Ok, now I'm home at the computer. Since sometime in May I have been treating this floor like it was a standard plywood subfloor. I just figured if there was any damage I would cob it over. I can say that it is very durable and I would probably use this method again but improve on my execution. I'll try and answer questions that came up and explain my logic in this project. I gathered all of these cans from local restaurants over several months. I just approached them and told them I could use them for a building project and weekly I would come by and pick up a garbage bag full. With my floor, a couch, or bedposts or something heavy with legs would probably create a depression over time but I would bet that a 3 inch cob layer with an oil-hardened finish would stop that from happening with typical floor use. I think the trick in using cans in this way is to tamp and compress a lot before the floor is completely dry. If I had done this (which I did not), the floor would be in much better shape than it is. My theory is that if you dont give the cans anywhere to go then they wont move. Essentially this means tamping out any and all air pockets. At most I am able to work on the cabin 3 days a week during decent weather, so I missed the ideal windows of tamping because by the time I would get back the floor would be too dry. All I was going for anyway was a level-ish surface to work on so I could complete other interior projects in the cabin more easily. All in all my reasoning for this method was that I would either have to purchase more lumber and frame in a floor or I would have to mix up a ton more cob to make up for the volume that the cans take up. So, if we accept ideal building conditions as a given; that is -quality clay, plenty of straw, plenty of help, a few screes, a laser level and a reasonable timeline then I think this method works very well. Also, make sure the cans are clean because there were tiny little ants early on in the season. I washed all of these with soap and water but it seemed apparent that I missed a few spots.
In some areas I set the cans too high and the top layer of cob was too thin. This let to cracking but still it was functional as a floor. In other areas if the cans were set too high then I just lowered them by beating them down with a hammer. It was the quickest way, then I just poured more cob and leveled it of best as I could. In one particular area I beat the cans too much and there ended up a large depression -still fixable however.