[Cob] cob mortar/filler

[Frederick Eugene Grinder III]

Hi everyone,

First, thanks for making this list so great, and many thanks to the
moderator!

I've got a small cabin whose walls are made of rough-cut lumber planks, run
vertically and nailed to a frame, like a barn?.  On some walls, the gaps
between the planks are covered on the exterior by strips of wood (name for
this style?), but on other walls you can see right through the gaps.

My plan is to fill the gaps with mud.  We have lots of clay on site, and the
results of a few test areas look promising.  I'm considering different
additives to the soil, like sawdust or sand.

Has anyone here tried this?  What additives are used, and in what
proportions?  I realize proportions are very much dictated by soil texture,
so, what techniques can I use or what signs can I look for to determine
proper proportions?

Thanks!
Gene