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When designing my cob house, it was an important goal to keep my building costs very low and to obtain as many building materials as locally as possible. Natural materials were my first priority, and recycled building supplies were preferred over new materials. Few materials were purchased new, and about as few are synthetic.

In this very detailed entry, Recipe for Building a Cob House, you can learn what it took to build my cob house for about $3000 in material costs. You’ll also learn exactly how much cob I made (all by foot!), and specific amounts of material that went into the construction.

Cob House Timeline

I started digging a foundation on April 19, 2008, and moved into Gobcobatron on July 11, 2009. I effectively worked from April to November of 2008, and then April to June of 2009. In total, I estimate that I spent nine months working on my house, full time. I spent every possible day that I could working, except for when it was raining or when I was traveling.

I literally worked every day per week full time, usually with one other person. I have no hour count, but you could imagine it’s very high.

Batches of Cob in the Building

I stomped 219 batches of cob* for the walls by foot, with the help of over 75 work exchangers, visitors, and friends throughout the year. The cob bed and bench took nearly 20 more batches of cob, almost 1/10 of the material it took to build the house itself!

*one batch of cob is equal to three 5 gallon buckets of sand, and 2.5 worth of clay, nearly 30 gallons of material.

Cob House Cost Breakdown

I’ve kept close records of the costs of my building materials, and have determined that I have spent less than $3000 on building materials for the cob house. (I spent another $1000 on labor.) Here’s what I actually bought, and what I paid for my building supplies:

• sand (just over 30 tons total) – $507
• gravel (about 13 tons total) – $177
• straw (16 bales) – $36 (most straw I used was free)
• black walnut scrap lumber – $100
• misc. lumber – $20
• windows – $220 (two casement, one double hung window)
• electrical – $28
• galvanized wire – $30
• nails – $100
• raw linseed oil (for floor) – $72
• EPDM pond liner $622
• polycarbonate for skylight $400

and for the rocket stove:

• firebricks – $70
• flue pipe – $228

The two most expensive individual items are in bold. (Perhaps not surprising is that they are both part of the roof.) As you might imagine, many things are not listed because they were obtained for free – clay for cob, roof rafters, (hand harvested from our land and neighbor’s land), my large south window, urbanite for the foundation, etc. This is a very inexpensive house.

UPATE and an IMPORTANT NOTE: This house, as you might be able to tell, does not include a kitchen or bathroom. Basically, it’s a bedroom for one to two people at best. When I built this house, I had access to kitchen and bathroom facilities elsewhere. You can imagine that the cost of building would be much higher with those features…

The total cost of supplies for the house is $3000. If I included labor costs, the house cost $4000.

Recipe for Building a Cob House

With $3000 for supplies, $1000 for labor, and nine months of my own full time labor, I was able to build Gobcobatron, a small cob house with interior dimensions of roughly 15’x13′, and a footprint of (again, roughly) 20’x18′. Practically all of the labor was completed by hand (and foot), including making and applying all of the cob.

It’s true… you can build your own home with little money, but with lots and lots of time and enthusiasm. Even a small building is a big endeavor. And again, this is NOT your typical house, so please be aware of that fact as well! It’s basically a glorified bedroom, with no electricity or running water. This is about as bare bones as it gets. This house would not serve the full time needs of most people without access to amenities and facilities in another structure.

Cob Houses in Cold Climates: Important Note

Update…

As it turned out, Gobcobatron proved to be a 3 season dwelling at best. Because the house has little to no insulation, it is not appropriately designed for the cold northeast Missouri winters. This house design is much better suited to extremely mild climates, including parts of the southwestern US.

I stress this fact to everyone I have contact with who is interested in building with cob. Please read this for the full story of my experiences living in a cob house in a cold climate. I heartily DO NOT recommend this. There are much better natural building solutions (including straw bale) for cold climates. Well hey, I guess the experience wasn’t for naught — I’ve been able to educate a lot of uninformed individuals about the importance of insulation, and the fundamental differences between thermal mass and insulation as a result of my personal experiences.

There ya go!

Gobcobatron Construction Slideshow