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.
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. 🙂