Why make a stone using cob mixture as mortar? Part of our “barn/studio” walls are made from cob. We liked the process of mixing. We have fine, sticky red clay, lots of it, so we didn’t have to buy mortar mix. We wanted a natural, low cost floor. So instead of mortar or wood, we just scraped off to a serious hardpan, mixed up cob and our friend Jefferson Hubble laid stones in a cob mixture (sifted clay, sand, hay and a little lime). As it dries, we know the natural mortar will crack. Then, we’ll come back with a fine clay, adobe like paint and fill in the cracks and possibly saturate it all with linseed oil.