Cob Gustave Stickly walls

[John Stephenson]

For some time I have been seeing emails on this list from novice 
builders asking about the insulation values of cob, and seeing the more 
experienced cobbers responding that cob doesn't insulate but instead has 
thermal mass.  I believe that there is a way to have insulation built 
into cob walls.  
	About 1912, Gustav Stickley wrote an essay on economical concrete 
construction.  What Mr. Stickley noted was that he was not satisfied 
with the way monolithic concrete walls held cold and moisture, and the 
resulting effect those two elements had on interior decorations i.e. 
paint and wall paper.  What Mr. Stickley suggested was introducing an 
insulative air gap in the wall separating the inside from the outside 
walls.  He realized that the common way of doing this required expensive 
forms and created thinner weaker walls so he devised a method to 
eliminate these two issues.   A more detailed description of this 
process can be found in the book "More Craftsman Homes" printed by Dover 
ISBN: 0-486-24252-8. 
	 What Mr. Stickley proposes is the use of wooden forms that can be 
constructed on site by the builder.  Each form consists of matched 
sheathing boards 7/8" thick (boards used for the exterior covering of 
houses that have a tongue and grove edge) and 5.5" wide.  Three of these 
are fitted together to make each side of the form, this will create a 
16.5" high form allowing you to create your wall in approx. 16" lifts.  
The three boards are fastened together at 24" intervals with vertical 
wooden cleats.  The insulating air space is created by a third set of 
wooden forms.  This form is made from the same sheathing boards the 
others are made from, however this third set stays in the wall.  Mr. 
Stickley devised a metal reinforcing tie that is held in place by the 
center form while the wall is poured/packed.  Once the wall is dry the 
ties bind the inner and outer walls together strengthening them.  

Prior to fitting the three parts of the form together the center boards 
need to be soaked in water over night in order to have them swell as 
much as possible.  After the wall is constructed the center board will 
eventually dry out and shrink leaving an insulating air gap between the 
inner and outer walls.  
 
This is only a cursory description of the process and probably confusing 
so I recommend finding the original essay and studying it since it has 
many illustrations to help visualize the process.  Also note that this 
process was also intended for concrete walls I am not sure if it will 
work the same with cob, but I can not imagine why it wouldn't.

Your comments on this are welcome.

John


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