Cob: Using Bricks[Marlin]

[lightearth at onebox.com]

[Kim]

"Hey Marlin. Thanks. Am I understanding you correctly? Are you saying I can use rubble all the way up to ground level and then start laying the rocks we've excavated? If so that is wonderful news. I thought I was going to have to have enough rocks for the underground part of the foundation also."

[Marlin]

The key as I see it, from experience, is that the rubble trench must be stable and well-drained. In cold country here (WI) with lots of possible freeze/thaw that means alot of small (1-3") gravel to the frost line with a drain pipe at the bottom draining out to daylight or a deep 'French well'. This comes up to almost grade (earth level) and is best if there is something on the outside (unfortunately we have resorted to styrofoam, recycled hopefully) to help insulate the drain/rubble trench and keep water/mud from washing into the 'drain'.

The 'river stone' type gravel won't break down like crushed limestone and is soo round and smooth that it seems like it would drain water well and not clog up as easily.

On top of this we have successfully laid broken concrete and stone, mortared together up  a foot or so and begun the cob or strawbale. The cob-like building techniques are nice cuz the top is supposed be very rough for adherence and leveling it is OUT.

Another trick we're going to try is to dig down at an angle away from the foundation to near the frostline and line this 'skirt' with clay to prevent water from reaching the rubble trench, which is the only thing I know that could cause stability problems.

See sketch below for first idea-simplest (using text not so good, I could draw you a better one and send you a Word file)

R= rubble/gravel
I= insulation
S= stone (both natural and broken concrete - Urbanite)
C = cob/cordwood/strawclay stuff
G= ground level (shown at the inside of the house envelope)
D= drain
m= mortar (could be lime/sand+'burnt clay' rather than portland cement)

(etc.)
 CCCCC
 CCCCC
 CCCCC
SSCSCS
mSSmSS
SSmSmS
ISSmSSGGGGGGGGGGGGGGGGGGGGG
IRRRRR
IRRRRR
IRRRRR
IRRRRR
IRRRRR
IRRRRR
IRDDRR


notice that I tapered the Cob wall in from the foundation a bit, you don't have to just wanted to show a drainage lip (we'd typically choose a stone there that slopes out and down for runoff)....remember BIG ROOF OVERHANGS make good earthen/straw walled houses! - keeps water directly off of wall and foundation!