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Gambrel wofati?

 
Paul Bonneau
Posts: 13
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I like the gambrel form both for esthetic reasons (looks more cozy than rectangular forms, probably because humans lived in caves for so long and it looks more cave-like) and because of the forces involved it eliminates the need to bury posts with all the attendant rot problems. The following crude drawing is looking upslope.



The layers are:

sand (mainly to hold the epdm down and protect it from the sun, fairly thin layer to avoid a heavy roof)
epdm
loose straw
tyvek
wires, OSB, or whatever structural components

At the back of this house there will need to be excavation and trenches as with Oehler, but less of it because the house is narrower in the cross-slope dimension than it is in the upslope-downslope dimension. The pressure of the compressed straw and whatever snow loads there are act to press the lower roof in a way that is stable and does not need post holes to counter those forces. The water runs down the local (house) slope until it gets to ground level, then turns 90 degrees and continues down the major slope.

The red items are substantial logs, maybe 20 to 30 feet long. Assume the major logs are labelled 1 through 5, going from left to right (1 and 5 will be sitting on concrete foundation blocks). Between these logs are shorter vertical logs (blue lines) which support the upper structure. The correct angles (I like the angles of a regular gambrel, 135 degrees at each log, even though the drawing is not accurately showing that) are maintained by 3 loops of cable at each end of the major logs. There is a loop between logs 1 and 3; another loop between logs 2 and 4, and a final loop between logs 3 and 5. These loops are not shown in the picture. It's just possible these loops can be removed after the house is built and stabilized, but it would probably be safer to just leave them on (some experimentation is called for here).

No vertical interior logs are needed in the living space. Also there are some other connection between the long logs; I am visualizing the use of fencing wire which is tremendously cheap and strong, spaced about every 2 inches or so, supporting the tyvek. The wire would run from log 1 to log 5 and back again, over the top of the other logs, repeatedly. Some amount of sag should be put in these wires to reduce the strain on them (loads create infinite strain with very tight wires).

Using loose straw means those big round or rectangular bales that all farmers are moving to can be used here. Just buy a few and cart them up to the site and tear them apart, scattering the straw. Great use of a waste product. With the tyvek the straw can dry to the inside and not rot, yet being compressed it should be pretty fire-proof.

All light in this house comes from the endwalls. Substantial overhangs there are possible but too much would reduce interior lighting. Perhaps the overhangs can be greater toward the north and less on the south end.

The EPDM layer is easy because you just buy stock rectangular items and roll it out. It creates a nice large umbrella for long term heat storage, assuming your trenching efforts at the back of the house are deep enough. Neither straw underneath nor sand above is going to cause any punctures in the EPDM; however some thought is probably needed to keep heavy animals with sharp hooves off the house. Anyway EPDM can be repaired if you can get to it.

Comments?
 
Paul Bonneau
Posts: 13
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Now that I think of it some more, I was wrong about the cross-slope dimension of the house. The house itself is small that way, but with all the extra straw and sand it goes much wider. Oh well...
 
Bill Bradbury
pollinator
Posts: 684
Location: Richmond, Utah
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Paul, I love that you are thinking outside the box, but think even further out where the materials are all natural and locally sourced.
 
Paul Bonneau
Posts: 13
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I'm more interested in using cheap farm-type commodities such as fence wire to create a simple, easy-to-build and energy-efficient small home, but others are welcome to play with this idea and adapt it to their own priorities.

Huh, I found an old thread I posted here a while ago in a similar vein. I had forgotten about it...
link

Another thing I'm thinking about is PAHS, or whatever it's called. A couple of trenches next to logs 1 and 5, connected to a collector in the straw just under the EPDM in the center, along with some solar-powered fans to move the hot air from under the EPDM to the trenches. Of course this would require exposing the membrane around this area so it would heat up in the summer.
 
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