Cob: Cob failure problems

[Shannon C. Dealy]

On Thu, 29 Aug 2002, Laura Guldin wrote:

> Hi,
> A friend of mine was very disturbed by the toxicity of
> linseed oil. It really smelled.
> Nobody else is talking about this.
> Is hemp oil better? Or what else.

I would venture to guess that the problem your friend had was not with the
linseed oil, but with the thinners used in it.  There are some thinners
which are far less toxic than others, though I am not sure what is
available as far as commercial preparations of linseed oil with thinner in
it.

NOTE: Pure linseed oil is edible, many people use it in salads, etc., and
it is available at your local health food store, though in this form it is
probably not suitable for making floors.

> Also, the floor is pretty soft. When you drop a heavy
> object, it makes an impression on the floor. Things
> don't break, that's the good part.
> Any ideas for hardening the floor beyond beeswax

Done properly, it shouldn't dent unless you drop something pretty
serious (which would dent any other floor as well), it should be able to
take high heels, piano's, etc. without damage.  Some things that make a
difference include:

1 - Prep work, was the earth and gravel below the floor thoroughly
    compacted before starting the floor.

2 - Is the floor thick enough?  It is normally done in several layers,
    if it's not thick enough it is likely to have more problems handling
    point loads and impacts.

3 - Your cob mixes for the top layers should be a very high sand mix, sand
    is pretty incompressible and makes it much more resistant to point
    loads and impacts.

4 - Linseed oil treatments, it takes many coatings of linseed oil, mixed
    with progressively greater amounts of thinner, and it needs time to
    dry/harden.  So far as I know, the beeswax doesn't help with
    hardening, it just provides a final seal/finish once the linseed oil
    has dried.

It's been several years since I last worked on a floor, maybe someone else
on the list has more recent information or a better memory.

Shannon C. Dealy      |               DeaTech Research Inc.
dealy at deatech.com     |          - Custom Software Development -
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