Cob House

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Cob House

Postby oil » Mon Jul 28, 2014 2:30 pm

this was the closest where i thought it could fit in,

so i am wondering whats your opinion on this one is:

as far my reasearch did go it seems that cob has a shitload of advantages over other building materials espacially in humid climates

there is a huge article in german language, Translated into EN -
Original German Language Link -

Basically the article is saying that / Clay / Cob is the ideal Building Material for the Tropics
in Short

Clay is not a standardized building material, ie he will ever tested by locality different characteristics and must be individualized for its suitability and necessary accessories and assessed
Clay shrinks as it dries out (at Nasslehmverfahren 3-12%, with rammed earth 0.4 to 2%): this dry and shrinkage cracks can occur
Clay is not waterproof: it must - be protected especially when wet -before rain and frost

Clay regulates humidity: clay bricks can absorb 30 times in two days as much moisture as burnt bricks, when the relative humidity of the room air of 50% increases to 80%. Even at 6 months long 95% humidity dried mud bricks are not soft
Clay retains heat
Clay saves energy and reduces the pollution: it needs only about 1% of the energy necessary for the production of the fired brick or reinforced concrete
Clay is indefinitely reusable: you can reduce it at any time and re-edit with water
Clay building materials and saves transport costs: it is available almost everywhere and often falls eg on the excavation of pits
Clay is suitable for self-
Clay preserved wood: wood and other organic materials, which are surrounded by clay are dehumidified and kept dry. Thus it prevents fungal and insect attack (with straw, however, the preservative effect of clay does not suffice)
Clay binds pollutants such as sulfur and phosphates
Clay shields radio frequency radiation

so i am just wondering if anybody else considered building his house with Cob here in thailand
after i ve seen the video above from this guy in the UK i am have to admit i am quite impressed with whats doable with it, never really thought that cob would be that strong
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Joined: Thu Apr 17, 2014 2:03 pm
Location: Chiang Mai,

Re: Cob House

Postby canopy » Tue Jul 29, 2014 8:04 am

Clay shrinks as it dries out...and shrinkage cracks can occur

Surprised to see this listed as a disadvantage. This attribute of clay is precisely why cob has sand mixed in to a quantity such that all the sand particles interlock and so when the clay shrinks, the sand doesn't and there are no cracks. So the statement should be preceded by "If your mix is wrong, then..."

Clay retains heat

Major red flag, this isn't the SW United States with hot days and cold nights. In Thailand's climate days are hot and evenings are warm. A clay wall is a gigantic thermal mass that will absorb heat in the day and reflect it into the structure in the evening known as the fly wheel effect. But you don't want to add massive heat in your house at night. This is why these days you see a lot of people build with AAC blocks rather than more traditional red bricks.

Heavy clay walls like cob and adobe are the worst match for Thailand's climate. It doesn't mean you can't use them, just know that the comfort level will be way down. It might be wise to select a different "green" wall system that better facilitates comfort.

And by the way, another great advantage of cob I did not see listed there is the walls are load bearing.
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Joined: Sun Aug 16, 2009 1:15 pm

Re: Cob House

Postby canopy » Tue Jul 29, 2014 12:34 pm

Very enlightening video. Speaking for myself I started with fascination and ended with heart sinking. The guy was no newbie and very experienced with cob. Yet cob added years to the building time even with heavy machinery and lots of workers. The cob walls did not provide the desired insulative value and so it was completely covered with high r-value modern material panels on the outside! Cob added such a high unexpected cost to the project and they ran out of money and halted construction. Did they finish it? The cob in this case did not seem to have any functional value or be cheap or easy. Feel sorry for the guy.
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Joined: Sun Aug 16, 2009 1:15 pm

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