[Cob] Too late for cob this fall?

[Shannon Dealy]

On Sun, 11 Oct 2009, Rob Hoisington wrote:

[snip]
> project that my family and I are taking our time on, but I'm wondering if I
> should wait until next spring to begin the cob walls. Will it soon become
> too cold and wet for me to work slowly on the walls, or is it still possible
> to work through the fall, keeping it covered? I plan on building a curved,
> arch roof with old cedar shakes that I have access to. Thanks for any
> experience or insight you have.

When I have a project, I build with cob year round in Western, Oregon. 
Some general rules for building with cob when it's cold and wet:

  - Get some kind of cover over it to keep rain off but allow lots of air
    flow through.  Even with lots of air flow, a roof or tarp over the
    building area will keep the walls warmer.  While putting your final
    roof up is great, you may get better drying if your South facing roof
    is just a framework covered with a clear tarp or string reinforced
    plastic.  Using some kind of clear or translucent roof on the South
    side will allow sun into the building which will warm the walls a bit
    and provide moderate improvement in drying times.

  - Try to avoid applying cob to the wall if it is likely that the wall
    will freeze before the wall has achieved the equivalent of about one
    or two days of summer drying.  I realize this is a bit nebulous, but if
    the wall freezes with full water content in the cob it will puff up
    like pop corn and you will need to pull off that section of cob and
    apply again once it's warmer.

    NOTE: The issue is the wall freezing.  If the day time temperature is
    40 degrees and the over night low is going to drop to 32 degrees (or
    even a fair bit lower), it is unlikely the wall will freeze due to it's
    large thermal mass.

  - Determine which direction the winds generally come from at your
    building site and first start building the walls which would receive
    the least air flow once the structure is complete.  Your goal should be
    to maximize air flow through the building as much as possible
    throughout the building process.  The last wall or section of wall
    completed should be the one which blocks the most wind.

  - During colder/wetter periods, you may only be able to add cob to the
    wall once a week.

  - Cob can be mixed and stored wrapped in a waterproof tarp for later
    application if you find the walls are too wet to add additional cob.
    It doesn't matter if the wet stored cob freezes.

It will take some experience for you to apply the above, but cob is very 
forgiving, so just keep trying.

Shannon C. Dealy      |               DeaTech Research Inc.
dealy at deatech.com     |          - Custom Software Development -
Phone: (800) 467-5820 |          - Natural Building Instruction -
    or: (541) 929-4089 |                  www.deatech.com