Note: This page is very much related to Hexayurt_Thermal_Analysis.
Walls and Roof
- Tuff R/Super Tuff R - Quick-and-dirty units constructed directly from materials purchased at Home Depot or Lowes. That's what we did at Strong Angel.
- OSB Board - with precision cutting of angles for tighter assembly. That means a table saw. Ideally we'd find a local wood shop and have them cut for us because: I'm, er, not the guy to be doing that work, and keeping my fingers!
- Dow Thermax HD - Higher spec materials which may need some wrangling to obtain. Two or three inches thick, better foil facing, generally much more like what you'd use in disaster relief situations.
- Hexacomb cardboard - (http://hexacomb.com/) which can be manufactured on site from flat pack core materials, so the 1"x4'x8' board is made from a core about two inches by six feet by one inch, and a couple of rolls of foil. Hard to explain, see the "Rapid Deployment Concept" page on http://howtolivewiki.com/hexayurt/
- Waterproofed Triplewall Cardboard - Weyerhauser has a really good waterproofed triplewall cardboard, as used in the Global Village Shelters. We're trying to source some but having problems, but of all the materials, it's probably the one closest to spec for developing world use if somebody wanted to start making units ASAP.
Plywood / OSB
https://web.archive.org/web/20100712052444/http://opensourceecology.org/weblog/?p=340 - $132 plus paint for 166 square feet. Unbeatable. and there's a ton of unedited video and pictures here:
I think there's scope for an approach here where there is no flashing used, but (for example) the roof triangles over-lap a few inches at the center of each triangle and screws hold the boards together, and at the roof edges, the roof goes over the lower of the two boards comprising the roof triangle, and is screwed directly into place.
Could be hell to waterproof, could have structural problems, but my intuition is that there's an approach here which does plywood with no fasteners beside screws/nails which might be very useful for some circumstances.
Andrewed says: Here is a prototype of an OSB hexayurt made with permanent plastic hinges. Worked really nicely.
4 roof panels and 2 wall panels, all with miter-cut edges, are joined permanently, Danger Hinge-style. Then these sub-assemblies get assembled into a complete building with the "opening" hinges. See each picture for detailed caption.
The plastic hinge is made from propaflex. See:
propagroup.com > impact and handling problems > propaflex
It comes in rolls with the thin creases running perpendicular to the length of the roll. I just cut it at every second crease to make the hinges.
It is cheaper than standard plastic hinging and it works. It is a little weaker, so I worked out a trick to prevent tearing at the ends. Just trim the end of each piece so the thin, bending part in the middle sticks out beyond the thick flaps, like this:
___ ______/ | \______ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |_____ | _____| \_|_/
This is generally not a recommended approach because for most applications, polyisocyanurate boards with aluminum facing are a better bet for long life and insulation properties. However, should you wish, here's how to do it.
I had a little think about coroplast again, and spotted two things I have missed the first time we looked at coroplast.
We can now offer a pre-fab or field-fab hexayurt which folds up very much like the existing folding units. The mechanism might change just a little on the roof.
As a bonus, the coroplast hexayurts can be fastened with pop-rivets rather than tape, which cuts the price even more. Pop rivets are five cents each, and we'd use one about every six inches. They go in with a cheap manual tool or a power tool.
The trick for strength is that for the roof, where two panels come together, you take about four inches of each panel and make a crease. The panels are put side by side, with the 4" strip bent up at 90 degrees to each panel, forming a fin.
Those fins then re-enforce the roof from wind loads.
That fin - that vertical ridge - is then folded over in half, forming a 2" fin - and pop-riveted in that position. This connects the two panels, and and produces a structural reinforcing fin which is also watertight because there is no route for water to enter the building's roof, except by going up the fin, through the tight folds, and into the building.
A similar approach can be taken at the roof edge, incidentally producing a Rainwater harvesting gutter if done right.
Taking down the hexayurt would be a matter of using bolt cutters on the rivet (light ones, maybe even tin snips) or just ripping the rivets through the material - note the holes would only be in the fins.
With a little additional work, I'm also pretty sure we could make this entire assembly fold. There might be some fiddly little cuts or creases in the coroplast to make it work, but nothing you couldn't do with a craft knife or a hack saw. We could also spec an 8' roof pole to go into the center of the space, which removes all and any structural issues about the coroplast permanetly by putting it in tension, and it will simply never tear in that configuration (*very* strong in tension). I should have thought of that before.
Or consider the IcosaPod direction, and use ?triangular? box girders on the structure. They could, for example, be fabbed on the edge of each panel, or possibly done as separate items. Might be a good way of getting the roof pole also.
- Bidirectional filament tape, 6" wide. Available from DistributorTape (ABT TRADING GROUP, Inc.), or by phone at 1-786-565-9858. Also available at Amazon: WOD FIL-835B/D.
- Ideally we need a one-stop tape; a duct style waterproof, bidirectional filament tape with a foil face.
Leather can be used on top of the OSB roof panels see the 2008 Hexayurt at Open Source Ecology.
Raised & Leveled Sand/Earth + Sheet Plastic or Tarp + Insulating Board + Plywood or Board (+ Carpeting or Mats) (Toczko Floor1)
The idea is create a level, dry, insulated floor that will support the weight of furniture legs and appliances, etc.
- First, to keep water out, prepare a level raised sand or earth surface, surrounded by rocks, cinder blocks or other material to keep it from spreading out. A ring of cinder blocks or rot-resistant wood staked in place with pieces of rebar would work. This is where the walls of the structure will sit, and where water will run off away from the structure, so we want the edge of the wall to be at the outer edge of the raised surface. Place the outer edge level. Fill the cinder blocks with sand or earth, if we are using blocks, and then fill the center area with sand or earth and level it with a long straight piece of wood, or scrape the high areas with the edge of a sheet of plywood until the floor is as level as we want it. (If you think that later on we will wish that we'd spent more time leveling the floor, then do that now :)
- The next layer is a one-piece sheet of plastic to keep moisture out of the structure. It doesn't need to be strong thick plastic because its not going to be exposed to wear and tear if we use the insulating board and plywood layers. if the plastic is going to be the top layer then yes, we do want the strongest plastic sheeting or tarp we can get. The plastic should extend out over the edge of the floor, and over the edge, to let water run off and away. (I'm assuming a tropical rain forest in a typhoon, or a winter flooding rain storm that goes on for a week. The sort of conditions that warrant building emergency shelters.)
- The next layer is insulating board, if we are in a cold environment. In a warm climate we probably don't need this.
- Plywood or board layer. This can be cheap thin sub-flooring, or scrap 2x4, or any flat material strong enough to support a furniture leg pressing on it. This could also be optional if we aren't going to be using that kind of furniture, or if there isn't any insulating board layer.
- Comfort layer: Carpeting, mats, blankets, etc. Whatever we have on hand, or whatever we want to use and can plan for.
If we make this floor with all the layers we have a surface that feels and acts like a standard Western floor: Carpeted, warm and dry, that we can sit a chair on and rock back and not poke holes in the insulated floor.
1 First described to me by my friend Greg Toczko as a geodesic dome floor.