How to Make Cob Bricks Out of Household Items

Gather your materials. You will need sand, clay and straw, raw materials typically found around a home garden area.

Lay down a tarp on your lawn. Place a few handfuls of clay, straw and sand on the tarp -- enough so that you can form a single brick that is 2.5 inches tall, 4 inches deep and 8 inches long. The proportions of sand, clay and straw will depend somewhat on the properties of your clay, so you'll need to experiment with this. It is unlikely that the clay on your property is pure clay. The amount of clay and soil will vary from location to location, so the actual proportions you use in each brick will vary as well. Note the approximate proportions of the mixture then slowly add water until it starts to stick together.

Mash the mixture by hand, kneading it like dough. As it starts to get more difficult to work with by hand, step on it with your bare feet.

Form the mixture into a brick by patting the sides with a board and flattening them out into a rectangular shape. Set the brick aside to dry. If possible, set it in the sun to speed up the drying time.

Repeat Steps 2 through 4 with a different proportion of straw, sand and clay. You're trying to find the right recipe for bricks given the materials on hand. The cob material should hold its shape, not crack or fall apart when you mold it into a brick and should not pull apart. You can wait for the first brick to dry, before forming the next brick, to see how well your first recipe turns out.

Make several test bricks from different recipes.

Examine your dry cob bricks. The bricks with the largest or most cracks are those that have too much clay in them. Grainy bricks that shed sand when you lift or rub them together have too much sand. Test the brick strength by dropping each one. The brick recipe that produces the strongest brick with the fewest cracks is the one you should use for the rest of your bricks.