Robyn Volker and Anke Irmscher decided to paint their shipping-container home bright orange because, as Ms. Volker said, “you might as well announce it’s a container.” credits: N.Y.Times
Shipping container homes have grown immensely in popularity in recent years for several good reasons: they are durable, eco-friendly, and modular. More importantly, approached correctly, they can be built both faster and more affordably than conventional homes. The first two-story shipping container home in the U.S. is said to have been designed by a California architect in 2006. Since then, the rate of shipping container housing has steadily accelerated in response to the increased cost of home construction. Here are some tips for those considering a shipping container home.
Understand the Modular Nature of the System: Modularity is what lends the potential for affordability and speed of erection to shipping container construction. But these advantages can become pitfalls to the unwary. Shipping containers are neither very tall nor very wide – usually 8 ft wide by 8.5 ft tall – dimensions that can make for awkward living spaces. Several containers need to be assembled together, smartly combined, and openings cut between them in order to make comfortable living spaces while still maintaining affordability.
Evaluate Zoning Ordinances within your Jurisdiction: One of the first steps towards your shipping container home will be to establish its feasibility from a zoning standpoint. Just like any other building, one built from shipping containers will need to conform to zoning ordinances regulating things such a maximum allowable size, height, and setbacks. Additional overlays may apply if your site is, for example, within the Coastal Zone, falls within a riparian setback, has protected flora or fauna, etc., etc. Whether you are considering your project as a new home, an addition to an existing home, or as a second unit (ADU) are all zoning-related considerations. You will want to meet with your local planner, or delegate this to your architect, in order to evaluate this aspect of your project.
Understand Building Codes Impacting Your Project: A shipping container is an extraordinarily robust structure, meant to withstand extreme-loading conditions at sea. Adapting it for use as a home, which naturally entails cutting openings into it for doors and windows, compromises the structural integrity of the container. The building codes will require structural evaluation to determine, and if necessary mitigate, such that the inherent stability of the container is not compromised. If your proposed project is greater than 500 square feet, the Codes will in all likelihood trigger that you obtain a geotechnical investigation determining the capacity of the soil to support the building’s foundation system. This in turn may inform the design of the foundation system necessary to support your proposed building.
Consider Your Design Options: Among your design decisions will be to determine whether your shipping container home should be one-story or two-story. For your next decision fork, you will need to decide whether to “marry” your shipping containers into create a single building, or deploy them separated from one another with the spaces between them in-filled with conventional construction (a so-called hybrid container home).
As with any conventional home, given the increased costs associated with a two-story solution, the option to go upward vs. outward is usually predicated upon the limitations of lot area rather than cost effectiveness.
In terms of a one-story solution, “marrying” your containers together into a single structure carries with it advantages including simplification of assembly, rapidity of construction, and elimination of unnecessary trades. Conversely, deploying your containers apart from one another and infilling between them, while likely to be more costly, will result in greater flexibility.
Caveat Emptor – Look Before you Buy: You would never purchase a used car without first looking under the hood. When purchasing a used shipping container, you will most likely not be able to do a complete “walk through”, especially if it is currently located at some obscure port. However, you can ask the seller for detailed pictures and a thorough description of the container. Older shipping containers might have several dents, issues with rust, or other structural problems that come with a lifetime of being tossed around on the high seas. One-trip containers are a little bit more expensive, though they are almost assured to be in great shape, and may be worth the investment. In any event you want to avoid the work and expense of repairing a container that is so dented up or rusted as to compromise its structural integrity for building purposes.
It is also recommended to buy all your containers from the same manufacturer-of-origin. Containers from different manufacturers may have small differences in structural characteristics and dimensions, and combining them may diminish the ease of using containers to build your shipping container home. Thus it is in your interests to locate your best single source working locally, and purchase from them only a uniform product.
Factor Your Preparation of the Container into Your Budget: The wooden floors used in the majority of shipping containers are treated with hazardous chemicals including preservatives and pesticides. Metal surfaces of some are coated with paint containing potentially harmful chemicals such as phosphorous and chromate. Preparation to mitigate these concerns would include demolition to remove the floor system, and either sandblasting or encapsulation to deal with the existing paint.
Foundation System Considerations: One of the virtues of container construction is that the module has tremendous capacity to span from point to point along its underside. Assuming the long walls are not seriously compromised by cutting-in new openings, the system lends itself to an isolated pier foundation system. This offers real savings both in labor and materials costs relative to a conventional spread footing systems as compared to those necessary to a conventional wood-frame home.
Minimize Cutting: Every cut you make into a container’s roof, wall, or floor requires time and money, and complicates the construction. Whether you sort out your own design or work with an architect to come up with the most efficient solution, your goal should be to work within design parameters requiring the minimal number of cuts.
Minimize Welding: Whether you are combining many containers to result in a single structure, or only 4-5 containers by “marrying” them together, how they meet each another is a design consideration having budget impacts. This is true both in the vertical as well as the horizontal plane. Field welding is not only expensive in itself but, under California Building Code, must be observed by an outside inspector, thus accruing additional costs.
Make Sure You Have a Plan for Insulation: An unfinished shipping container will be hot in summer and cold in winter. Moreover, the building codes will require that you address this item. When designing your shipping container home, remember that you will have to insulate the roof, walls, and beneath the floor. Insulation applied to the interior of the container will be cheaper but will eat up precious interior volume; insulation applied to the exterior will optimize interior volumes but will incur the additional costs of cladding (covering) the insulation in order to keep it dry and protected. It is thus in your interests to investigate the options which best serve both your long-term comfort as well as your budget.
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