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Re: GSBN:Exterior cladding question
What I can tell, from my own observation and experience, both in France
and in Morocco,
is that earth, once dried, has an enormous capacity to deal Slowly (but
surely) with moisture in buildings.
Even with very thick walls (in Southern Morocco, good old Kasbah walls
are often 80 cm thick or more (that's about 30 inches at least) never heard
of moisture problems. Well, you could say it may be because Morocco is
like Arizona: very hot, very dry, So moisture never matters...
But in France there are quiet a lot of old farms, houses, and even
Chateaux, built with mud bricks or rammed earth or cob.
Not only in the south; in wet and cold areas too; in winter, it was wet
outside, all the people breathing inside, plus the cattle in old times, and
it just did it; these houses lasted hundreds of years and many still exist
When I was building in Morocco, often with mud bricks, I was amazed how
fast mud gets dry.
When a brick came out of its mould, it looked like thick yogurt almost,
you could get easily a finger right through, effortless. After a day, you
could lift the brick, it wouldn't break easily. After 3 days you could
use it (even though I had them standing a whole week for total safety).
Each piece was 13 X 6 X 4 inches.
We could say, definitely, that earth is always "in a hurry" to loose any
enclosed water . It is absolute breathability.
Earth is the best friend of straw because it will drive away all presence
In your Halliburton project, I am 100% confident you can proceed as you
describe, no fear: connect fully the bales to the brick wall.
There wont be condensation , because mud , especially if mixed with some
chopped straw (for the contact mud mortar) is not cold and shiny, but warm
and micro porous, doesn't condensate the tiny water drops of vapour. It
allows it inside via its porous surface.
You could probably get a condensing. point if the clay carried a lot of
sand (witch may get colder, and has a "locked" surface, non absorbing.
Or by polishing, pressing in, the clay surface, like when building an
earth floor: then water is stopped at the surface because everything was
done to stop it.
This doesn't happen with mud bricks, or cob : compression is not
All mud aren't identical: depending on microscopical structure diversity,
some being more breathable than others.
Testing their qualities before choosing an earth for bricks or cob is
Does Ontario have earthquakes? Because an other advantage of full
contact between bales and the wall is extra solidity
added: the bales will reinforce structurally the wall they stick to.
----- Original Message -----
From: "Chris Magwood" cmagwood@...
To: "GSBN" GSBN@...
Sent: Monday, February 07, 2005 4:38 AM
Subject: GSBN:Exterior cladding question
I'm in the midst of designing a building for the Town of Haliburton,
Ontario, which will provide a new space for a charitable group in which
they will run their food bank and thrift store operations. It's a great
project, as the building has an honourable end use and will be located
right in the centre of the town, next to the art gallery and a park.
They are also keen to make it as sustainable as possible.
One of the requests of the town council is that the building be
designed to "fit in" with the existing local architecture. The art
gallery used to be a train station, so it's a nice building to echo.
But part of fitting in in this part of Ontario is a having a brick
finish. I've done some brick and stone facades in front of bale walls
before, but I'd rather not do them again.
One option I'm looking at is the use of compressed earth bricks. I had
a chance to see them being produced and even to lay some up during the
ISBBC in Denmark this summer. A local builder has recently purchased
one of these machines, and I've already decided to use them in the
I don't have any doubt that the earth bricks can be used as an exterior
cladding. What I'm wondering is this: If I lay up the bricks as an
exterior load-bearing wall, can I stack the bales directly against this
wall? I'm a convert of the Tom Rijven school of dipping bales in clay
slip, so I would dip the back side of the bale and press it against the
earth bricks, then give the interior the usual coat of earth plaster.
The issue is permeability. Obviously, the compressed earth bricks are
going to be less permeable than the plaster, based on the thickness (10
inches) and the density. But do you think this will be problematic?
Will the earth bricks be capable of taking up migrating moisture and
letting it go to the outside at a reasonable rate? I'm pretty good at
detailing a bale building by now, so there won't be any gross air
leakage, just what makes it through the plaster. I would treat the
earth bricks with silicate paint, which shouldn't hamper the
transpiring of moisture much.
I don't really want to do a typical brick veneer with an air space
between the bales and the bricks. Having done it before, I know that
it's nigh on impossible to maintain an even air space with a bale wall
unless you get into using wooden spacers or other material and time
intensive fixes. It seems to me that a patchwork of air gaps surrounded
by bales contacting the bricks would be worse than no air space at all.
So my option is use the bricks, or don't use any cladding and just make
the exterior plaster nice and square.
Let me know what you think...
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