The foundation is one of the few things that I needed to get professional help in designing. I wanted to make sure it was done correctly and safely, especially when the internal walls were going to be completely removed. After looking high and low for an engineer that could help me with shipping container construction, I found George Runkle at Runkle Consulting, Inc. He has a lot of experience in this area, and has even developed his own computer programs to analyze the structural integrity of shipping containers when they are modified. These programs were specifically used on my cabin to spec out the steel box beams that would be welded to the top of the cabin for support when the walls were cut out.
The first foundation George designed was a series of piers to support all of the container corner blocks. Each pier had a metal plate on top with welded rebar embedded into the concrete pier. When the container was set into place on the foundation, the corner blocks could be welded to the metal plates. This would definitely be the most cost effective foundation, and would also be the easiest for the do-it-yourselfer to build. In fact, most of the container cabins you see online use some sort of pier foundation. Unfortunately, I really don’t like the look of pier foundations, and have actually had some trouble with them in the past.
I then asked him for a foundation with 1′ thick walls in the front and back to support the containers. To me at least, this was much more aesthetically pleasing, and gave the cabin a more substantial and rugged appearance. I also have the option to easily enclose the foundation with treated plywood on the sides if I ever wish to. This could give me a bit more storage space protected from the weather if I ever need it.
The two center piers are to support the floors when the four inside walls are completely removed. The piers are 6-8 inches below the height of the outside walls, and will be shimmed with treated lumber to the correct height when the containers are in place. The top of the containers will be reinforced with two 6″x3″x20′ steel box beams welded to the containers.