One of the most popular ways to create strawbale and cob homes is to use a post and beam structure. In this system large posts are used to support the massive amount of weight from the roof and distribute this load evenly on the foundation of the house. Many will be familiar with this technique, as load bearing houses--buildings that use the strength of the bale/cob walls to support the roof--are not building code and inspector friendly. Once again, the fact that load bearing structures do not comply with building codes has nothing to do with their structural capacities, but because these types of systems are unfamiliar. I suspect as our forests continue to disappear and our lumber industry continues to increase the cost for dimensional lumber, new codes will be created to accommodate smarter construction methods.
Of course there are a huge number of benefits from post and beam construction beyond code compliance. What we believe to be the greatest benefit of post and beam construction is that roof construction can immediately follow the building of the foundation. Both cob and straw are prone to moisture problems during the building phase. In our first cob house build we spent
|Cheap blue tarps work but only last 1 year|
At Spiritwood, the new house will mostly consist of load bearing walls with three large posts supporting a center beam that
The second benefit of post and beam construction is the amount of lumber and embodied energy the builder saves when compared to modern stick-frame construction. Remember that not only do modern stick-frame houses use much more wood to support the weight of the building, but the energy used to saw, plane and kiln dry construction grade lumber is substantial.
The last benefit of post and beam construction we will mention is also extremely important for the DIYer. Without a proper wood mill, making dimensional lumber is an almost impossible task, whereas cutting and peeling logs is a breeze compared and requires minimal skill with muscle-powered woodworking tools like an adze or a drawknife. You probably even have a tool laying around that will work well like our modified flat-nosed shovel debarker.
As always, remember to do an extreme amount of research and planning before starting any building process. For those interested in post and beam, check out James Mitchell’s The Craft of Modular Post & Beam as well as Rob Roy’s Earth-Sheltered Houses which gives great insight into the weight bearing capacities of timber framing under an earthen roof design.