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GSBN:Re: Fire test - earth plaster

Hi all,

Another point on earth plaster to bear in mind for fire testing (and I
suggest it would be great to use an earth plaster on at least one side of at
least one test) - 

There was a fire test done here (or possibly in Australia or elsewhere - I
can't remember) many years ago on mud bricks for fire rating them - they
were ordinary mud brick with straw in them.
The first thing that happened when they got hot was the surface straw burnt
off - thereby generating smoke, even thought the smoke stopped almost
immediately and the the brick went on to perform very well otherwise against
severe heat as would be expected.
However, officially the result  was a fail because of the smoke generation -
the same thing might happen with earth plaster if the outer layers at least
contain flammable material - depends on the test criteria.

Interestingly enough we sometimes apply earth plasters (often containing
paper pulp as well) as a thin finish over gypsum board walls - a colleague
had done this to a caf? that burnt down, and the firemen were very impressed
at the extra fire resistance given to the gypsum board walls by the earth

I do see some danger for earth plasters if they are to be subjected to high
pressure hosing - unless the fire first gets the surface up to red hot
temperatures (around 800 deg Celsius) and there is a lot of fire resistant
aggregate in the plasters - then it would be like well grogged raku pottery
clay that gets fired to red heat and them dunked in water, and survives

And Bruce - at least graffitied PVC siding will burn well for the


Graeme North Architects,
49 Matthew Road,
RD1, Warkworth,
New Zealand 1241
Ph/fax +64 (0)9  4259305


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