What’s wrong with shipping container housing? Everything.

What’s wrong with shipping container buildings? Nothing, if they’re used for the right purpose. For a temporary facility, where an owner desires the shipping container aesthetic, they can be a good fit (look, I’ve even done a container project!). For sites where on-site construction is not feasible or desirable, fitting a container out in the factory can be a sensible option, even though you’ll still have to do things like pour foundations on site. It probably won’t save you any money over conventional construction (and very well might cost more), but it can solve some other problems.

The place where containers really don’t make any sense is housing. I know you’ve seen all the proposals, often done with an humanitarian angle (building slum housing, housing for refugees etc) that promise a factory-built “solution” to the housing “problem” but often positioned as a luxury product as well.

This post on ArchDaily got me started on a Twitter rant about the unsuitability of containers for these projects, and the larger trend of online design publications not bothering to ask any questions and run these press releases as “news”. Not to mention the architects themselves presenting this idea as a feasible solution to a major problem.

This is the project that got me started, a recent competition winner by GA Designs, which proposes it as a solution to slum housing conditions in India. There are a number of glaring problems with this idea (some of which Llyod Alter takes on in a post on Treehugger) :

This is a particularly colorful version from OVA Studio (this is for a hotel):

Another slum housing “solution” reported in Dezeen:

A short list of why shipping containers are not a “solution” for mass housing:

1. Housing is usually not a technology problem. All parts of the world have vernacular housing, and it usually works quite well for the local climate. There are certainly places with material shortages, or situations where factory built housing might be appropriate- especially when an area is recovering from a disaster. In this case prefab buildings would make sense- but doing them in containers does not.

2. If you are going through the trouble of building in factory, why not build to a dimension that is appropriate for human habitation? With only 7’ clear (2.1 m) inside a built-out container, you are left with the building code minimum room width as your typical condition. It’s hardly an ideal width, and it is not difficult to ship wider modular units: modular home builders do it all the time.

3. Insulation. All surfaces of the container need to be insulated, and this means either building a new set of walls on the inside or outside of the container. If walls are furred out on the interior, this is convenient for plumbing and electrical lines but it narrows the usable space of an already small box. It also allows for a huge amount of thermal bridging unless the floor is built up with insulation on the inside (which brings up a host of other problems).  If the exterior is insulated it no longer looks like a container, and then you have to pay to clad the entire thing over the insulation. In either scenario you’re duplicating all of the walls that you started with. Improper insulation will result in heavy condensation on the inside of the metal exterior walls.

4. Structure. You’ve seen the proposals with cantilevers everywhere. Containers stacked like Lego building blocks, or with one layer perpendicular to the next. Architects love stuff like this, just like they throw around usually misleading/meaningless phrases like “kit of parts.” Guess what- the second you don’t stack the containers on their corners, the structure that is built into the containers needs to be duplicated with heavy steel reinforcing. The rails at the top and the roof of the container are not structural at all (the roof of a container is light gauge steel, and will dent easily if you step on it). If you cut openings in the container walls, the entire structure starts to deflect and needs to be reinforced because the corrugated sides act like the flange of beam and once big pieces are removed, the beam stops working. All of this steel reinforcing is very expensive, and it’s the only way you can build a “double-wide.”

5. Stacking. One recent competition boasted that because containers can be stacked 9-high, concrete floors could be provided every 9th floor with stacks of containers in between. That load still needs to travel down through the building, and still then requires columns. Those floors every ninth floor need to hold the entire weight of 9-stories of building above, which makes it dubious that you’d really be saving much on structure. The foundation also needs to be built similarly to a “regular” site-built building, and this is one of the most expensive pieces. Stacking also requires a large crane and an area for staging the prefabricated container modules, which can be hard to arrange on a dense urban infill site.

6. Utilities and Mechanical Systems. In a large building, you’ll still need a lot of space to run utilities. Because of the problems with insulation mentioned above, you will need to install a very robust HVAC system to heat and cool the building (that Mumbai tower shown above would literally be a deathtrap without cooling). You will have a hard time taking advantage of passive strategies like thermal mass if you maintain the container aesthetic. You’ll also end up with low ceilings, as even high cube containers are only 9-’6” (2.9 m) in overall exterior height, so any ductwork or utilities start cutting in to headroom.

7. Recycling. Part of the container narrative is that it’s “green” because we have a surplus of containers that can be reused. This is somewhat true, but in reality many existing container projects use brand new containers from China (which are still very cheap to buy). Used containers need to be thoroughly cleaned because there is a risk they may have been used to transport something toxic in the past.

What you get with a container is cheap structure, if you can use the box-basically as-is. As soon as you remove anything (including the ends) you need to hire welders and buy steel. Architecture is more than structure though and structure on its own is not particularly expensive- especially when you are building a space as small as a shipping container, so the savings here are minimal. Relatively untrained people can build a room that size of simple wood framing in a day without needing to rent a crane or learning how to weld for about the same cost (or less) than buying a used container.