I live in central TN and want to build COB, i have tons of rock, i did a jar test and it seems i have about 40% sand and 60% clay in my soil, but its also filled with rocks of various sizes. Assuming I removed the larger ones (over an inch?) and kept the smaller ones, would I be able to build with this? I do not have access to heavy equipment.
Depending on the application of your cob, I would say you will be fine leaving modest-size stones in your cob. My native clay has probably more sand and gravel (after rocks are removed) than clay and silt. For mass building, the aggregate may even be helpful, and certainly does not hurt. For finish layers, of course, you want to sift out anything bigger than your intended thickness. For thermal cob in a RMH bench, the more rocks the better - they will increase the density and thermal performance, while reducing the amount of clay you need to process.
Location: Central TN
posted 1 month ago
Livable structures are the goal, so it would be safe and strong? Awesome