Shipping Container Building Construction Basics
We get a lot of inquiries about shipping container buildings, so we'll cover some basic (and important) information about how these buildings are constructed. First, we get a lot of calls and e-mails suggesting we go to this web site or that web site because they have "plans" available. The plans that we've found on the web have little or no information about how to structurally support the fanciful designs, or any of the construction details (connections, roofing materials, wall cross sections). Building a shipping container building is not as easy as drawing a picture of what you think would be a nice structure, there is a significant amount of architecture and engineering involved.
Shipping containers come in a number of different sizes, most common is the 8'x8'x40' unit. There are 8'x9 1/2' x 48' units coming on the market, which are much more suitable for buildings because the height will let you hide duct work, electric, and plumbing above the ceiling.
There are a number of companies that sell used shipping containers. The shipping lines get rid of the containers once the period of depreciation is over no matter what condition they are in. Generally from what I've seen the condition of the shipping containers are pretty good. The cost is in the $2,000 to $2,500 range per container here in Atlanta, GA. It may vary depending on where you are.
Unfortunately, there is no "standard" shipping container design. There is an ISO standard for their load carrying capacity, and that has resulted in most containers being pretty much the same regardless of manufacturer. The containers are generally made from steel corner posts, steel side rails top and bottom, and corrugated steel sides. The floor is steel sheeting with hat sections stamped in it, covered with sheets of plywood. The plywood is treated for insects, and smells pretty nasty. In any building, you will want to remove the plywood.
The containers do have a standard design at the connection points so that it is possible to tie them down on cargo ships, trains, and trucks in a uniform manner. The loads are all carried through these points, which makes construction much easier.
The architectural layout has to comply with Codes as far as egress, room sizes, aisle widths, railings and so on. So, the Architect has to layout the containers in such a way that the space is in Code compliance. Once that is accomplished, the design has to take consideration of interior finishes, roofing, mechanical, electrical and plumbing.
When I was in Central Asia with the Air Force, and in the building we designed in Atlanta, the walls of the containers were furred out, and insulated. This gives you the room you need to run the necessary electric. In the Central Asia we used split system HVAC units for heating and air conditioning, and the plumbing was non-existent. For bathrooms we used outhouses (sani-john type), and sinks and showers were in a nearby tent. While you can use split system units here, you can't expect people to use an outhouse, or shower in a tent.
So, for the house in Atlanta, the HVAC was on the second floor, and duct work was left exposed in the ceiling. The bathrooms, and kitchen were put to the back of the house. If you use the high cube containers, it solves a good part of your problem with pipes and ductwork.
For the roof, the containers are supposed to be water tight, but in time the roof of the containers gets beat in, and water doesn't run off like it should. A roof has to be put on the buildings. In Central Asia, the contractor stick framed gable roofs. In Atlanta the architect used a flat membrane roof. I personally like gable roofs because they are less prone to leakage than flat roofs, and require less maintenance.
Once the architecture is done, you need a structural design. Since there doesn't seem to be any standard design, with exception of the connection points, it presents a problem when structurally engineering buildings made from these. See the section of this website titled Structural Engineering of Shipping Container Houses for information on our approach. Basically, we measured shipping containers in the field, and then built a model by using steel sections that were slightly smaller than our measurements. We have not found any definitive engineering reference on shipping container building construction, in the future we plan on contributing articles to engineering publications covering this issue. As this method of construction gets more popular, we may see texts published on the structural design methodology, but until then we have to work our way through this.
Remember, loads need to go through the connection points. This allows you a lot of flexibility, and makes foundation construction much easier - you can transfer loads to foundations at the corners of the container.
Permitting the structure can be difficult. In the house we designed in Atlanta, there were repeated meetings at the City with different officials. You are attempting to build a non-standard structure, and expect a more in-depth look at your plans and application. Watch out for zoning and covenants, check those issues out first before you start. If you can talk to the building officials before you start, do so.
Construction is fairly easy, except in residential construction you will run into issues with the skills and capabilities of the labor force. You have to unload the containers and place them with a crane, which is unfamiliar equipment to many residential contractors. There is significant ironwork required as you cut out the sides of the containers and have to weld in pieces of steel to reinforce the containers after they have been cut into, and that can be a problem for residential contractors also. Depending on the workload in your area, it may be difficult to find a commercial contractor interested in a small shipping container structure.
The sequence is pretty basic - you pour the foundations first. Then you haul the containers to the site, cut them as needed, and lift them into place with a crane. Additional steel may be required depending on how you cut up the containers. After the containers are in place, the additional steel is erected, and the containers are connected, you then can start the other more conventional parts of construction.
One issue to look out for is welding - if you are building a residential structure, and welds are being used to add bracing or tie the structure together, this could lead to problems if the welder is not qualified to the task. The welder should have AWS certification, and I recommend having a testing firm examine the welds.
- The design fees for a shipping container building will be higher than conventional construction.
- A lot of sites on the Internet make the design look very simple, because the "designs" they have are not complete by any manner, and it doesn't appear that they've actually been constructed in many cases.
- Permitting might be difficult, plan for more effort to get the building permit.
- It's important to get a qualified contractor, and be aware that welding skills are critical.
Oh, and don't forget to call us if you need design services!
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