[Cob] Urea as Binder in Cob

[Mahavir Mahedu]

Hi everybody,

I am planning to build a cob house with thatched roof in India.

I read in the literature by Laurie Baker that Urea acts as a very good binder for cob and earthen plaster. For this reason, animal urine is being used for centuries in the cob mix. Pig's urine has the highest urea content and hence is considered to be the best.

Anybody has any experience on this topic ?

1. Would adding urea to the water used for cob be good ?

Also, cow dung or horse shit was used in the cob mix for the lignin content, apart from the finely divided fiber. The lignin is supposed to act as plasticizer ( so that less water is required and yet the cob is workable; and less water means less shrinkage during drying).

2. Would it be advisable to use ligno sulphonate plasticiser ( used in modern concrete construction) ? is it a natural , degradable  and non-toxic material ?

The area in which I intend to build the cob house in lies in seismic zone 4. 
 
3. Will it be safe to build a dry wall foundation ?

Mahavir.


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