DIY Container Housing

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Eric Hunting:

"Container housing has been very popular of late and works well. It's a very well proven means to very durable low-cost housing, but costs vary greatly with design approach and location. There are few-thousand-dollar container homes and million-dollar ones too. There are also many prefab offerings now that some consider modest in cost. For the owner-builder, the potential approaches will depend on an assessment of your skills, particularly in metalworking. For a long time the cost of container housing has been inflated in the US, compared to other countries where it's used, because the metalworking labor was scarce and expensive and most 'container modding' was done by companies producing mobile offices/housing/workshops for industry and the military--and where a large 'executive premium' was added to the prices of things. This changed somewhat as public awareness of the existence of shipping containers increased and markets emerged for their uses as farm and back-yard storage sheds.

There are several basic container types; conventional 8x20' and 8x40 in 8' high and 'high-cube' 9' high forms. These are found in 'dry shipping' form with the usual corrugated steel walls and insulated form that use a thick structural insulated panel with a stainless steel sheet interior and aluminum deck planks for flooring. The latter is rarer on the used container market but generally easier to work with for the DIY builder. 40' containers usually have doors on both ends and support posts in the middle of the sides. 20' usually just have doors on one end, though different door arrangements aren't unusual. Insulated containers may have a recess and portal on one end to accommodate a modular refrigeration unit, which can sometimes serve as a utilities enclosure. Containers are usually made with welded-sealed roof panels using the hollow corner posts of the containers as run-off channels. With houses, this may also use internal PVC pipes or channels.

Recently, some new offerings have appeared presenting new design options and building approaches. Companies renting and selling these as storage units have started offering odd-sized units beyond the standard 8x20 and 8x40 sizes. You can now get 10x18, 10x20, and 10x25 'extra wide' containers designed to allow two parallel rows of shipping pallets to be placed in them with a walkway through the middle.

The Chinese have gotten into container housing in a big way, Recognizing there's a large global market for them, many companies now offer very low cost bare container frames designed for prefab housing use, as well as more complete house kits based on cheap alloy structural insulated panel. These are 'knock-down' frames in that they fold flat as stackable units, allowing several to be stacked in the space of a standard container for convenient shipping and transport. It's always hard to get solid pricing on these international trade sites, but these frames seem to be selling for between $500-$1000 per 20' unit and twice that for 40'. These frames offer the most flexibility in that they are designed to accommodate any kind of exterior/interior wall cladding, though usually intended to use various kinds of structural insulated panels. These are more economical for designs that are planning to put a set of containers together to make a relatively large structure, as stripping-down conventional used containers for that purpose can become expensive. They are also good where you want to conceal the use of the container frame, particularly with the use of additional exterior cladding.

These listings offer some representative pictures. The text info should be taken with a grain of salt.

There are generally three approaches to outfitting containers depending on what the source containers are. Conventional dry shipping containers will be 'framed up' on the inside walls and ceiling to accommodate conventional wall paneling, insulation, and low-profile electrical and plumbing fittings. This is done either with light steel framing spot-welded to the existing steel walls or using wood framing with sill beams and posts attached to bolts welded to the frame and/or walls. Insulated containers have welded structural insulated panel walls and ceilings and can be used as-is with utilities surface-mounted or can mount wall coverings directly with screws or using wood strips. Fully stripped container frames will employ conventional SIP panels adapted to size or be framed up securing posts to the top and bottom of the frame. If not using something with a pre-finished exterior surface, additional wall cladding may be needed.

When joined together in series at their corner blocks, there is usually small gap between the corner posts of the container frame and many approaches are employed to close or seal this. For permanent housing the most common approach is to weld plate covers onto to this to make a permanent seal. More demountable approaches use gaskets, injected polyfoam, industrial tapes, and usually some kind of thin alloy cover. For a large series it's also common to employ a new composite membrane roof or a retrofit roofing system. Heat gain is a big issue even with insulated containers and many people feel a need for the traditional pitched roof, so adding roofing on top of containers is common. Insulating/reflective paints like Thermoshield (originally developed for insulating rocket hulls) also help with heat gain issues.

The simplest container homes need little more than a gravel bed or precast concrete corner pads for a foundation but the most common types of permanent foundations are concrete pier systems which let the containers plug into deck pin mounts on the top of the piers. Where the ground is pretty level, prefabricated pin-pier foundations offer a good low cost foundation system. They're pretty good for any type of Tiny House application.

Recently, screw pilings have started being used with containers and, though they require special installation equipment, they offer the ability to accommodate varied terrain as with conventional piers with much of the reduced labor, reduced environmental impact, and simplicity of pin piers. But these lighter forms are usually limited to single-storey structures.

Container homes can get very elaborate, and thus very expensive, especially in the hands of architects. The most economical way to work with them is to accept them as they are and make the most of the end-openings they already have instead of trying to add windows, doors and what-not to the sides, which demands more elaborate metalworking. Put a commercial sliding glass door frame into the open end of a container and you're pretty-much done. But the 8' width of the conventional container is confining for many people. A two-container unit is the most convenient, multifunctional, room size. Indeed, if there was such a thing as a 16'-20' square container unit, it would be the ideal housing module. (and the Chinese could probably easily make that, but then wouldn't know how to ship it…)

The simplest and most flexible way to make a container home is to make a 'compound' home. A compound home uses small free-standing structures as individual rooms and links them by walkways or clusters them around a common deck. But since you have to go outside to move between them you are relying on landscape for privacy and need a location with a climate mild enough that this isn't a hassle. This approach also has the benefit of skirting around permitting and building codes as no individual structure is big enough to be considered a 'real' house. By itself, the typical 20' container is a useful individual room size for this application and a dual-container module not terribly more complicated.

One of the nicest container mods I've seen is also one of the simplest; a 'surf shack' designed by Hartman Kable in Seattle. (Seattle is something of a hot-bed of 'cargotecture' and home to one of the best architecture firms working with them; Hybrid Seattle)

This really demonstrates how nicely appointed a container can be with absolutely no physical modification to its original structure. Now this interior is a bit elaborate because the designer was trying to pack so much different functionality into one tiny package. It's very 'gadgetized', which makes for some rather labor-intensive interior finishing. In a compound house a unit like this would be more specialized in function and so its interior design would be much less cluttered.

When modding containers it's much easier and cheaper to strip out an entire wall or a large floor-to-ceiling section then to frame individual doors and windows--though that is easier to do with the insulated containers where you can get away with the kind of clamping frame prefab windows and doors used in RVs and boats. (the same kind you see used with the SIP paneling on those Chinese container houses) It also gives you a big piece of wall material to repurpose for things like a fold-up deck shade or fold-down deck area. In some designs the perception of narrowness in single container is overcome by opening one side to make a large window-wall, often with sliding doors and a deck area.

Another approach suited to compounds is to use containers placed in parallel to support shade canopies between them that provide partial enclosure. There are some companies that now prefab such canopies for use as garages or container shops.

I'm personally very partial to Modernist pavilion architecture as open-plan design more easily accommodates the use of low-toxic materials and interior design based on 'furnitecture'; furniture that blends elements of architecture and furniture to define more volumetric uses of space, such as Ken isaacs' Living Structures. Most pavilion homes are architect designed bespoke steel and concrete constructions that, of course, tend to be ridiculously expensive. But there are a number of prefab structures suited to this offering much greater economy. For instance, prefab park pavilions. But even those are a little on the high-end. So I've considered the use of bare container frames for this, which thanks to the Chinese is now very affordable indeed. Basically, one would combine a series of linked bare container frames as 20' or 40' structural bay units and top them with any of a number of simple roofing systems, such as the Epic Metals pre-finished roof deck system.

One could employ simple self-supporting arch roofs or flat roofs with this. One then need only finish the floor (including utilities and radiant heating), apply some decorative 'wrap' of alloy, wood, or masonry materials to conceal the container frames, and install a commercial window system into the perimeter framing for a finished enclosure. It's possible to repurpose some bare container frames to support a perimeter deck and wide roof overhangs. Similar approaches have been done with industrial T-slot framing, (notably with the It House demo in Josua Tree CA) and I have long worked on the development of a housing system called Utilihab based on this. However, it looks like that kind of framing will never come down in price sufficiently to compete in cost with mainstream housing.

Though often overpriced compared to what a skilled person can do alone, there are now many nice fully-finished prefab container home offerings. One particularly nice line comes from Canada;

Their dual-container module is particularly attractive and would work well in a compound home setting. Another nice one is the Quik House, developed by the NJ design firm of Architecture & Hygiene. These are generally much larger homes and intended to make the most of the industrial look of dry shipping containers.

One of my business partners in Seattle is also working on getting into prefab container homes, though what this company's offerings will be is still unknown.

With all their virtues, container homes do have one big drawback from a DIY standpoint; bulk. Even with the new flat pack container frames, one needs heavy equipment to move them around and a crane or the like to place and assemble them. If you don't live in a region where there is a good routine volume of container traffic, just the equipment to move them around can be prohibitively expensive to hire. Equipment like Container Load Trailers can make this much easier but they are extremely rare and largely unknown in the US.

This is why I spent so much effort on Utilihab. We ideally need high performance building systems facilitating the solitary builder and eliminating heavy equipment. This may have to wait for some very new structural technology, but in the meantime things like Wikihouse are looking promising.

I've recently become much more interested in this project now that it's released some working open source plans and files and have been considering investing in a CNC router of my own and perhaps a new small business. Wikihouse is developing open source designs for small houses based on CNC-cut puzzle-fit plywood construction. It's very similar to the work MIT has recently done but made no effort to move to the open manufacturing arena. Currently, they are developing structures in the Tiny House class of architecture and the market for that has exploded, particularly in the US where people are still reeling from the impact of the Great Recession and the 2008 real estate melt-down. No one want to deal with the banks anymore and Tiny Houses are a logical alternative. Though built-up structures, the scale here is the same as container homes and the structures could be employed in many of the same ways, but without the need for heavy equipment. I would like to explore the possibilities of more modular structural systems and the application of pod-furnitecture and microshelters. I've been working recently with some of Michel's other colleagues on an Urban Nomad project that involves such design;

I think there is also great business potential in this method of construction in that it offers strong potential to supplant conventional stick frame construction, fitting into the evolutionary trends of mainstream housing favoring increasing reliance on engineered lumber materials. I see the possibility here of creating a kind of Amazon Market for the service industry of building houses built around a configurator platform that enables the on-line custom design of modest homes whose freely portable production files can be sent anywhere to produce a home kit in a matter of days. For me, the big problem is where to put this big machine so I can get started experimenting. I may have room for it in my colleagues' facility in Seattle, but I live in New Mexico and probably wouldn't be able to operate it myself as travel is rather difficult."