I’ve been corresponding with one of our readers in New Zealand about low cost, alternative cabin building ideas with disaster preparedness in mind. We’ve talked about a whole range of ideas such as using straw bales for energy efficiency. The design presented here is DIY friendly, affordable, suitable for a grid-down situation and can be easily moved if desired.

Just like any location, New Zealand has some challenges that must be addressed when designing a home or cabin. Design challenges here include earthquake resistant construction, adequate insulation, and selecting materials that are available in more remote areas. In this situation it has to be owner-builder friendly, reasonably affordable, and portable in case the owner ever wants to move it.

Here’s a brief summary of the ideas we’ve hashed out so far:
– Pour a concrete or soil cement slab on top of rigid foam insulation and with insulation around the edges.
– Make DIY double arch trusses using a pipe bender and chain link fence top rails. If you’re not a welder, you can flatten and drill holes in the ends of the web members and bolt to the arches. The arches are bolted to short pieces of slightly smaller or larger pipe that’s buried in the slab. These homemade trusses provide reasonable resistance to quakes for small cabins. Square or rectangular tubing are options that are easier to screw to.
– Attach steel rails and durable metal roofing on top of the trusses with self tapping screws.
– Install outlets and any other desired mechanical components such as fans, cabling, etc.
– Frame in a window wall on the end that faces the sun (north facing in NZ). Make insulated curtains to seal off this wall at night to conserve energy.
– Frame in the other end wall of this arched cabin to join a pre-built unit that contains all of the mechanical systems as explained in this previous blog post.
– 8” of sheeps wool insulation is approximately equal to straw bales but without the drawbacks of losing space, etc.
– Add wood T&G or lap siding on the interior.
– Design the cabin with counters, closet, sofa/bed and desk along the outside walls so you have more headroom. Study tiny house videos for space saving ideas. Use throw rugs down the center area so the floor is more comfortable.
– The cabin can be hoisted onto a trailer after unbolting the trusses where they connect to the slab. The mechanical unit can also be removed and transported elsewhere.
– The owner said it would not be difficult to get this design engineered and approved. (No chance of building without a permit in case you’re wondering.) The owner also would like to use 12V wiring because it doesn’t require the services of a licensed electrician.


Comments

New Zealand Bug Out Cabin — 12 Comments

  1. Owen

    Just wanted to recap/clarify a couple of points and thoughts. What OD pipe are you thinking for the trusses? There is from from 1 3/8″ up to 4″ available.

    Rather than J bolts sink a piece of pipe with a bolt thru it close to the end as an anchor into the stem wall. Do I need just to anchor one side of the truss to the stem wall or both ends?

    The systems container really works well as I can put a lot of things inside to keep the size of the actual insulated living space small. So items like a washer, dryer, or a chest freezer which might normally be luxury space items for a tiny home are not an issue, This also helps keep wiring simple inside the structure and 240V only needed in the container. 10ft containers cost as much here as 20ft so I can have a 20ft container for the same cost. I can either butt the end of the container up to the truss building or attach on the side of the container installing a side man door. It would be like having an above ground basement or garage. I could even attach the living space to the container for stability.

    Do i need any kind of thermal barrier between the clay bricks and the stem wall? Wasn’t sure if the sand was enough.

    On the window wall, can I use a ranch slider instead of a normal door? Solar gain would be high plus no weight of a door on the structure or hinges to wear out or sag over time. Also they are readily available used here, often pretty cheap.

    I guess that is my hundred questions for now.

    Many thanks of all the insight and sharing of your knowledge.

    • You can fit the trusses onto buried pipe like I said above. The better way is to weld plates on the bottom of the trusses as shown in the photo and use anchor bolts — one on each end (2 total per truss).

      The engineer will determine the pipe size based on calculations, but somewhere around 2-1/2″.

      Thermal barrier: depends on how cold it gets. In a place like Canada you would want this.

      Slider: sure, no problem. Pressured seals and weatherstripping often wear out on used doors. Best to buy new if you can afford it.

  2. Owen

    Doing some costing estimates. What is your best guess at arch spacing? I need to know how many arches I will need. I thought I would do 10ft (3 meters) wide. A 2 part joined in the middle arch. I will have to get a structural engineers approval for consent but for estimating purposes your guess would be pretty close a lot better than mine.

    • So you want 10ft wide space on the interior? 10-12ft wide interior is a good size.

      Spacing of trusses depends on seismic load, building codes, snow load, size of horizontal rails, etc. etc. A 4 ft. spacing like in the photo looks good.

      • Owen

        You are a mind reader. Exactly what I was thinking was recycled clay brick infill. Should also give me a good thermal mass floor plus I like the looks of them. No stress or earthquake cracks to worry about either.

          • Owen

            Good point. That will be easier in the future with the clay bricks as compared to a sealed concrete slab.

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