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GSBN: Digest for 10/25/04

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-> Re: GSBN:Re: Moisture in SBW
     by John Swearingen johns@...


Date: 25 Oct 2004 17:47:02 -0600
From: John Swearingen johns@...
Subject: Re: GSBN:Re: Moisture in SBW


>Hello Danny, et al...
>I just wanted to throw in a few cents worth of comments on this subject
>as I have been involved in a few houses with minor to major moisture
>problems. Generally they have been as the Master of Moisture, John
>Straube, described - related to poor design decisions and/or poor
>detailing around windows, etc.
>My basic design philosophy in general -
>First principle - Design problems out of, not into buildings. In other
>words think about what you're doing and what is going to happen over time
>and how you can mitigate the bad things by design rather than through the
>application of technology, high-tech materials, etc.
>Second principle - Simplicity is its own reward. This makes carrying out
>the first principle much easier...
>Third principle - The roof should cover the tops of the walls...and then
>some. This should be an absolute no-brainer for straw bale. Many of you
>know my long-standing dislike of Santa Fe style architecture, but this
>goes double for straw bale - parapet roofs, vigas sticking out of the
>wall, roof drains penetrating the walls - all totally violate the first
>two principles.
>Some of you may have heard me say this before, but for those who haven't
>- a few years ago a woman asked during a presentation I was giving if it
>wasn't true that straw bale buildings should only be built in dry places.
>I said, after pausing to think about it, "Yes, that is true. But, you can
>design and build dry places just about anywhere. Which is how I would
>like you to think about what you're doing when you're designing a straw
>bale building."
>So, Fourth principle - design dry places for your bales...
>Okay, enough pontification...
>The last thing I'll share is about windows and window sills. John aptly
>pointed out that they leak - they always leak (unless you've been smart
>enough to design them into really dry places). So protecting the bales
>beneath the windows requires that you catch the water under the window
>and make sure it gets all the way out of the wall. In other words,
>ideally you would have a pan of sorts under the window, sloped slightly
>to the outside, extending a bit beyond each side and with a lip at the
>back and on each end (so water can't just run off the ends), and
>extending out beyond the exterior wall surface, with a drip edge - so
>that any water that leaks through or runs down the sides of the window
>ends up in this pan and is shown the exit. You can make these pans out of
>metal, plastic, ice and water shield, cast this shape into a concrete
>sill, anything that will keep the water from leaking through it, but the
>principle thing here is to make sure that the water can't get into the
>wall below the window. You can put your window sill material, whatever it
>is, on top of this pan flashing being careful not to punch unsealed holes
>in it when you install the sill. It can take a little thought and
>ingenuity to do this, but it assures you that when the windows leak the
>water leaves the building.
>That old practice of just putting roofing paper or plastic over the top
>of the bales and setting your windows on it and then plastering over it
>just leads the water down inside the plaster to the bales wherever the
>water protection ends unless it runs continuously down the wall under the
>window to below the bales (and we don't recommend doing that). It just
>temporarily moved the problem down, didn't solve it.
>That's all for now. Glad to see this discussion here.
>David Eisenberg, Director
>Development Center for Appropriate Technology
>P.O. Box 27513, Tucson, AZ  85726-7513
>(520) 624-6628 voice / (520) 798-3701 fax
><a  target="_blank" href="http://www.dcat.net";>http://www.dcat.net</a>
>The Development Center for Appropriate Technology is a 501(c)(3)
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I was going to comment on this issue, but David has said everything
there is to say, clearly and (imagine this!) succiently.

John Swearingen


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