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RE: GSBN:Loadbearing sb with moisture damage



<x-charset windows-1250>I've just been reviewing some details from CASBA members--we're putting
together a CD of details that will be available, perhaps in six months.  In
a way, waterproofing is just the same as any good practice in conventional
construction, but...the big question is, if you have a pan under a window,
do you (or how do you) shunt any water collected there to OUTSIDE the
plaster wall.  Even here, there are conventional details from brick and even
stick construction.

John

John Swearingen
 SKILLFUL MEANS
design and construction
 www.skillful-means.com


-----Original Message-----
From: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of Chug.
Sent: Wednesday, March 08, 2006 8:45 AM
To: GSBN
Subject: Re: GSBN:Loadbearing sb with moisture damage


Hi David

Thanks for this, I was just going to ask what are peoples latest 'best
practice' methods for the waterproofing detail of SB window and door
openings, as this is one area where I feel there is not much info out there
and even less in pictures, anyone else got anything on the subject?

bale on
Chug
chug@...<a  target="_blank" href="http://www.strawbale-building.co.uk/";>http://www.strawbale-building.co.uk/</a>
.
----- Original Message -----
From: strawnet@...
To: GSBN@...
Sent: Wednesday, March 08, 2006 3:52 PM
Subject: Re: GSBN:Loadbearing sb with moisture damage


Laura, Chris and all,

The issue of good moisture detailing for windows is, in my view, one of the
most important and most often neglected aspects of sb design and
construction. When you talk with the people who look at moisture failures in
buildings for a living, this is often cited as the most common or one of the
most common areas of moisture damage and failure.

  It is a more important issue to get right in bale walls because they are
susceptible to moisture damage. That it is so often a problem in
conventional construction should not make us less vigilant or diligent. And
this is important - good design and detailing should never rely on caulking
as the only method of preventing moisture from getting into the walls around
windows.

Here is my ideal scenario - what I would like people thinking about as they
design their detailing for openings in bale structures. There should be
flashing all around the opening that is, in essence "shingled" - overlapped
starting from the bottom, so that any leaks are directed onto (not behind)
the next piece of flashing, and eventually, out of the wall. There are a
number of products available with which to do this and this is one place
where I think the judicious use of synthetic materials makes a great deal of
sense. This flashing should not just be applied over the surface of the
plaster, but should start, ideally, behind it so that the plaster is
actually part of the shingling system.

I'm a big proponent of having a sill pan (which can be made of hard or soft
waterproof material - could be the same material as the rest of the
flashing), which extends underneath the window and a bit beyond each side of
it, is turned up at the back and sides (so that water can't run off the back
or ends into the wall), preferably slopes to the outside, extends beyond the
exterior finish surface, and has a drip edge.

The less weather exposed the window, the less critical this detailing is.
But if the wall above the window is going to see rain, ideally we would have
a piece of flashing that extends above the top of the buck and up behind the
plaster. I know this is a challenge, especially if you are cutting an
opening into the wall after plastering. But if the top of the buck had even
a small strip of wood nailed to the top and set back so that it was behind
the inside surface of the exterior plaster, the flashing could be attached
to the top of this strip and extend out and down the face of the top of the
buck. It should be long enough to be able to  overlap over the top of the
window as well as the top of the side flashing. Then, moisture that got to
the inside face of the stucco above the window, and moisture that leaked
behind the trim at the top of the window would not be able to end up inside
the wall or sitting on top of the window buck or the top of the window.

It is important to note that caulking, even the best caulking, is only going
to reliably last a few years. If it is all that you are depending on to keep
moisture out, and it is hidden by trim or in places you rarely or ever
inspect and maintain, you have designed in a problem rather than designing
it out. It's much easier to think these things through before you build and
if it's too hard to visualize this, build a mock-up, a model, of what you're
thinking about building and work out the details at full scale where you can
try different things and even test them...

When I was building, I used to try to think like water - how could I get in
and how could I get out. Use great care in your efforts to keep water out,
and, knowing that you will not be able to achieve this completely, take as
great an amount of care making sure that the water that does get in can get
out. Of course I also used to think that you "only had to be smarter than
water" to do this and it turns out that like many others, I had woefully
underestimated the IQ of water...and similarly overestimated my own...

What  I love about this forum is that we are, as a group, so interested in
learning from our own and others mistakes and discoveries and sharing that
learning openly.

David Eisenberg

 -----Original Message-----
 From: Laura Bartels laura@...
 To: GSBN GSBN@...
 Sent: Tue, 07 Mar 2006 20:50:30 -0700
 Subject: Re: GSBN:Loadbearing sb with moisture damage

  Regarding cutting out windows after basecoat (or all coats) of plaster,
  I have always scratched my head over doing good moisture detailing after
the window does go in. Any comments?  Laura

 Chris Magwood wrote:

 > From our point of view, it took about the same amount of time to  > frame
everything up first and then stack and plaster compared to  > stacking and
plastering and cutting out later. The reason we didn't  > keep doing it this
way? Well, what do you do with a bunch of 3x5  > foot, 21-inch thick hunks
of bale wall that weigh hundreds of pounds  > each?  >  > Chris  >  >  >
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For instructions on joining, leaving, or otherwise using the GSBN list, send
email to GSBN@...HELP in the SUBJECT line.
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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.  
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