Image Credit: Mark Hogan
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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 a 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.
Competition winner GA Designs had proposed the shipping container skyscraper 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).
A short list of why this won’t work
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 feet clear 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 nine 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 nine 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 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-foot-6 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.
Mark Hogan is an architect and the principal of OpenScope Studio in San Francisco. This post originally appeared at his website Markasaurus.
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13 Comments
Mark
Nailed it - although you were perhaps a bit too kind.
They excel at what they were designed for: transport and unheated storage.
Housing fads
Over the years, housing fads come and go. Domes came and went. Now it looks like the shipping container idea is finally fading away.
What amazes me is that these ideas, which can be determined to be foolish with only 4 minutes of thought, get as much traction as they do...
Martin
It's a bit like real estate bubbles or other fads and fashions. Before they fade or crash, a few boosters often manage to make a lot of money. Your inherent rationality has probably precluded you from investing in any number of nutty schemes that could have left you lounging in an energy-hogging Mcmansion by now.
Container Homes issues are the same as all home issues...
While all of these issues are sort of true, I would just like to point out that with proper design all of these become moot points, just like they do in more traditional wood or concrete construction.
1. A client wants to build a custom home using containers. What does this have to do factories or disaster housing? Moot unless this is a conversation about disaster housing.
2. Factory limited to 7' wide... this is moot unless you find a factory container builder. I would also point out that modular builders do build homes wider than 7', so I am not sure where that limitation comes from.
3. Insulation and thermal bridging are an issue with all types of construction (looking at you, metal clad window manufactures!) and always pose condensation concerns. However, it is nothing that cant be mitigated with proper building materials and some thought. You know how the steel pan-deck on the bottom of your garage slab has a little bit of foam on there to prevent condensation? Or your basement wall? Yeah. You want that on your container too. This issue applies to all types of construction, not just containers.
4. I am a little bias here... but working with a structural engineer sort of fixes the issues of structure. However, it does not fix the issue of poor floor plans and poor designs that don't account for mega-huge and expensive beams needed for that 30' wide open floor plan kitchen/living room... but again... that applies to all homes not just containers. Just like engineered roof trusses can get you more open great room spans than an engineered beam and traditional rafters.... proper design makes this issue moot. I agree that cutting containers OR wood willy-nilly without an idea of how structure works is dangerous and not recommended.
5. Stacking... 9 stories tall... I don't care if you make a 9 story tall building out of containers or unobtanium there are going to be some serious structural considerations. I agree that containers may or may not save you money with large commercial or with small residential construction, but again the design is going to dictate that just like it does with all types of construction. This is moot unless you have a cost comparison of containers vs traditional structure cost for a high-rise building, which still would not actually apply to most homes.
6. I tried to google search 'Mumbai tower', but it appears Mumbai is a city with 3000 high rise buildings. The utilities and mechanical chase issue applied to all of those buildings too. I don't see how a container made of wood and steel is any different than a steel and concrete commercial building or a wood residential building. We recommend mini-splits in most of our smaller units which fit within the framed walls or above the closet. This would also work for your container-hotel. While india has some robust air-conditioning needs those of us in climate zone 5 and above have some heavy duty heating needs. A wood stove and/or a variable speed heat pump fit in a container, or a geodesic dome, or a yurt.
7. I agree that the 'green-ness' is questionable. That steel could have been recycled into some other helpful steel item, but now you are essentially using it as exterior cladding. I feel the same way about concrete, but people build houses out of that too.
The biggest problem with container homes we see is that people read all these little articles, written by people who have never built a thing in their life, and then call us thinking they are sooooo much cheaper than typical construction. Hint: Container homes have the same code requirements as a stick frame home for plumbing, insulation, water proofing, electrical, fire proofing etc etc. and with the additional trades required of welding, cranes, plus hiring a structural engineer. Not only do you need a set of plans from and architect or an engineer noting the structural connections $$$ sometimes the inspections departments even want us to inspect the welding $$. And for good reason, nobody wants a home to collapse or blow away because they didn't nail, screw, bolt, or weld things together properly.
At the end of the day your custom container home is going to cost about as much, but likely slightly more, than a wood-framed home, and also have a few more issues to think about (how exactly do we bolt these roof trusses to a metal container without screws being visible inside?). "But it looks so cool and modern!" they say~ well, metal cladding looks cool too and avoids a lot of these issues. Heck, you can even put a green roof on a wood framed house if you really wanted.
I am really itching to do more passive solar earth-bermed hobbit houses and geodesic domes. I hope those come back into style soon. They are much more fun than metal boxes, though the aesthetic tends to be more middle-earthy than modern. At the end of the day we end up designing whatever it is the client wants, whilst trying to steer them in a more reasonable direction. 7,000 square foot timber frame homes with 20' tall picture windows in the living room, in a 120mph wind zone, and 30' retaining walls for the yard pose their own set of structural and energy issues that are much harder to overcome than anything on this list... but they want what they want!
I do want to note my bias and experience; I work for a structural engineer that has done 10 or so container home projects. It seems about one or two lucky people a year actually go through with it, but the vast majority use more typical, and perhaps more reasonable, building components.
In 30 years will we look back and wonder why we ever let people build with wood? Maybe. Currently about half my job involves repairing rotten wood structures, so future me hopes we keep doing it for job security, but sustainability minded me really wants us to think a little harder about how we flash and water proof our wooden homes.
I just realized I ranted longer than the article. Sorry!
-Quint
Response to Quint David
Quint,
You used a lot of words to say that it's possible to surmount all of the problems that come from using a steel container -- but you'll end up with a home that is more expensive than one built with conventional materials.
OK. I agree.
Expense
The question on everyone's mind would be 'well, how much more expensive?" or "compared to which conventional material"?
The correct answer on expense would be 'it depends' (hey we are engineers, not contractors!). If you want to take a broad stroke you could say 'usually, but not always'.
The same goes for most all alternative methods (strawbale, double stud walls, icf, anything designed by an architect) that a contractor is not used to or not interested in working with. I still cringe every time I see a nana wall on a set of plans and the client has no idea of the cost yet. The exterior walls may be less than 20% of the cost of the structure, so even if you built them all out of free dirt (even cheaper than cheap dirt!) many of the other components would still cost the same. Free dirt might even cost more than wood if you hire the wrong people.
Many clients don't want to use the cheapest building materials possible. They want to use the ones that are going to provide them a long-term investment in their own enjoyment. For energy nerds like us that may mean a windowless box surrounded by foam with pv panels on top, but for other folks they sometimes don't mind spending a little extra energy for a little more enjoyment, or natural light.
We always try to steer them towards that light, but when they are really set on a log cabin milled from trees on their own property... well... if it makes them happy that is what is important. Some people like the same cookie cutter house as their neighbor, but slightly better of course, and others don't like to see any neighbors at all.
I am glad this site lists wood frame, SIPS, ICF, timber frame, and 'natural materials as exterior wall options, but for readers less familiar with the cost of these 'conventional materials' an article about the costs of each would be a very interesting and helpful read for some of our alternative clients and may help steer them to a choice that makes them happy without us having to explain it all the time.
-Q
Response to Quint David
Quint,
You wrote, "I am glad this site lists wood frame, SIPS, ICF, timber frame, and 'natural' materials as exterior wall options, but for readers less familiar with the cost of these 'conventional materials' an article about the costs of each would be a very interesting and helpful read for some of our alternative clients."
I agree, that would be a useful article -- just one that is tough to write.
How much does a straw bale wall cost? The range is huge. But, as a journalist, I know that it's possible to tackle the topic.
I took a stab at the topic in my article, "How to Design a Wall." In that article, I wrote, "In most of the U.S. and Canada, there are two cost-effective ways to build a wall with an R-value that exceeds minimum code requirements. The first approach is to build a double-stud wall. The second approach is to build a 2x6 wall with a continuous layer of insulation (usually rigid foam or mineral wool) on the exterior side of the wall sheathing. ... Other types of wall assemblies, including walls using ICFs, SIPs, Larsen trusses, straw bales, or adobe, can be made to work, and in some cases have a few advantages for certain locations or applications. But these approaches tend to cost more than a double-stud wall or a 2x6 wall with insulation on the exterior side of the wall sheathing."
heres the facts. TONS of people around the globe are ALREADY using shipping containers for homes. Im watching tons more in the process of building them. Ive yet to run across many who ARE living them now tossing fits of rage over not being happy with them.
So I use a stick build for a little less and end up with a structural problem due to insects or other wood boring pests.
Or...I build using a steel container, pay a little more and get a structure that is FAR more durable.
I'll take door number 2, chuck.
Can you please define "TONS"? I've never seen a single one.
A Ton is 12000 people
I know a guy in NL named Ton (who does NOT live in a cargo can)- just one person per Ton, not 12,000 people.
Maybe it's a metric-to-english units conversion issue?
Tons of people in the world are living in wattle & daub huts without "... tossing fits of rage over not being happy with them..." too.
That doesn't mean it's an optimal solution that others should adopt.
Those who choose to live in shipping container houses tend to be enamored of the idea, and somewhat immune to any of the deficiencies.
>" Im watching tons more in the process of building them."
Really "...watching tons..."???
Are you in the business of building them?
Is this a hobby or something?
Are you doing site surveys or field studies of their relative cost & energy use performance?
I've only advised one person who actually followed through on building one (or rather, having it built for her) who actually intended to live in it year-round in a cold climate (if Whitehorse Yukon is considered cold). For most it's a bit like the Tiny House thing- trendy - kewl for some, but not for the average person. Lots of online videos of people sharing their Tiny House features & experiences, with some who actually live in them year-round as a means of coping in a high real-estate cost environment.
I have a relative who uses cargo cans as secure storage sheds (complete with pretty good interior lighting) on his property, something they are far better suited for than as a residential habitat.
Re-read this section:
4. Structure
Unless you are a structural engineer and a certified welder, you are putting a minimum of $30k line item to your build cost.
There are a lot of better ways I can think of spending that money when it comes to building a house.
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