rather than building up slowly this allows for the wall to go up first and then thicken up later. The wall is up. The materials were cheap. And the amount of human energy was moderate.

ECONEST: Creating Sustainable Sanctuaries of Clay, Straw and Timber by Paula Baker-Laporte and Robert Laporte.

Light clay, straw / clay, light earth or leichtlehm is a natural building material consisting of straw and clay, as you might suspect from the name. The straw is tossed like salad in a mixture of creamy clay slip. It is then stuffed in wall cavities surrounded by forms. As one coarse is filled and tamped the form work, usually a 4 x 8 piece of ply wood is removed and leap-frogged above the next ply. At the end of the day the forms are removed and the wall is allowed to dry, sometimes for as long as a year. When dry the walls are covered with an earthen plaster or wooden cladding. This material is used as an infill only; it is not a load bearing material. It is a great material to use in combination with timber-framing as Robert and Paula have illustrated in the EcoNest designs.