• Post Reply Bookmark Topic Watch Topic
  • New Topic
permaculture forums growies critters building homesteading energy monies living kitchen purity ungarbage community wilderness fiber arts art permaculture artisans regional education experiences global resources the cider press projects digital market permies.com all forums
this forum made possible by our volunteer staff, including ...
master stewards:
  • Nicole Alderman
  • raven ranson
  • Jocelyn Campbell
  • Julia Winter
stewards:
  • paul wheaton
  • Burra Maluca
  • Devaka Cooray
garden masters:
  • Anne Miller
  • Pearl Sutton
  • Joylynn Hardesty
  • Shawn Klassen-Koop
gardeners:
  • Joseph Lofthouse
  • Bill Crim
  • Mike Jay

Cob, earthbag or straw bale? Which is best?  RSS feed

 
Posts: 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
We live in Alabama where we mainly have hot and humid weather with maybe 2-3 months of chilly weather around the 20s or 30s, give or take. We rarely have snow but freak occurrences do happen and we get about 57" of rain annually.

Our budget is tight (under $1,000) and our timeline is short (2-3 months max).

We dug down about 1.5 ft and did a jar test (see image) but I don't know if we did it right and if we did, I'm not sure if we have decent site soil to build with. Thoughts? If we don't, what kind of clay and sand do we need to buy? How many tons of each for a 200-300 sq ft house with 8' tall walls on the front and 6' tall walls on the back?

Do we need a rubble trench or can we build the house on an above ground foundation such as a deck? If a trench is best, what kind of gravel and pipe do you all recommend? Is a 1/4" drop per ft good enough for the slope?

Any and all advice is greatly appreciated!
20180519_094007-01.jpeg
[Thumbnail for 20180519_094007-01.jpeg]
 
gardener
Posts: 810
Location: Ohio, USA
107
dog fish food preservation forest garden fungi solar trees urban woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I live in ohio.  People have tried cob here.  It's fun to watch it melt slowly over the years because of the moisture here.  Cob, like its sister Adobe are meant for dry conditions.  Even soil cement, which I experimented with,  melts here and it probably would in other wet climates.  Cob is ok for indoors here though. I thinki straw bale might be similar because it usually has a breathable cob exterior. How's your supply of pallets?
 
pollinator
Posts: 2019
Location: Cincinnati, Ohio,Price Hill 45205
69
forest garden trees urban
  • Likes 1 Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
With that budget,I would use tires.
I would cut off the sidewalls,lay them out, fill with soil, ,compact with shovel,stack the next course,repeat.
Build a scrap lumber and discarded plastic roof, topped with used carpet to protect the plastic from UV  exposure
Screw layers of cardboard and plastic to the tires, inside and out. Finish with pallet wood.
Potentially only need to buy an impact driver,bit, screws and shovel.


 
pollinator
Posts: 252
Location: Stevensville, Montana; Zone 5b
36
food preservation forest garden hugelkultur
  • Likes 5
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Cob Cottage Company is based in Coquille Oregon which gets an annual 55" of rainfall each year and their buildings are in perfect condition. Cob is more than suited for wet weather you just have to protect them adequately. Get the "hand sculpted house" by Ianto Evans or "The Cob Builders Handbook" by Becky Bee; i've put both links below. You need to have a good "hat and boots" which means build up your water impermeable stemwall well above the ground and make nice big overhangs for your roof, think 2-3 feet.

https://www.amazon.com/Hand-Sculpted-House-Practical-Philosophical-Building/dp/1890132349/ref=sr_1_1?ie=UTF8&qid=1527609526&sr=8-1&keywords=cob+house

https://www.amazon.com/Cob-Builders-Handbook-Hand-Sculpt-Your/dp/0965908208/ref=pd_sim_14_2?_encoding=UTF8&pd_rd_i=0965908208&pd_rd_r=39DJZ1QHAZFRBPF56TXE&pd_rd_w=1Kj6g&pd_rd_wg=Ab2Dl&psc=1&refRID=39DJZ1QHAZFRBPF56TXE

Cob will be too heavy for a platform build house, you need a rubble trench foundation and that will definitely help with drainage. Again, I highly recommend the books mentioned as they outline all the questions you might possibly have about cob. 3 months is short, but doable if your design is 200-400sq feet. Get some friends together for a building party. I would recommend building with strawbales just for speed. You could stack all your walls in a week. The gravel for rubble trench can be anything, sharp gravel needs much more compaction than round drain rock.

Make a few test cobs--like brick size--with the soil you have and see how it fairs to dropping on the ground. As for tons, do the math for volume with your walls. 7' average wall height at 2' thick with a run of 70' of wall is 980 cubic feet of material. That is about 35 yards of material at 1 ton each.  This answer was brought to you by the really rough estimate organization, where we estimate things that cannot be properly determined from my work computer.
 
Posts: 204
2
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Daniel Ray wrote:Cob Cottage Company is based in Coquille Oregon which gets an annual 55" of rainfall each year and their buildings are in perfect condition. Cob is more than suited for wet weather you just have to protect them adequately. Get the "hand sculpted house" by Ianto Evans or "The Cob Builders Handbook" by Becky Bee; i've put both links below. You need to have a good "hat and boots" which means build up your water impermeable stemwall well above the ground and make nice big overhangs for your roof, think 2-3 feet.

https://www.amazon.com/Hand-Sculpted-House-Practical-Philosophical-Building/dp/1890132349/ref=sr_1_1?ie=UTF8&qid=1527609526&sr=8-1&keywords=cob+house

https://www.amazon.com/Cob-Builders-Handbook-Hand-Sculpt-Your/dp/0965908208/ref=pd_sim_14_2?_encoding=UTF8&pd_rd_i=0965908208&pd_rd_r=39DJZ1QHAZFRBPF56TXE&pd_rd_w=1Kj6g&pd_rd_wg=Ab2Dl&psc=1&refRID=39DJZ1QHAZFRBPF56TXE

Cob will be too heavy for a platform build house, you need a rubble trench foundation and that will definitely help with drainage. Again, I highly recommend the books mentioned as they outline all the questions you might possibly have about cob. 3 months is short, but doable if your design is 200-400sq feet. Get some friends together for a building party. I would recommend building with strawbales just for speed. You could stack all your walls in a week. The gravel for rubble trench can be anything, sharp gravel needs much more compaction than round drain rock.

Make a few test cobs--like brick size--with the soil you have and see how it fairs to dropping on the ground. As for tons, do the math for volume with your walls. 7' average wall height at 2' thick with a run of 70' of wall is 980 cubic feet of material. That is about 35 yards of material at 1 ton each.  This answer was brought to you by the really rough estimate organization, where we estimate things that cannot be properly determined from my work computer.



I have read a lot about cob being used in England, which is probably wetter on the average than most places in the U.S.
 
Amit Enventres
gardener
Posts: 810
Location: Ohio, USA
107
dog fish food preservation forest garden fungi solar trees urban woodworking
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Well, maybe whomever does it here doesn't do it right, but even the old masonry structures here need regular tuckpointing or they'll crumble. When I lived in California, some of the oldest buildings, if not the oldest buildings, were adobe and I saw some nice cob.  Not so here.  Could be a combo of high humidity, windy storms, and strong freezes... I'm not an expert.
 
pollinator
Posts: 1943
Location: Toronto, Ontario
145
bee forest garden fungi hugelkultur cooking rabbit trees urban wofati
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
I imagine a freeze-thaw cycle is the culprit. If ambient humidity saturated the outer layers of cob and then froze, the moisture would expand, probably causing some of the material to slough off.

I think that a proper roof overhang takes care of most moisture-related cob issues, and sealing that with a natural hydrophobic plaster might do wonders, too.

I would suggest reclaimed cinderblock before tires. Hell, I'd suggest a conventionally built building before tires.

Which is best depends on your goals. I would probably look to a rubble trench foundation and earthbag, if I wanted something bullet-proof, or a pallet structure cobbed on the inside and with that aforementioned hydrophobic natural plaster on the outside(I think it's essentially cob that's treated with olive oil at a certain stage in the cure).

In either case, I would overbuild on the structure to put a bigger hat on it than strictly necessary. I would also design and orient the structure in such a way that it harnesses the prevailing wind to promote airflow around the building, which might help keep the ambient moisture levels around the structure low.

-CK
 
author
Posts: 39
Location: Silver City, NM USA
15
books solar woodworking
  • Likes 1
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
If I were in your shoes I would go underground, or at least substantially bermed, in your climate. The year-round underground temperature is between 65 and 70 degrees F., a very livable temperature, without need for heating or cooling! Of the three options you are considering, the only one that should be employed below grade is earthbag. With this technique, the exact composition of the soil is not nearly as critical as it is with cob or plaster for strawbale, so what appears to be very little clay in your soil is not a problem. Also, it is conceivable that a very small underground home could be built for very little money with earthbags. You greatest expense will be for a good roof. There are many underground/bermed house plans shown on my website at http://dreamgreenhomes.com/styles/earthsheltered/earthbermed.htm
 
If you like strawberry rhubarb pie, try blueberry rhubarb (bluebarb) pie. And try this tiny ad:
One million tiny ads for $25
https://permies.com/t/94684/million-tiny-ads
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!