Foundations

Your containers are going to sit on footings. Footings are the part of a foundation that is dug from the ground and filled with rebar, inbed points and concrete. The footings need only be placed at each corner of each container. The acceptable size of a corner footing is 24"x24" and 16" deep. Where two containers are joined the footing underneath that point should be 36"x36" and 16" deep. At any point that the structure must be supported with an internal column you must support the point load with another 24" square footing.

This use of footings as opposed to perimeter wall or slab foundations is one of the major cost savings gained by using containers. I hired an architect to design my footings because city inspectors and plan reviewers like to look at blueprint drawings with an architect's stamp. Otherwise I would have foregone the cost (about $800.00) and done my own drawings on Corel Draw. When your working on a project that doesn't conform to prescriptive building methods its best to hire this kind of work done for you, if you show up at the building department with stamped plans they don't look at you like your some wacko. Trust me its better to buy your credibility on the cheap this way than to climb over the hurdles that a plan reviewer can demand.

A word here on terms:

#4 rebar (the kind you want to use in these footings) is that stuff that looks about 1/2" thick. Your going to want to form up two squares per footing about 8" above one another and at least 3" clear of the soil.

Inbed points; 3/4" Threaded stainless steel rod with a 1/2" thick 4"x4" steel plate attached at the bottom with a nut. The rod will stick out of the finished concrete and allows you to bolt another steel plate the same size onto the top of the footing. When the containers are placed on the footing this will give you a place to weld the container to the footing. Where two containers come together use two rods and make the plate 4"x8".
(This next part is comes to you as a piece of hard earned wisdom.) This weld is what makes the structure permanent as opposed to a temporary structure. This is important when an appraiser gives you the fish eye and says it just a mobile home and not a house. You will be able to point at the weld and the fact that the electrical meter is mounted on the container and not on a separate pole and say with confidence that its a permanent structure. Conversely if the city inspector is giving you grief about your project (because you didn't pull permits) than you can not weld down to the inbed point and claim its a temporary structure (like a mobile home) and you don't need a new house permit. (Always get the footing permit and have it inspected before you set the containers. This way you can choose which way to go when your deeper in the process.)

Concrete: You might not realize that you can now buy concrete mixed on site in just the amount you need buy calling a short load service. They have a special truck that carries the raw mix materials and will feed it down a shoot into your forms. This is a lot less work and expense than renting a concrete pumper truck and having to deal with a redi-mix truck. The redi-mix trucks usually won't cross your property line for fear of getting stuck and they want you to buy minimums that are going to be more than you need. A short load truck will pull right up to a dry site and save you these problems.

I trust that if your getting into a project like this that you can accurately read a measuring tape and know what a framing square is. In addition to these a good quality laser level will keep you out of trouble. If you need to build forms to make your foundations level at both ends build them four times as strong as you think they need to be, concrete is heavy and you don't want to clean up a mess if the form breaks while your buddy's stand there laughing there asses off, seriously.

This has not actually happened to me but its been close.