There is a misconception that natural building is inherently cheaper than conventional construction. We have probably contributed to this idea by building a cob house for $7,000. While this is not a record for cheapness it comes out to about $25/square foot and that is one-fourth the cheapest contractor rate I know in this area.
The reason our house cost so little is not because the walls are made of clay, sand and straw. It is because, first of all, there was no paid labor. Lin and I were helped by many generous volunteers. Secondly, the house is only 14×18′. Subtracting for the wide walls and adding the space in the loft we have about 300 sq’. The national average is over 800 sq’ per person! This cozy space works for us because we are outside as much as possible. Lin likes to say that her favorite thing about our house is the ceiling and she points to the sky. Finally, our house is cheap because it has almost no systems. A free woodstove, a sink made from a popcorn bowl, and a two burner stove we stole from the camper do not add up to much.
All the most popular natural building systems are really just wall systems. In conventional building the walls, including inner and outer covering, are less than 15% of the total cost of construction. Even if your walls were free you would not save more than 15%. And if you did cob or strawbale with paid labor you would probably spend more than conventional construction. Natural building tends to be much more labor intensive than conventional. Stud walls were created as the fastest way to build and as far as I know they still hold that distinction.