Go to Bumpy Road of an Unconventional Christian
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- Go to A Cob Church
Thanks Sannhet,
You have described the process well.
posted by
Make2short
on March 31, 2006 at 8:36 PM
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Make2 -
We have yet to start construction, but I can tell you briefly what I have learned so far. Straw bale is one of the best materials to use in building any kind of structure. It resists pests and is fireproof (because the bales are so tightly constructed, there is not enough air in the typical bale to support fire). A typical straw bale is rated at R48 (insulation properties) without plastering. A typical home with wood framing and installed insulation has an R-factor of 19.
The process is fairly simple. Once a foundation is pored, pieces of rebar are inserted every 18" or so around the perimeter of the foundation. This will hold the first course of bales in place. As each course is added, a piece of rebar is inserted through the top bale and into the bottom bale to improve the solidity of the structure. You can build a structure entirely out of bales (meaning that load-supporting walls are bales as well as interior walls), or use a post-beam approach, where a frame is built for the structure and bales are inserted between the frames. Doing it this way will increase the cost, but for some it offers more peace of mind than total bale construction, though there are no studies that I have found that show post-beam is stronger than all-bale construction. Using plaster on the interior and exterior of the bale walls helps to support the load of the roof, so all-bale construction is safe and will bear any weight, including a second floor (though there are a couple of things you would want to do prior to putting up a second floor).
The biggest concern for straw bale is moisture. Typically, you would put down a layer of tar on the footer of the foundation prior to laying down the first course of straw, to insure that the cement does not outgas moisture, which it tends to do. And then you must make sure that your walls are covered each time you quit working on the structure, to protect them from rain. Another concern is making sure that your city/county/state will allow construction with non-standard materials. Some states and counties don't allow it. Luckily, in Arizona most counties allow it.
The great thing about straw bale construction is that it is inexpensive (around $10-15 per square foot - providing you do the labor) and very easy to use. You can cut bales to fit into specific spaces and to create unusual interior or exterior walls. They aren't extremely heavy and can be moved into position with just one person. When we begin construction on our home, we plan to have the entire structure up with the roof on in a week end (just over two thousand square feet). We also plan on starting with a garage with a loft, so we can get the bugs worked out before we start on our home.
If you have any other questions, please feel free to email me. I've got lots of resources I can share.
posted by
sannhet
on March 31, 2006 at 7:58 AM
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Tell me about your house, Sannhet
posted by
Make2short
on March 30, 2006 at 4:49 PM
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Make2 -
We're building a home out of straw bale, so I think Cob is a great idea!
posted by
sannhet
on March 30, 2006 at 11:17 AM
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