The post and beam style frame is going up. The windows and doors will each hang between two of these 90x90 posts. Notches will be cut in the bales as needed to recess the posts so they will end up fully enclosed in the bale and render walls.
We have done quite a bit of experimentation with our local clay soils to find good render ratios. (And found animal prints, both wild and domestic, in most trials before they dried) Up the hill at the highest point of our property is a patch of beautiful red/orange clay soil, it colours the render mixes delightfully, but I couldn’t come up with a recipe which made a strong render mix from it. Just behind our building site however, is large area containing huge chunks of dense blue/gray clay with very little else mixed in.
We have found a fabulous earthen render formula with it, but first we had to get the clay into a useable form. The two main methods are:
Dry and crush to powder
Soak until mushy
We had heard of folk drying out chunks of clay then running them through a tree mulcher to get clay dust, but frankly, it is easier to keep things wet here than to dry them out, so we hauled up some old baths, filled them with chunks of clay, and after about 3 days they had re-hydrated to a lovely clay goop. This soft wet clay is the foundation of our render.
Earthen Render Recipe for coats 1 and 2 on our straw bale walls:
1 bucket of hydrated clay
3 buckets of fat/brickies sand
1 cup of wheat or rice flour (mixed with water into a glue paste)
1 bucket chopped Straw
more water as needed
This quantity fills a wheelbarrow. we make a 3x batch when mixing in a bath.
Here are some other ratios we tried and rejected:
1st and 2nd coats:
3:1 RED promising but brittle
3 scoops fat sand
1 scoop orange clay
1 scoop straw scraps
1 scoop water
3.5:1 RED slightly dusty
3.5 scoops fat sand
1 scoop orange clay
1 scoop straw scraps
1.2 scoop water
4:1 RED too dusty
4 scoops fat sand
1 scoop orange clay
1 scoop straw scraps
1.4 scoop water
3.5:1 GRAY slightly dusty
3.5 scoops fat sand
1 scoop gray clay
1 scoop chopped straw
1.2 scoop water
1/10 part rice flour
4:1 GRAY dusty
4 scoops fat sand
1 scoop gray clay
1 scoop chopped straw
1.5 scoop water
1/10 part rice flour
Top coat we haven’t decided for sure yet, but all our trials using the gray clay and hydrated lime ended up cracking and/or drying brittle, so we finally left the gray clay out entirely and have just been using the red clay for its colour. Here is our most promising trials using builder’s hydrated lime soaked in water for at least couple of days to form a putty:
2 part lime putty
1/2 part red clay
8 parts sand
2 part sawdust to reduce cracking
1% linseed oil in increase water resistance
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