Cob Building

Cob Oven in Afrikatown, Oakland

The first time I heard about cob building was when Liter of Light pioneer, social entrepreneur Illac Diaz introduced dome-shaped mud houses in the Philippines. In 2005,  he built a prototype in Escalante in Negros Occidental, very-well embraced by the media because it really was a promising innovative solution to the country’s housing problem.

In 2013, there’s a Mud House Building Project initiated by Kaila Ledesma Trebol. With the community, they have managed to build six mud houses, including a chapel, as “commissioned by various organizations in Negros in partnership with the Philippine Reef and Rainforest Conservation Foundation Inc.”

Just to be clear, mud ‘structures’ are not solely mud but mud mixed with other nature-base finds. Personally, I have not done any mud building projects. My husband, however, has one when he built a cob oven with his Permaculture classmates about a month ago, which I got to finally see last Sunday.

The cob oven they built is right at the Permaculture Garden in Afrikatown in Oakland. I’m sure you know what an oven is, but a cob — what exactly is a cob? A cob is a mixture of sand, clay, water, and straw and is used to create things as small as an oven to as big as a house. It’s an almost all-natural way to build structures except you have to realize that being “natural”, it has its limitations. For one, a cob structure will not hold firm with prolonged exposed to moisture, so it would require a sealant, and touch-ups every so often.

In any mud structure, the clay binds, the sand provides compaction strength, and the straw gives it tensile strength.


So how do you make a cob ‘masterpiece’?


Cob building community project (Photo credit: Brian Hicks)

Of course you have to make sure you have all the materials. For the cob oven the class built in Afrikatown, they used sand, clay, straw, water, bricks, wood, rocks, and bottles.

First they did is to come up with the mixture — clay, soil, straw + water. After building a solid base using rocks (providing the shape of the structure), they just covered it up with the mixture. For the main oven, they also added bottles as fillers. For the seats, again, the mixture.

Basically, it’s the same as doing construction work but instead of hollow blocks, cement, and steel, you use natural alternatives like soil and straw (or recycled, like the bottles). After drying it out completely, you may start putting your artistic flare on it by painting over it, and then you can seal it with linseed oil. Sealing is extremely important because it would make your ‘masterpiece’ more sturdy and resistant to weather changes.

Cob building is a great community project (Photo credit: Brian Hicks)

I feel that building cob structures has a lot of potential in the Philippines because we have an abundance of the natural materials needed for construction. I could imagine an eco-park with benches made with cob, and playgrounds too, instead of steel. I could also imagine backyards with this.

If you want to be updated on mud house building projects in the Philippines, check out this Mud House Building Community. If you are in San Francisco Bay Area, CA, check out Urban Permaculture Institute.


Have you built anything from clay? Share your experience below!


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