I settled on cob as a material of construction after eliminating other options one by one. When i considered cost, embodied energy, ease of use, comfort for occupants, aesthetic potential and sense of fulfillment I found cob was hard to beat. And now having grown familiar with it, I will stay with it for long, long time, I think.
My first pick was compressed earth block. I went over to Auroville and studied the process for a day. It was too demanding and needed a team of six, needed cement and produced far too many blocks. I decided it was for good sized communities that wanted to use their own labour to build a number of homes.
Would rammed earth be easier? Sure soil preparation is less fastidious and no machinery is required as with earth block machines. But it needs form work, scaffolding and a team of at least 3 sturdy workers. At pointReturn labour is hard to by.
There was of course the option of the ‘instant’ variety of building using cement, sand and steel, all bought and brought in. I had built the very first structure, the strongRoom using these. The frustrating delays with workmen defeated any advantage this method had. The escalating prices of materials, nailed the idea dead. There was in addition, the nagging guilt about the environmental cost of this option.
And so I came to look at mud. At pointReturn the soil is caked hard, a result of most top soil having been washed away by rains and absence of organic matter. After rains, the earth hardens within hours of sunshine; a crowbar directed at it bounces back like it hit a rock. This told me that it would be a good material to build walls with.
An hour of Internet research on cob building quickened me. I ordered Ianto Evans classic ‘The Hand Sculpted House’ the same day. This is a classic. Not only does it teach all you need to know about cob building, it also makes you look afresh at how dwellings should be designed.
Cob is the simplest, most abundant and most used building material on this earth; it is earth itself. As long as there is a reasonable proportion of sand and clay, it will serve. You add some reinforcement like straw, add water, knead it underfoot and it is ready for building. You take palmful of the stuff and just pile it up. There are some limitations but none that upsets its high rank.