Conex Boxes and Tiny Tree Houses

I'm still just a tire kicker, but dig the wealth of info you other permies have to offer - thank you!
So - I have a wee plot of land to build on, and am looking at using a conex shipping container to store my stuff and live in while I build. That seems tiny to me, so I trust I'm in the right place to ask: any experience with this? Suggestions on venting/airflow? Insulation? Keeping critters out when the door is open so I don't suffocate in the heat?

And secondly, and good reference material on building tiny tree houses?

Thanks again!

~ Keith
SE Tennessee

Hi Keith,

While I haven't built a dwelling out of a shipping container, I was quite taken with the idea a couple years back, and did quite a bit of reading. Are you familiar with http://www.residentialshippingcontainerprimer.com/ and https://renaissanceronin.wordpress.com/? Some fluff on both sites, but also some good information.

Though I've moved on from planning to build a sea can house, I bought a 20' highcube for use as a workshop/storage space this spring, which has worked out well so far. I intend to add another container later, and use them as supports for a larger workshop.


I'll try to hit the high/low points as I recall them from my research.

The main thing that put me off the sea-cans for a dwelling was the difficulty of really utilizing that wonderful, tough, impermeable steel skin. Unless you are building a larger structure around the can, you really have two basic choices; insulation inside, or insulation outside. I ended up deciding I didn't like either choice very much.

If you insulate inside, you make the space smaller. Length is no big deal, but width and height are. A 20' can is about 7'-8" inside; even 3" of insulation and a thin skin inside that will bring you down to barely 7'. Height is only a bit more, so again, squeezing an already tight space.

If you insulate outside... well, that steel shell just doesn't strike me as the ideal interior wall, and now you need a weatherproof exterior wall anyhow. At this point all the container is providing is strength. Plus, you've got thermal bridging to worry about; you need your insulating shell to be very complete, because anywhere the can is exposed to outside temps will be a major thermal bridge.

The best system IMO to address this is he one that the renaissanceronin site advocates; to have closed-cell spray-foam applied to the entire outside of the can, and then attach siding to studs imbedded in the outside of the spray-foam, relying on the foam to hold this all together rather than accepting the cost in time, dollars, and thermal bridging of securing the studs via bolt/screw/weld to the can itself. The doors would be somewhat more challenging.

Either way, you will be relying on forced air for ventilation... I'd be worried about condensation/mold issues with the insulation on the inside, too. To mitigate, I'd want to use something that is NOT fibreglass batts, as mold resistant as possible. Perhaps rockwool, or rigid insulation board if you are comfortable with possible offgassing in an enclosed space like this.


I still think containers are a great resource, but just don't see them as very well suited to living in. To do it right seems to involve enough work, and compromises, that other options seem preferable. For a workshop/storage space I think they're great.


What about going ahead with the container as secure storage, and living on top of it in a tent, or walltent, or tiny yurt? Seems like it would make an awesome tent platform, out of reach of most critters. Ideally you could connect the top of the container to your treehouse with a bridge/ladder...


Keeping critters out, I assume you mean the small flying sort, I really don't see any option except a screen wall right inside the doors.


As far as treehouses go, all I can offer is a suggestion to look into treehouse attachment bolts or garnier limbs as a starting point. There's a bit of info here: http://treehouses.com/joomla/index.php/construction/treehouse-layout

Thank you for the great resources. The drawbacks you referenced were the same I had concerns with, so your advice was on target. I like the suggestion of using a conex as a platform to live on top of and then build from there.
Thanks again!

buying a refrigerated container solves the insulation problem.

Much depends on your climate and things like how long you expect to live in it.

Another option would be to bury the container in earth and basically make a WOFATI structure of it. You'd still have to cover it with an EPDM liner and some sort of insulation like wool felt under that, and rust from condensation could still be an issue. It may be better in the long run just to build a pole structure WOFATI. That will breathe, unlike steel, and for the $2,000 - $3000 you'd spend on a container, I think you could easily build a complete Wofati.

Hi Keith, glad it helped. I'd love to see what you end up doing, treehouses might not be the most practical of builds, but they're just so neat!

Rose I would agree that if *fast* shelter is the imperative, a well insulated freezer can is a good option for reasonably short term living space in some climates. If you're willing to live without any window/doors except in the door end of the can, and with exposed wiring/ducting inside, it could be inhabitable in very short order.

Issues:
1) If you want any added windows or doors, cutting and welding just got more complicated and unpleasant. Ditto for modifying containers to connect them together, and for any repairs your can might need.
2) Space; reefer cans must be the same dimensions as regular cans on the outside in order to interlock, so the insulation space comes right out of you living space, just like internal insulation in a standard can..
3) They're not necessarily very well insulated; 1-3 inches of EPS or CPS seems to be the range. 1" of EPS is around R4. 3" of XPS is around R15, which isn't too shabby. But that 3" all around would cost you 6" of interior height and width...

Joe DiMeglio wrote:Another option would be to bury the container in earth and basically make a WOFATI structure of it. You'd still have to cover it with an EPDM liner and some sort of insulation like wool felt under that, and rust from condensation could still be an issue.

Please don't do this! Containers are very strong top to bottom in very specific ways. They are not strong enough sideways to bury in earth! See here: https://renaissanceronin.wordpress.com/no-isbu-peek-a-boo/

One *might* be able to build a buried wofati-esque structure using a seacan as a central support for a load bearing sloped roof, allowing you to avoid any sideways pressure on the walls of the can. You'd need to actually do the math to confirm if this could work, though. It would need a weight distribution system atop the can, as the strength is concentrated on the corners where the containers interlock. AFAIK the middle of the roof is no stronger than the walls, and the edges only somewhat so. Of course, there would be a number of complications to address even if the design was technically strong enough.