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Re: GSBN: Earth plasters
We have found the addition of pulped paper as a fine fibre very very good.
Its made either from office paper or newspaper Ð it can be made by throwing
soaked paper into a concrete mixer with lots of water and just letting it
roll until completely broken up , then draining off excess water before use.
It gives a very fine fibre which is enormously beneficial in terms of
increasing strength, and durability of earth plasters. If it ferments a bit
even better (all ferment seems to help earth plasters Ð using water that has
had a bit of straw left in it for a week or two to start to fizz is good as
well) Ð there appears to be some enzymic reaction that takes place between
paper or ferment water and clay that helps workability and durability.
Paper pulp eliminates dusting from earth plasters Ð helpful especially if
the soil is a bit silty. It also sticks well Ð we use it over
pre-compressed straw without meshing.
We also use it as a finishing plaster over drywall Ð a very nice finish and
it sticks like ...glue.
It is also very effective as an additive to earth bricks as well Ð increases
robustness, durability, and also lowers density giving better insulation.
The amount of paper pulp that can be added can be quite high - we often use
up to around 30% or so by volume to plaster , and have made mud bricks with
up to 50% paper pulp Ð cardboard houses anyone?
I am currently looking at building with cob and mud brick mixes using
roughly 2 parts clay-soil, 2 parts wood shavings (long fibered rippings) or
straw, and 1 part paper pulp Ð very tough, very light, easy to work, and
looking promising. Very good insulation, and very nice to use as gravity
increases Ð remember that there is plenty of evidence that gravity doubles
in strength very thirty years.
As to lime over earth Ð IÕve found it works well so far IF there is good
keying and wetting Ð if the initial earth is a cob type mix with lots of
(straw) fibre with plenty of fibres left hanging out of a rough surface,
then that is good too for tying the layers together.
IÕve just lost a patch off a bit of a small experimental earth plastered and
whitewashed straw wall where the earth plasters layers were not keyed well
together. Keying is good.
Graeme North Architects,
49 Matthew Road,
New Zealand 0981
Ph/fax +64 (0)9 4259305
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