Thank you for all the thinking, Cody. Let me clarify a few things about my project:
1. Not using any concrete in my mix. Am using newspaper, water, clay, a small amount of flour, a small amount of lime, trash bags full of cut human hair that I'm collecting from barber shops/hair salons, a small amount of straw, a small amount of boric acid. The mixer turns it all into a thick mud with lots of fibers. Am testing and experimenting with mixes and haven't settled on final proportions yet using the free materials at my disposal and the clay on my site. May also need to add a bit of screened sand. We'll see. People using a similar mix in the Truth or Consequences and Deming areas have tested r factor of 1 foot thick walls of this and found it is right about 35. They are mixing prickly pear cactus paddles in with their top coat mix, which is proving to be a really effective sealant -- for up to about 10 years so far. You can pour forms on flat ground of this mix and create blocks or panels. Or you can pour it directly into wall forms and tamp them and let them cure. Takes a couple weeks to cure in the New Mexico environment. When it does, the blocks and panels are quite light. Not as light as foam, but not far off. These things are mostly air and expanded cellulose with a little bit of clay and fiber and flour helping hold it altogether. I'm expecting the 4'x8' panels, 6" thick, to weigh about 12 pounds cured. These are NOT load supporting walls. They are simply super efficient insulating -- sound deadening walls that are proven to be highly fire resistant. They can be made to smoulder if you hold a torch to them for three minutes. But the fire does not spread more than an inch or so from the point of the torch flame. The boric acid is a fireproofing compound -- non-toxic -- and so is the clay . And the building materials -- besides being practically free -- are non-toxic,. do not outgass, and with a sealant coating of something like a lime-clay plaster or the prickly pear juice claycrete mix, tend to shed water well. At least as well as adobe plasters. Most roofing tars are basically a mixture of two types of clay plus some asphalt and fibers. This is not that different, just no petroleum products added to the mix. This would not work in a wet climate like I lived in on the East Coast for six years where we got 70 to 80 inches of precipitation per year. But, like adobe, should do well with the average of 10 inches of precipitation we get here. And others here using the material have been reporting good results for a decade. I want foot thick walls. I like foot thick walls. And I want the high insulation and high heating - cooling efficiency that affords. And I want to build the thing light. I want it to be possible for one or two people, with very little specialized equipment, to be able to lift and put in place every single of it. (That won't be possible with the larger model when I build it, because I'll be using scrap-yard rebar and welding a truss-like frame for it. (Uprights, cross beams, second floor deck and the actual roof rafters.) And that will require rigging a crane-like device and block and tackle, etc. in order to move some of those and get some of them positioned. But once the frame is in place and welded solidly, the remaining pieces should all be a relatively comfortable lift for one or two people -- and especially using a block and tackle set up to lift the second floor panels into place. At least that's my thinking right now. Experience may prove me wrong. But first test is a much smaller scale, foam cored version of the 8-foot-tall-wall hexayurt that provides 166 square feet of floor space. Mine will have a little less because I'll have an additional six inches of insulation on the inside of the walls. I know it would be much more traditional -- and a surer bet -- to use metal roofing on plywood. But people are getting away with the papercrete panel roofs here. And they provide extraordinary insulation. And I want to experiment with that. If that fails (and the building doesn't collapse and I'm still around to talk about it, I'll talk about how to add metal roofing then). I am going for a permanent install. I'd like to see the building (with about the amount of ongoing maintenance you would do with a traditional adobe) last 30 to 50 years. Or longer. So I do want a true footer. And the footer often is the weak point in rammed earth and adobe construction. If moisture collects there, the building basically loses its integrity. Newcomers to this area love to buy 100- and 200-year-old adobes. They are charmed by them. Until they own them and discover all the retro work they must do to save the structural walls and supports any place there has been a water collection problem over the years. Current building standards in New Mexico solve that by requiring a non-adobe footer either one or two feet above the ground, don't recall which it is. The French drain sort of footer I described doesn't meet code, I don't think, but seems to be effective and is certainly much less expensive than excavating and pouring a foot thick cement footer almost four feet deep and two feet above the ground. I'm wondering if its really necessary, though, with a buildling as light as what I'm planning (the small, first pod). Am thinking if the site is graded well so water drains away from the building, water coming off the building is diverted to catchment, and I have the base of the walls sitting a foot off the ground on well-compressed sandbags. Doesn't that pretty much remove most threat of moisture migration into the walls?. That could be further protected against by painting the bottom sides and maybe bottom six inches of all the panels with roofing tar. And, I may be wrong, but I think the sand-filled bags would be plastic enough to compensate for the flexing caused by ground contraction and expansion during the freeze and heat cycles. ----- Here's some photos of one person who has been pioneering with various forms of paper aand clay adobes (and he often has added Portland cement to his mix. Not everyone does.). https://picasaweb.google.com/denisthursby06 And this is not a "beautiful" photo, but it shows a papercrete composition roof on one of his houses. (This one does use a cement layer.) https://picasaweb.google.com/denisthursby06/MMcCainSOriginalHouse2005NewMexicoUSA#5250855558722987170 Cody, please say more about "builder adhesive" and "stress skin panel." I don't know what either of those terms refer to. Thanks again for all your input. I've been away all afternoon and notice you've made quite a few comments. This is the first one I've gotten to. Hope I've clarified what I'm up to and my intentions for the project here. Obviously, I'm excited to be geting underway with it finally. Best, ken winston caine ----- Original Message ----- From: Cody Firestone To: [email protected] Sent: Tuesday, July 26, 2011 3:39 PM Subject: Re: [hexayurt] Harbor Freight sells hot knives -- and questions re: my plans for the footer i would suggest using ground contact treated 2x4's secured to the ground with stakes. Rebar should work for several years. Basically a ring around the bottom of the footprint of the Hexayurt. You could use the builder adhesive. I've made stress skin panel out of it for years. Has you considered that? You could also make a stress skin panel out of sheet steel, and use your window flashing and adhesive as the bridge over the gap. This would be lighter, i think, than the clay/concrete? i also think a metal exterior would shed snow rather well and you could get it in all kinds of pretty colors. I think having the inside covered with something fireproof is essential to long term habitability, otherwise it can be a significant fire hazard. I've done 3/8 inch sheet rock / 2 inch foam / 3/8 inch plywood exterior in other structures to good use. You can use the flashing, with the "l" or "t" side between the panels, and that will also add considerable rigidity and strength. Another consideration is the expansion and contraction of the clay/concrete overcoat. I do not have the co-efficient of expansion and contraction difference. however since that can become a problem in conventional foundation construction, You may end up with a flaking off of the clay/concrete over time. Particularly with a monolithic coating. If you use SIS panel, the "spacer" of the adhesive and flashing could help to allow for expansion and contraction. I know that the foam is designed to have a similar expansion / contraction relationship with plywood. Here is more than you ever wanted to know about plywood : http://home.howstuffworks.com/plywood.htm Some projects require that you use or at least understand plywood. This material is a very popular construction tool, because the layering of thin sheets of wood gives it great flexibility and strength. Knowing about plywood can save you money and may mean the difference between a successful project and one that fails. For example, you don't need to buy an expensive piece of plywood that's perfect on both sides if only one side will be seen. Similarly, there's no sense in paying for 1/2-inch thickness when 3/8-inch plywood is really all you need. Plywood also comes with different glues, veneers, and degrees of finish. By knowing these characteristics you may be able to save money as well as do a better job. Plywood is a commonly used material because it resists shrinking and cracking. Available at home centers, hardware stores, and lumberyards, plywood is better than lumber for some jobs. It is strong, lightweight, and rigid. Its high-impact resistance means plywood doesn't split, chip, crack all the way through, or crumble; the cross-laminate construction restricts expansion and contraction within the individual plies. Moreover, you never get "green" wood with plywood. When you buy a sheet of plywood, you know exactly what size you're getting, unlike with other types of lumber that have nominal and actual measurements. For example, a 4 X 8-foot sheet of 1/2-inch plywood measures exactly 4 by 8 feet and is exactly 1/2-inch thick. Plywood is broadly categorized into two types: exterior and interior. Exterior plywood is made with nothing but waterproof glue and should always be used for any exposed application. Interior plywood, made with highly resistant glues, can actually withstand quite a bit of moisture. There is interior plywood made with IMG (intermediate glue), which is resistant to bacteria, mold, and moisture, but no interior plywood is made for use outdoors. When purchasing plywood, look for a back stamp or edge marking bearing the initials APA or DFPA. APA stands for American Plywood Association, while DFPA is the Douglas Fir Plywood Association. These two organizations represent most of the plywood manufacturers, and they inspect and test all plywood to ensure quality is high and grading is accurate. The most critical plywood grading category for most home projects is the appearance grade of the panel faces (see the chart on plywood grades below). PLYWOOD GRADES Interior Grade Face Back Inner Plies Common Uses A-A A A D Cabinet doors, built-ins, and furniture where both sides show. A-B A B D Alternate for A-A. Face is finish grade; back is solid and smooth. A-D A D D Finish grade face for paneling, built-ins, and backing. B-D B D D Utility grade. One paintable side. Used for backing, cabinet sides, etc. C-D C D D Sheathing and structural uses such as temporary enclosures, subfloor. Unsanded. Underlayment C-plugged D C,D For underlayment or combination subfloor-underlayment under tile and carpeting. Exterior Grade Face Back Inner Plies Common Uses A-A A A C Outdoors, where appearance of both sides is important. A-B A B C Alternate for A-A, where appearance of one side is less important. Face is finish grade. A-C A C C Soffits, fences, base for coatings. B-C B C C For utility uses such as farm buildings, some kinds of fences, base for coatings. C-C plugged C-plugged C C Excellent base for tile, backing for wallcoverings, high-performance coatings. C-C C C C Unsanded, for backing and rough construction exposed to weather. Here is a link to the Owens Corning Product page, The 250 Formula of the pink foam is superior than the "150" formula used in wall installations. The 250 is designed for direct contact with soil / concrete / etc. and is more rigid than the 150 formula which. http://secure.owenscorning.net/Portal/uploads/document/20051110/43522-E.pdf -- You received this message because you are subscribed to the Google Groups "hexayurt" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/hexayurt?hl=en. -- You received this message because you are subscribed to the Google Groups "hexayurt" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/hexayurt?hl=en.
