Can cob be water proof? I want to build a small house boat to homestead on the river bank and on top of the river? If needed I am willing to use on partial home. I would like to create an all or mostly natural house boat.
I wouldn't use cob for boat building. If you were looking to do interior walls natural, wattle and daub might be a good idea. Cob is not waterproof, but will soak up moisture and crumble apart. As previously mentioned, cob is also very heavy and not ideal for floating. You can make water resistant clay plasters and waterproof lime plasters called tadelakt, but I would stick to wood for boat building.