There is a LOT of talk all over the blog-o-sphere and news lately about container construction. Projects are being developed here in Jacksonville for low income/homeless housing; in Haiti for relief housing and medical shelters; there are even projects in development that propose multifamily housing complexes made entirely of shipping containers from California to NYC and from Texas to Michigan. Something that I’ve noticed lacking in the mainstream is a little education on “how to” with shipping containers. There are sites out there, don’t get me wrong (I even have a couple of them on my side bar), but compared to the sites simply displaying pretty pictures (I love pretty pictures as much as the next guy, or what I call “archi-porn”), but really we need a little something more. In order to remedy this, I’m going to do some posts (hopefully one per week if I can remember) on various construction techniques for working with shipping containers. I’ll start with the various components of the building envelope and work our way around.
sketch of container wall section - copywrite 2011 r | one studio arch
First, I want to talk about how to properly insulate and construct a finished wall, interior/exterior, using shipping containers as the base structure. Before we get into that we need to understand some basic information about shipping containers. One – they are metal. They are covered in toxic, nearly indestructible paint and floored with OSB/Plywood soaked in formaldehyde….NOT exactly a recipe for clean, safe housing. Two – being made of metal, if we leave them exposed, will transfer heat from the outside to the inside. Three – not all shipping containers are created equal. Buying containers from various manufacturers in order to save cost will only give you headaches later when you realize that the size is off just a SMALL bit. This creates headaches when trying to stack or otherwise join the containers.
Ok, with those basic points out of the way, lets get back to our wall. We’re talking about optimal wall construction here. First thing we need to do is sandblast the container to remove the nasty paint that covers the surface (check with local authorities on how to properly dispose of toxic paints and other materials). Once we’ve done this we need to encapsulate the container in a rust-proof paint – either polyurethane or enamel. This ensures that the shell will remain intact….pretty much forever.
Now our container is relatively safe from the elements and we are safe from our container. It’s time to start attaching our substrate to the outside of the container (we’ll worry about the inside in a minute). We’ll be using 2×3 pressure treated wood furring and angle iron to create basically a framed wall on our container. The angle iron we weld to the top and bottom rails of the container to create channels that the furring will fit into. Then we take our 2×3 P.T. (pressure treated) wood furring and attach it to the container vertically about every 12-16 inches. To attach the furring we use commercial grade construction adhesive (liquid nails for short) and screws. Check local building codes or talk to your local officials about code compliance for this step. Once dry we can proceed with the most important part of our wall – spray foam insulation. There are two types – closed cell and open cell foam. Closed cell does not allow the passage of air or moisture. This is what we want. Also insects and vermin won’t touch it. By applying 2 1/2″ of foam (the depth of the furring) you get an R-value of about 6.0 per inch (in case you don’t have a calculator handy that’s about R-15 for 2 1/2″ of depth). Now that we’ve protected, insulated and furred our container we can apply finish. This can be any common exterior finish – stucco, horizontal siding, vertical siding, t-111, whatever. Be sure to follow recommended manufacturers recommendations on proper attachment.
The interior is a different animal. We’re limited by our width, depth and height in a container, so we have to make careful use of the available space.The first and most important choice we need to make that will determine how we proceed with interior finishes is whether we want recessed or exposed electrical devices/receptacles. If recessed, then you need to use at least a 2×3 interior stud with 1/2″ gypsum board (3″ total thickness and 6″ lost in each direction). If exposed conduit and receptacles than you can get away with using 1x furring and 1/2″ gypsum board (1.25″ depth and only 2 1/2″ lost in each direction). Using the 2×3 studs has an additional benefit – it allows you to add rigid or batt insulation in the stud cavity. This is especially nice if you are building in northern climates where the winters are more harsh than the more temperate Florida that I live in. If the loss of additional depth is not to your liking, you could also simply use larger studs on the exterior and pray a few extra inches of foam to up your R-value to say 33. This combined with some carefully designed openings can significantly reduce your hvac requirements.
Once you’ve installed your interior gypsum board you’re ready to tape, mud and paint. You’ve got a wall that is water tight, air tight, insulated against heat transfer and is all but impervious to insects (have you ever tried to eat foam?….yeah, there’s a reason for that). Next week we’ll talk about how to reinforce, insulate and install a floor in a container home – both with slab on grade foundation as well as a raised stem wall.
Anyone with direct experience or past construction projects to highlight as examples, please send me an email or comment here. Maybe we can even have a guest post or two. 🙂
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This is what I was looking for. I’m aware of Tyvek vapor barriers being used for regular stick houses, but wasn’t sure if I needed to use it for a container house. From what I read, the answer is no. This article confirms what I’ve read in other articles about the closed cell spray foam insulation being impenetrable to water and acting as it’s own ‘vapor barrier’ and insulation.
-Are we sandblasting both the interior AND exterior? Applying the same rust-proof paint to both surfaces also? And recommendations for paint?
-Because I plan on building mine in Upstate NY, winters are cold and summers are fairly hot. I was throwing around the idea of studding out the interior with 2×6 walls. I wonder if I could get away with 2×4 walls? Any recommendations?
I would fur out the exterior not the interior. A 7′-6″ wide space that is then furred out with 2x4s suddenly becomes very VERY small. Also, spray foam in not impenetrable to moisture. Even closed cell will allow some moisture and air to pass through. What you need to do is study the dew point of your location and design your walls accordingly. There is no silver bullet here. Weatherproofing is site and building specific.
Best of luck.
What I failed to mention is that I plan on slapping two 53′ high cubes together, side by side. That is IF I can get my hands on them. Otherwise, it will be 45′ high cubes. So, I will have 16′ of width to work with, rather than 8. But I hear what you’re saying, studding the exterior would make the interior much more roomy. My other concern with studding the exterior would be finishing the outside with something…another added expense that would most certainly be more expensive than drywall on the inside, per square foot. I’d like to sandblast the outside, slap a couple coats of super tough paint on and call it done.
If you’re going for the Mad Max Cabin look, sure. Expense is relative to what you use. Some metal channels, the right liquid applied air/vapor barrier and some vertical wood siding and stain/sealer and you’re done.
Drywall is more complicated than you think. Especially if you want it to look good. Also, if you spray the interior you need to think more carefully about your electrical, as these boxes will need to be fixed beforehand. If you want to change it later you’re interrupting your insulated envelope. Much better to insulate exterior.
Last thing to think about – you have an exposed metal box. I’m from New York. Summers are hot and there is a lot of sunshine. That exposed metal box WILL radiate through your insulation.
You know what, I just thought about a board and batten siding…made from rough cut hemlock would look rustic and wouldn’t break the bank. I’ll think about it. I’m not sure what you’re talking about when you reference ‘spray the interior’. But, if you stud out the interior, running electrical lines, adding outlet boxes, switches, can lights etc. would be just like a stick house…unless I’m totally missing something. I was thinking of coating the exterior of the box with superthem. I just got a quote from a company in New Jersey for 45′ high cubes for around $4000, delivered. The break down was $2500 for the container, $1500 for delivery. I googled shipping containers for sale and New Jersey, because of it’s port status, and found some companies that got right back to me. I got responses from portcontainersusa.com and iport.com. Still holding out on the 53′ high cubes though 🙂 There are a couple on eBay right now in Seattle for $5700, not including shipping. For less than half, I think I’ll make do with 45 footers.
That’s a hell of a deal. They must really be hurting if they’re letting them go at that price.
Good luck. If you ever need design/detailing help let me know. I’d be happy to provide services.
And if you have a connection for high cube containers I’d love to hear it. I’ve never been able to purchase them. Standard size only – 20′ and 40′. Some 53′, but never a 45′. They tend to stay in use for as long as humanly possible due to their size.
Good morning,
I have a question concerning the ceiling of a shipping container. If you merge two 20f shipping containers together and remove the walls in-between I’m assuming you need to add strength to that seam in the wall. Would it be a load bearing beam?
Yes of course. Shipping containers are a single structural unit. As soon as you cut into the envelope you remove it’s structural integrity.