basic container design – structural considerations

It seems like it’s been quite a while since I did a post about something relating to container architecture. Well, let’s rectify that right now.

Oops.

When designing a home constructed from repurposed shipping containers, one of the most important areas to pay special attention is structural. We can make containers look good all day long. A cutting torch, some bar steel, a few rain screens and some storefront and you’ve got yourself one archisexy container home. But will it stand up? Will it resist wind shear or rain/snow loads? Will it simply buckle and collapse due to a lack of pier supports? Hopefully the answer to these questions is no because you consulted a qualified architect/designer and structural engineer early on in your project to ensure your building is safe, structurally sound, beautiful, and functional.

“But why is this so important? Aren’t there a bunch of guys out there telling me that I can just buy a container and make my own home for pennies on the dollar?”

Yes, there are guys like that out there. I suggest running the opposite direction from them as fast as you can, preferably towards someone with real training and expertise in building construction.

would you rather live here, or (see next image)
would you want to live here?

 To illustrate this point, I’m going to rely on someone who has several container projects under their belt and one currently under construction. He also happens to be a structural engineer so he knows a thing or two about how buildings stand up.

George Runkle, with Runkle Consulting, Inc. in Atlanta, Georgia posted a sort of structural dissection of a shipping container a while back in which he used 3D computer modeling to simulate typical structural stresses and looked at the weak points of to container components. Here are some of those images.

image courtesy of Runkle Consulting, Inc.

This first image is an exaggerated view of the steel deflecting under loading. You can read a great description of what is going on here on George’s blog.

image courtesy of Runkle Consulting, Inc.

The image above is of a standard 40′ container under 40lb/sf live load and 24lb/sf roof load or 90mph winds, which would be typical for most residential areas on the east coast. As you can see, no red (failing) areas in the structure.

image courtesy of Runkle Consulting, Inc.

Now in this image we see some areas where the stress was too great and some members have failed. Though, in this instance the container was loaded to 50lb/sf or 200mph winds. This would be in the neighborhood of a CAT5 hurricane.

Both of the above containers are loaded “stock”, or without any modification. While these numbers are impressive and certainly make a good argument for container homes, at some point you’ll want to add things like windows and doors, so we need to look at what happens when the sides are removed.

image courtesy of Runkle Consulting, Inc.

Above you can see the container with sides removed as you might do if you wanted to join containers together or add large expansive openings. Under standard loading, similar to the first image above, you can see the container fails miserably. This is because a container is designed as a singular unit with all pieces working together to create that amazing structural integrity. If you remove parts of that system, the unit begins to fail under general loading. Those openings need to be properly reinforced and braced to ensure stability.

This is exactly where qualified architects/designers and structural engineers become so very valuable on your container home project. Because without proper design and engineering you could be putting your home and family at risk. The money you might pay upfront for design and engineering services is completely overshadowed by the benefit you receive from solid design and engineering of your home. I hope you’ll think about this post the next time you see some other website/blog touting all the benefits and money saving tips for “DIY” container homes without consulting trained professionals. While anyone can build a home for themselves with the right knowledge, tools, and equipment, you still need proper design and engineering to ensure your safety, security and investment.

Special thanks to George Runkle, of Runkle Consulting, Inc. for letting me steal his content and images. 🙂

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4 thoughts on “basic container design – structural considerations

  1. I like the container shack out in the woods. How many Code violations can you count? I noticed three – the chimney terminates below the roof line, there is no landing at the top of the stairs, and there are no windows in the containers, which are required for egress from sleeping rooms. To funny.

  2. Pingback: A Good Question Considering Shipping Container Structures | Runkle Consulting Inc.

  3. In the example where the sides are removed and the structure failed under standard loads, was the tubular steel removed, or just the siding? If the tubular steel was removed, I wonder how much better it would have resisted the loads if the model was run assuming only the siding was cut out??

    • My understanding is just the siding was removed. The essential nature of a container is that it acts as a single structural unit. If you remove any portion of the unit it becomes structurally unstable even under normal loading. This is why special reinforcing design is required for container structures beyond what a layman would be capable of.

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