Cob: Window Installation

[Shannon C. Dealy]

On Mon, 6 Jan 2003, Darel Henman wrote:

[snip]
> I have a question regarding the statement below about replacing a pane.
> You describe carving out the dried cob, putting in the new glass pane
> and then using new cob over the old.   I should think that some kind of
> preparations, such as a.) damping the underlying dry cob first before
> applying the new, or b.) somehow prepare the surface so that new cob can
> be keyed in for a better meld with the old.  Do you have any advice on
> this.
[snip]

I ignored this because there are standard techiques for applying new cob
to old cob, but of course, many may not be aware of them, so:

  1 - Provide a means for the new cob to mechanically interlock with the
      surface of the old cob.  This can include hammering old bent nails
      or driving wood screws into the surface of the old cob, or drilling
      holes in the cob (I like 1"+ diameter holes drilled with a masonary
      bit).  Any other technique you can think of that will provide a
      reasonable mechanical bond will probably do as well.

  2 - Before adding new cob to old, dried cob, thoroughly wet the old cob.
      Usually this will involve repeatedly soaking the old cob with water,
      the more water you can get the old cob to absorb, the better it will
      bond with the new cob.  Generally, you will not be able to get the
      old cob to soften.  For cosmetic repairs, plasters, and
      non-structural work (such as what I propose to do with embedded
      glass), I usually repeatedly wet the surface over a 15 to 30 minute
      period (for a completely dry wall), for a major repair (adding a new
      section of wall) where I need a really good bond, I might repeatedly
      soak the area as often as possible (everytime I walk by) for a few
      days.  What is best for your situation (particularly for major
      repairs), could vary a great deal depending on your particular cob
      mix.  On my zero dollar house (which uses a really crappy high
      clay/silt, low sand mix - the local soil with no supplements), I can
      actually get the surface of the cob to soften in less than two
      hours, which you will normally not be able to do with a good cob
      mix.

  3 - Add the new cob, preferably a mix that is fairly close to the
      original if possible.

Shannon C. Dealy      |               DeaTech Research Inc.
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