[Cob] Marlin's rubble trench

[Amanda Peck]

Around here, I've been told that the ideal for a rubble trench is the 1" -2" 
crushed limestone.  Not the bigger (although some mixed in with that seems 
to pack down nicely), not the "crusher run" or "fines" or "roadbase," which 
can pack down into something that will retain water.  My informants say that 
the crushed stuff bonds to the surrounding soil better.  No information on 
whether that is true.

by the way---

Footing--in modern building, something on the order of a nice pad of 
generally reinforced concrete rougly 2x the width of the next layer 
up--sometimes a little less than that if you have wide, light walls, e.g., 
straw bale.

Foundation--heavy duty pier or continuous layer--holds up the walls.  If 
it's continuous it can also form the basement walls--needs to be waterproof. 
  Modern practice is not to vent a continuous foundation but to provide 
drainage outside of it.  Rubble trench--e.g., Marlin's river rock, or the 
local here crushed rock does have masonry of one kind or another, stone or 
urbanite for the most part from ground level--or just below, on up.  Needs 
to be the width of the base of the walls.  May or may not be reinforced.  
Depending on who you are, you may or may not feel the need of a bond beam 
above that (yes, generally, with straw bale, but you'd be hard pressed to do 
that with some of the stemwalls for cob houses)
.....................

Marlin wrote:
We used 'river stone' or washed stone - 1 , 1 1/2
inches usually...it's actually from glacial drop
around here.