[Cob] Hybrids, long

[kupononaturalbuilders]

I have built two hybrid structures.  While I don't have 100, 200 or 500 years of feedback I feel that they will structurally sound for many years to come.  The first structure was a small studio utilizing earth bags from Cal-Earth as the foundation.  We decided to follow their lead and stabilize our fill with a little cement ( we did test blocks and went with a 10:1 ratio).  We then built walls with normal cob.  We hammered in large stakes and built keys made from two foot long earth bags to help lock the cob to the foundation.  This worked very well and the walls were very stable.

The second structure is a cob strawbale hybrid.  We have sandwiched rice straw bales between an exterior and an interior wall of cob.  The exterior is about 4 to 2 inches thick while the interior is thicker, 4-6 inches.  As the cob dries and shrinks it squeezes the bales.  This combo allows for the best of both worlds: structural strength and insulation.  Then as you build benches or other things in the interior, you build with cob or other heavy materials that can act as your thermal mass.  This is insulated from the outside by your thick bales walls, resulting in slow heat loss or cold bank.  You could make adjustments as you deem necessary,ie.. post and beam structure, load bearing walls, cob columns to support roofing beams,etc...  My wife learned about this while she was apprenticing at Cob Cottage.  We were really happy with the building that we are finishing this year and are planning on building with this design again.

Also, with the type and number of your questions Jilly (and anyone new and considering building), I would strongly recommend taking a natural building workshop.  There are workshops being held all over the country, covering all aspects of natural building.  These workshops allow for hands on experience with the material as well as, if not more importantly, meeting with and networking with other builders.  It would be one the most important investments one could make in the entire building process. 

Jonathon