Hello all,

Been a creeper on here for some time but finally registered and this is my first post.

I recently bought a house with a few acres in Jamul, California. The lot is this decomposed granite and I am wondering if this stuff would be any good in a cob/adobe mix? If not what uses might it have for building purposes? I guess earthbags would be an idea but I like the cob better. If I cannot find a good clay source on the property where in SoCal is a good place to get clay?

Seth

Decomposed Granite is used extensively as a road base material prior to paving because it compacts really well. I would say that it would be excellent material for Earth Bags!

Also, where in Jamul are you? I am out in Deerhorn Valley.

It can be used for COB or anything you want. There should be some clay in it, do a jar and block test. If not add a natural polymer like lime, if that is not enough add some portland cement too or fly or wood ash. Rammed Earth take to it well I bet. I'd have a passive radon mitigation and be active ready.

I'm in San Diego when I'm not on the road working

I'm at the end of Lawson Valley where the pavement ends.

I am building a cob house up in Ramona and getting clay from the land. I have seen people getting rid of soil from their property on craigslist and some of it looks to have decent clay content. You could try posting a want ad on there too.

Bringing this thread back from the dead. As a coincidence, I happen the be the third on this thread from Jamul. We have lots of decomposed granite here and my questions is would I need to mix it with anything other than 10% portland for a strong rammed earth wall. Would it need clay or sand? This seems like great material and I have a free unlimited supply.