tour of cobville

Started by paul wheaton, January 11, 2010, 12:01:21 AM

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Abbynrml

Quote from: MountainDon on January 13, 2010, 03:05:04 PM
......earthquakes in developing countries always seem to have much higher death tolls than quakes in the USA. We are always shown pictures of piles of rubble, rubble that used to be homes before the quake(s) struck.

I would wager that most code enforcement people would say something like:
"Those homes were just merely rubble piled up before the quake."

There is something to be said for the codes. Most are really for our protection.

Don_P

This is the downside of anything goes building.
If cob cannot supply lateral strength, any post and beam frame would have to provide that...


Freeholdfarm

Well, England is where most of the old cob houses seem to be -- how often do they get bad earthquakes?  (I'm thinking not very often, but maybe someone knows otherwise.)  Here in the US, cob is a pretty new building material for the most part.  Does anyone know more about the adobe houses in California and the Southwest, how well they've stood up to known bad earthquakes?

Kathleen

RainDog

Quote from: Freeholdfarm on January 13, 2010, 05:50:02 PM

Does anyone know more about the adobe houses in California and the Southwest, how well they've stood up to known bad earthquakes?


From Earthquake-Resistant Construction of
Adobe Buildings: A Tutorial

Published as a contribution to the
EERI/IAEE World Housing Encyclopedia, www.world-housing.net

"In addition to its low cost and simple construction technology, adobe construction has other advantages, such as excellent thermal and acoustic properties. However, adobe structures are vulnerable to the effects of natural phenomena such as earthquakes, rain, and floods. Seismic deficiencies of adobe construction are caused by the heavy weight of the structures, their low strength, and brittle behavior. During strong earthquakes, due to their heavy weight, these structures develop high levels of seismic forces they are unable to resist, and therefore they fail abruptly. Considerable damage and loss of life has occurred in areas where these materials were used."

Interesting report. It goes on to make building recommendations and covers some improved building technologies.

http://www.world-housing.net/uploads/WHETutorial_Adobe_English.pdf

If someone wishes to build with cob, I encourage them. Go ahead, and have fun. Just try not to kid yourself if you live in a seismic zone. Earthen walls are very difficult to make safe in an earthquake.

I think that's probably enough from me on this subject. I'm harshing everyone's buzz.  n*
NE OK

glenn kangiser

A few of my research notes.

http://www.newsroom.uts.edu.au/news/detail.cfm?ItemId=14005

QuoteOn Wednesday 17 December the half-size model made of earth and bamboo was put to the test on the state-of-the-art UTS shake table, the only earthquake simulator of its kind in Australia.

The four tests were based on the El Salvador 2001 earthquake which measured 7.8 on the Richter scale. The first test was set at 100 per cent intensity, the second at 125 per cent intensity. The third and fourth tests represented the aftershocks that occur after the main earthquake hits and these were set at 100 per cent intensity. Impressively, the model suffered minor cracks but remained standing.

Hickson collaborated with the Head of School, Civil and Environmental Engineering, Professor Bijan Samali and final-year engineering students Luke Punzet and Jean-Michel Albert-Thernet in building and testing the model.

"If this were an actual building then it could have been safely reoccupied without any repair," Professor Samali said. "It is an outstanding success because not collapsing and killing or injuring people is enough to claim success."

Each piece of straw is bonded to the clay working as rebar similar to fibermesh in concrete.  Just because we are not familiar with a building technique, does not mean it is not good.  We have been guided away from natural building and good old technology in favor of new unsustainable technology and profits.  I was talking to Reza Assemi today - a young developer in Fresno who comes from the families of two of our biggest housing developers.  He said it is a shame the way we are building nowadays with planned obsolescence in housing -about 75 years and commercial buildings -around 30 to 40 years. The plan is that that is their useful life with our modern materials then they will be  torn down and replaced.  Earth houses that last 800 years are no longer in the plans.

Earthquake resistant cob/earth building.

http://www.eartharchitecture.org/index.php?/archives/1042-Earthquake-Resistant-Housing.html

A few of my research notes.  Rounded cog walls resist earthquake damage much better than square cornered walls.  There are cob structures in England that are around or over 800 years old.

http://www.seattlepi.com/lifestyle/334487_cobseattle06.html

QuoteUniversity of British Columbia engineers tested cob's earthquake resistance and, according to one account, the test structure survived a simulated 7.4 quake with only minor cracks, even after prior shaking.

Steel does not work well with earth building at least in the clay/earth mix itself.  Reinforced concrete posts and beams are used successfully in modern rammed earth building.
"Always work from the general to the specific." J. Raabe

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glenn kangiser

Fresno Homeless - tent city as of early this week.  About 3 times larger than 6 months ago or less. Note that this is only a small portion of them.









and a partial solution - not that great either - appx 6 feet x 8 feet I think.

"Always work from the general to the specific." J. Raabe

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glenn kangiser

Cob and adobe are different during an earthquake although both methods of earth building.  Cob works as a unit and is very earthquake resistant.  Adobe without bond beams or a restraining timber structure can be subject to failure as they are like a stack of bricks.

India does have some very earthquake resistant building methods with interlocking reinforced bricks and a diagonal method that will resist the shaking.

http://anangpur.org/anangpur.asp?kat=APPROPRIATE%20TECHNOLOGIES&abc=WALLING%20SOLUTIONS%20&cba=57&pat=HOLLOW%20CORE%20INTER-LOCKING%20BLOCKS&tmn=tt

I'm not saying we are all going to go out and build a new house using these methods.  I am saying it does not hurt us to store the knowledge upstairs of how to do it, for who knows when or why.
"Always work from the general to the specific." J. Raabe

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pagan

#32
I think cob would perform better than adobe bricks in an earthquake. This comes from the fact adobe bricks are mortared together, usually with a mud slip, and thus there are thousands of places where the bricks can slip apart. Cob, on the other hand, is a solid mass wall, I remember Ianto Evans calling it "monolithic adobe" because as you build the entire wall becomes one massive structure without joints or places that can be easily broken apart.

dug




poppy

I have read reports that say many of the "houses" in Haiti that collapsed were made of mud bricks.  I'd wager that cob will not be well received down there even though it could be made to work well and cheaply.

Beavers

Never heard of Cob before this thread.  After doing some reading, turns out the hard clay soil I've been cussing while building my house would be about perfect for making cob.  ;D

I'm not sure if I would want to build a house out of the stuff, but an outdoor cob oven does sound like a great project to give cob building a try.

Was also thinking that it might work for skirting under the house, would be easy to pack in around the posts and all the bracing.  I've got about three feet of open space under the house.  Would cob work to close that area in? I'm guessing I would need some kind of gravel filled trench for a footing under the cob.  ???

dug

QuoteDoes poured adobe have straw mixed into it?

I'm pretty sure it usually does

Now I am not suggesting that every reasonable precaution should not be taken into consideration when considering how to safely construct a home, however- one should maintain a proper perspective. If you happen to be at ground zero during a 7.0 quake it may not matter what you built with.

Conversely, many more lives and property are lost due to fire, something mud is pretty impervious to.

I love the look and feel of adobe homes, and would have built one were I not saddled with a bum back.

RainDog

 That's pretty funny!

When it's cold out, every reasonable precaution should be taken by dressing accordingly, however, one should maintain a proper perspective. If the sun goes supernova and the earth flies off its orbit, it may not matter what you're wearing.

I love this thread.
NE OK


glenn kangiser

Quote from: pagancelt on January 14, 2010, 08:46:42 AM
Does poured adobe have straw mixed into it?

I haven't heard of poured adobe but have heard cob called "coursed adobe" by  some building department literature.  I found a reference to it in this book.

http://books.google.com/books?id=88P3boXpscUC&pg=PA39&lpg=PA39&dq=coursed+adobe&source=bl&ots=tQBmMG_t4S&sig=QdBOGbQxeuwJWhB7iFPmLerXkPQ&hl=en&ei=FvhPS9y-J4GqswPLupiHCA&sa=X&oi=book_result&ct=result&resnum=17&ved=0CFAQ6AEwEA#v=onepage&q=coursed%20adobe&f=false

In  general as the clay ratio is higher more straw is used for reinforcement.  As aggregate quantities get to be less the clay shrinks more and that is why it is made into bricks rather than cob.  Cob is more like sandstone when properly made.

Quote from: Beavers on January 14, 2010, 11:54:18 AM
Never heard of Cob before this thread.  After doing some reading, turns out the hard clay soil I've been cussing while building my house would be about perfect for making cob.  ;D

I'm not sure if I would want to build a house out of the stuff, but an outdoor cob oven does sound like a great project to give cob building a try.

Was also thinking that it might work for skirting under the house, would be easy to pack in around the posts and all the bracing.  I've got about three feet of open space under the house.  Would cob work to close that area in? I'm guessing I would need some kind of gravel filled trench for a footing under the cob.  ???

Yes - it could work quite well.  Have drainage routed around and away from the foundation.  Just a layer of rocks under the cob will be sufficient to stop moisture from wicking up into it. I use my Bobcat to mix my cob.  The squishing action of the tires is great for the right mix.  I do a yard or two at a time.

Here my clay has some aggregate so a 50/50 mix of sand and clay with a good amount of straw - maybe a flake or two torn up and scattered then well mixed  per yard is good.  You can cut bailed straw with a chain saw along the ropes to make shorter straws that mix better.  Squishing it well. with your toes or tires is necessary for it to work well -

http://www.weblife.org/cob/    Cob Builders Handbook - most of it online - thanks to Becky Bee.

Good stuff- http://www.knowledgehound.com/topics/green_building.htm
"Always work from the general to the specific." J. Raabe

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pagan

If the sun goes super nova... :)

glenn kangiser

Try it, you'll like it. [waiting]

With a bit of proper direction you can get the hippie gals to mud wrestle.... [cool]
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

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poppy

Quotehippie gals to mud wrestle....
I don't know Glenn; the hippie girls I remember didn't bathe or shave, but then again, they'd be covered in mud.  ;)

Beavers

Glenn,

Thanks for the info and the links.
Looks like I got some reading to do.  [cool]

RainDog

 Drat! All the hippie girls done moved to damn CALIFORNIA, and now I know why. Cob!

I think though, really, that my position can be illustrated like this:

Were I to come to this forum with thoughts on a NEW building material or method, of equally low dollar cost but with the same high labor intensity, having all the inherent problems of earthen structures, I think the idea would quickly be cut off at the knees as completely impractical and ultimately written off as unrealistic.

In my view, the attraction to cob as a building material is ultimately that it satisfies some romantic or ideological criterion for certain people. Folks may be yearning for a simpler time, a closer relationship to Mother Earth, a way to go against the grain of the sheeple's mainstream, or entertaining a romanticized view of primitive culture. Perhaps it satisfies their sense of artistic flair, adventurous spirit, individuality, need for attention from peers, or any combination of those and other personal abstract, metaphysical, and aesthetic motivations.

Not that there's anything wrong with that! If one likes the way it looks, or it satisfies them in some other way, no problem. I just can't help but notice the degree to which people are willing to bend over backwards, using all kinds of contortions of logic, to defend the building method's structural integrity. I doubt that some, say, plastic product with equal limitations would be defended so fervently.

We all have heartfelt loves that may defy practicality, but are still worthwhile to us on a personal level and that we should pursue to fruition. "I think it's cool" would serve perfectly well as a justification for using cob. If it's a matter of personal expression, then it becomes a matter of taste, and beyond reasonable criticism.

Anyway... blither blither. Someone's gonna bop me upside the head before long if I don't get off this thread. I can feel it in my bones. :D


NE OK


MountainDon

I like the cute factor of some of these cob buildings, same as I admire some of the cordwood buildings, stone buildings, real log buildings, straw bale and pumicecrete buildings I've seen. However, for me, they all involve too much labor effort or in some cases machinery to move components like logs.

It simply comes down to "different strokes for different folks", child of the sixties that I am.

As for earthquake resistance, wouldn't it be nice if someone built a test village someplace that's prone to 'quakes, with a nice selection of back to the earth and modern engineered techniques. Arranging to have a flood and a wildfire roll through would be nice tests too.
Just because something has been done and has not failed, doesn't mean it is good design.

Beavers

Quote from: RainDog on January 15, 2010, 03:27:55 PM
In my view, the attraction to cob as a building material is ultimately that it satisfies some romantic or ideological criterion for certain people. Folks may be yearning for a simpler time, a closer relationship to Mother Earth, a way to go against the grain of the sheeple's mainstream, or entertaining a romanticized view of primitive culture. Perhaps it satisfies their sense of artistic flair, adventurous spirit, individuality, need for attention from peers, or any combination of those and other personal abstract, metaphysical, and aesthetic motivations.


One of the cool things about this forum is that you get to see all the other folks who are building their own houses.  It seems like everyone is building their own house...but how many times do you get that weird look with the raised eyebrow from people in the real world, when you tell them you are building your own house?

It's easy for me to forget that building your own house is not a normal thing that the majority of people do.  A lot of people would say you are some kind of hippie, backwoods, nut job for doing so.   ;)

So yeah, cob or strawbales or any of that stuff isn't a "normal" thing, but neither are the things most of us here do.

I agree with you though Raindog that I don't think a cob house would be for me, but like I mentioned in an earlier post an outdoor cob oven would be great.  The materials cost is almost nothing, and my time isn't worth much more.  ;D  I could see trying a cob shed, or chicken coop, or stuff along those lines.

Just remember that the Jones' in the new subdivision in suburbia think that all of us here are freaks!  ;D ;)

RainDog

Quote from: Beavers on January 15, 2010, 05:09:34 PM

Just remember that the Jones' in the new subdivision in suburbia think that all of us here are freaks!  ;D ;)


We should go kick his butt for that.
NE OK

glenn kangiser

I like the bumper sticker.... "My kid can beat up your honor student".


One of the nicest things about living underground or possibly in a cob house is that people think that you are crazy and they are afraid to screw with you. [crz]

I like to enhance that perception by wearing a beat up Crocodile Dundee leather hat, growing a beard that sticks out in all directions, looking at them with one eye half shut and talking to animals, rocks and myself... [waiting]
"Always work from the general to the specific." J. Raabe

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glenn kangiser

Quote from: Beavers on January 15, 2010, 02:30:49 PM
Glenn,

Thanks for the info and the links.
Looks like I got some reading to do.  [cool]

Glad I could be of assistance.... :)
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

Please put your area in your sig line so we can assist with location specific answers.