[Cob] Urea as Binder in Cob

[Andrew Mebane]

<Will it be safe to build a dry wall foundation ?>

By "dry wall," Mahavir is referring to non-mortared stone or concrete
rubble. I am a stone mason, and I sometimes confuse people by using that
term since the more common definition of "drywall" is of course the interior
gypsum board. Unfortunately I've never been to India, so I can only offer
advice on what I know from building in the US.

I'm no expert on house foundations, but in planning my future home's
foundation, I have often contemplated how to make it solid and waterproof
without concrete or mortar. I have a gasoline saw with a diamond blade
called a "demolition saw" or a "cut-off saw." It has a 12" diamond blade on
it that cuts concrete easily and stone pretty well. Although I hate to
advocate more gasoline-powered tools, my advice is to use one of these saws
to cut recycled concrete chunks into tight-fitting pieces.

The problem with using stone is that it's usually very difficult to cheaply
obtain big enough stone that has flat sides. Of course you can fabricate the
stone with chisel and hammer, but if you're starting with mishapen
fieldstone, then it's going to require a lot of skill to fabricate the
stones into a sufficiently tight wall. Remember that many, many little
animals will love you for creating little spaces between the stones for them
to live in.

You can rent a demolition saw from many stone supply places, but of course
you'll need a respirator/dust mask, safety glasses, and ear plugs.

If you live in the United States, I recommend posting a "wanted" ad on
craigslist for broken concrete sidewalk/patio pieces. It would be best if
you can get pieces with two flat sides, and get the largest pieces that you
can move. Use a speed square to measure, then cut these into square blocks.
In building a recyled concrete dry wall, you're actually building two walls
side by side, with ocassional long pieces of concrete that tie the two
together. If your pieces are heavy enough that one person can barely move
one piece by him/herself, and you pay careful attention to leveling and a
tight fit, then I believe you can make a solid non-mortared foundation. Make
use of ramps, prybars, hand pulleys, and a team of strong people.