How to Build a Cob Home

One of the oldest methods of building low-cost homes is through a material known as cob. Cob homes have a good deal in common with adobes or rammed-earth homes, as the principal construction materials are all organic and environmentally friendly. Cob is made from a mixture of clay, sand and straw and can be used to build homes one handful at a time. In addition to the lower construction costs, cob homes can provide a reasonable amount of all-natural insulation.

Difficulty: Moderately Challenging

Instructions

Things You'll Need:

• Rocks
• Gravel
• Rubble

1. Pick a site on which to construct your cob home. Consider elements like natural shade and window positioning to reduce your need for heating and air conditioning. Pick a site that offers natural storm drainage.

2. Decide on the size, design and features for your new cob home. While a cob home doesn't require blueprints as detailed as a normal home, you'll want to have a firm idea of how many rooms you'll need and how you plan to connect them.

3. Reject the notion that all walls must be straight and all corners must be right. One of the unique structural features of most cob homes is rounded walls. By building rounded rooms, you'll speed up the construction process, save money on building materials and provide greater structural integrity.

4. Build a solid foundation for your cob home's walls. Dig a trench along areas in which you plan to build walls. Stack rocks, gravel and rubble at a depth of several feet, so that you can build your cob walls atop a sturdy base.

5. Leave the foundation's surface jagged. A smooth or sloping rock surface will allow the cob to slide free.

6. Create test bricks with your cob. Look for cracks in a brick's surface, as this can be an indication that the cob has too much clay in it. Leave the brick edges rough, so they have plenty of opportunities to mold against each other.

7. Build your home's walls with quality cob bricks. Stagger the bricks to make sure their edges don't form neat lines.

8. Finish your cob home by adding a roof and floor.

9. Install plumbing and electrical systems with the help of a reliable contractor.

Tips & Warnings

• While cob homes are easy and cheap to build, your city or neighborhood association might have specific laws that prevent homes from being built with all-natural materials. Make sure to check with your local building inspector before you begin construction on a cob home.
• Cob home purists will tell you that the best way to mix cob ingredients is by stomping them with bare feet. Save time by using modern machinery.
• While cob homes offer more natural insulation than their adobe counterparts, you may want to supplement cob walls by adding cellular-fiber insulation. It's inexpensive, easy to install and completely organic.

[moonsinger74]

on 4/23/2009 How does it dry or set or whatever. What I mean is when you're done building a wall or whatever do the contents of the wall stay in a semi-liquid state (muddy) or does it dry over time or are you the builder supposed to do something about it?