Engineering Modified Containers

As the modified container market is relatively young, it’s hard to find much information available on best practices and conventions.  The internet is a fountain of misinformation on this topic.  Here are some tips to get started.

Container 101

First of all, we have trained plenty of engineers and architects on designing with containers and have presentations available.  Email us and we are happy to send one to you.  These have all the parts of the container labeled with their correct names and illustrate how they are connected in shipping.

Obtaining a Drawing

The biggest problem engineers have is that containers are all constructed a little bit different based on the manufacturer and their customer.  The ISO spec dictates performance but does not specify how it is achieved.  For example, some people build containers with tube steel for the top rail.  Others use flat bar.   Another problem is the corrugation patterns are different.  If you design something to be attached to a hump 6” from the post and the clients buy a container where 6” is a valley, obviously that won’t work.  We can recommend a top level wholesalers of new containers.  They can send you the engineered drawings used for production.  The caveat is that if your clients end up buying them somewhere else or trying to save a few bucks buying used, all your drawings will be wrong and won’t work.

Building Codes & Toxicology

Over the past couple years the boards of the two industry associations, the MBI and the NPSA, have worked together on having shipping containers added to the IBC.  For this effort, they had an independent third party prepare toxicology testing reports.  They also had the foremost container engineer publish known quantities for loads and other factors.  The summaries of these and other findings can be found here:

https://www.npsa.org/Modified-Containers

Fire Rating Certificate

A few years ago there was also a study done on the fire rating of a container.  We can email you copies of this report.

New vs Used for Building

You’ll hear varying opinions on this, but we always recommend using one trip containers, and high cubes for dwellings.  Additionally, after finishing out a ceiling, the extra height in a high cube will usually be needed for code.

Used containers have been traveling the ocean full of cargo for years.  There’s almost no record to keep track of what was shipped inside them.  Anyone who has this information will consider it proprietary.  Aesthetically, they are rusted and dented and even after they are painted they don’t look great.

Additionally, the dents affect the structural integrity of the system in unquantifiable ways.  A used 40’ high cube is about $2000.  A new one is about $4000.  The customer will spend more on labor trying to get a used container to do what the drawings say than if they had just bought new.  We’ve seen welders cut into them and the container goes “boing!” and twists into an unusable mess.

Value Engineering Tips

If clients are concerned about cost, the most cost effective way to design a structure is to configure the containers in the way they were designed to be used, which is with all the load transferred on the corner castings.  Cantilevered and perpendicular designs all have to be reinforced with structural steel.

Roof penetrations such as skylights also cause problems, making them more expensive.  The roof of a container isn’t flat.  It’s slightly convex to aid in water runoff on the ocean.  Modifications can be done but it is not easy and will likely have to be maintained by the client with caulk.

Be sure your clients know that building container structures is not cheap.  It’s equal to or more expensive than traditional custom building.  The way we explain it is that all the materials that go into it are exactly the same as those in a traditional building.  The only difference is the frame is steel instead of wood.  Which is more expensive, steel or wood?  You save some money by using factory labor instead of onsite labor.  The reason to do a container building instead of traditional construction is that it is much much faster and you wind up with a sturdier product at the end.  They should plan on $175/Sf at a minimum, not including land, delivery or setup and that number can go as high as $350/Sf if they want cladding and containers hanging off each other.

Who Can Build It

If your clients don’t have a contractor or factory in mind yet, we are happy to recommend a few reputable ones across the country.  As the industry is so new, there are a lot of people who think working with containers is easy and start companies.  They quickly find out they were underestimating how hard it is.  I’ve heard from too many clients with shoddy work.

More questions?  Contact us

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