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Re: GSBN:Exterior cladding question



Tim,

Good point about including some lime. Wouldn't have done that, but it
seems wise.

This building is intended to act as a bit of test bed, so perhaps I'll
be able to remove a brick or two and see what's going on back there
after some time.

Chris

On 8-Feb-05, at 5:57 PM, Tim Owen-Kennedy wrote:

Hi Chris,

We have had to restack some bales against masonry surfaces, lime and
earth,
and our solution was to blow plaster against the wall and then smooosh
the
bales into it as we stacked them. This came from our concern about the
air
gaps and condensation and we figure the more or less contiguous
material
negates that sufficiently. Another aspect that has come up more in
walls
that have a wood wall in front of them, is that there is no good means
to
see if things are deteriorating behind the frame wall. So, we always
plaster
bales that are visually buried and we do that with lime or a lime
earth mix
to mitigate mold issues that would not be visible if they got started.
So I
would recommend that if you use a thick slip, plaster, or straw clay
between
the straw and the blocks that you consider some type of "fungal block"
in
the mix. In my opinion it's cheap insurance for an area you can't
easily
inspect over time.

Best of luck,

Tim


Tim Owen-Kennedy
Vital Systems, Natural Building & Design, Inc.
888.859.6336 PO Box 751 , Ukiah, CA 95482
www.vitalsystem.net

-----Original Message-----
From: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of Chris
Magwood
Sent: Sunday, February 06, 2005 7:38 PM
To: GSBN
Subject: GSBN:Exterior cladding question

Hello all,

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
floor.

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...

Chris

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----
GSBN is an invitation-only forum of key individuals and
representatives of regional straw construction organizations. The
costs of operating this list are underwritten by The Last Straw
Journal in exchange for use of the GSBN as an advisory board and
technical editing arm.

For instructions on joining, leaving, or otherwise using the GSBN
list, send email to GSBN@...HELP in the
SUBJECT line.
----