Comments bellowed:<br><br><br><div class="gmail_quote">On Tue, Feb 10, 2009 at 11:45 AM, RT <span dir="ltr"><<a href="mailto:ArchiLogic@yahoo.ca">ArchiLogic@yahoo.ca</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Date: Mon, 9 Feb 2009, John Swearingen <<a href="mailto:jswearingen@skillful-means.com" target="_blank">jswearingen@skillful-means.com</a>><br>
wrote:<br>
Re: Lime plaster and expansion joints<br>
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<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
We know that the steel reinforcing in reinforced concrete works because the coefficients of thermal expansion are similar for the two materials so I<br>
don't think that the cracking that Jeff is talking about is due entirely to juxtapostion of the two different materials, plaster and steel.<br>
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<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Well.....I dunno about coefficients, but I have seen cracks along steel<br>
members. I think what happens is that the steel superheats while the skin doesn't.<br>
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That's more about temperature differentials rather than different coefficients<br>
isn't it ?</blockquote><div><br>Yes, I guess that's more the point. <br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>
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<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
In an infill bale wall, this might mean pre-stressing the mesh by pulling down to the foundation and/or sill plate only and providing a connection at the top of the panel that only restricts lateral movement of the panel.<br>
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<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
Now who's gonna do that?<br>
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I do it with any construction (ie whether it be something small like a
piece of furniture or large, as in a building ( ie With a sliding dovetail stiffenning rib to restrain a table top you would fix only one end of the rail. With wide plank flooring you fix only the tongue edge. With a large pane of glass you allow clearance on three edges ) where there are going to be different rates of movement between different components whether the<br>
movement be due to humidity, temperature or structural loading so I don't see why one wouldn't do it with a plastered wall panel.</blockquote><div><br>It's just that here in earthquack country, we are required to make our mesh very, very tight so that slippage does NOT occur when the ground moves the building.<br>
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<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
I would venture that a panel size should probably<br>
not exceed 144 sq ft., with control joint spacing in any direction not<br>
exceeding 12 ft whereas with Portland cement mixes, [snip]<br>
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<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
All very well, but what about the fact that you're making a crack in a wall that doesn't have a paper backing to deal with the water than comes rushing in?<br>
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Which begs the question: Why would you *not* install proper flashing
at a control joint knowing full well that there will be a crack at
that location ?<br>
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True, that flashing would not be a strip of paper simply because it
wouldn't do much good against a bale substrate but the presence of a flashing
(or perhaps more appropriately named a "drainage plane") at that location is still essential.</blockquote><div><br>Right. You would have to install flashing paper over all or most of the bale wall in order to keep water out of the crack made by an expansion joint. Where would it all end, I ask you? We want the plaster to bond with the bales for a variety of reasons, among which I would include laziness on our part, and bale/plaster adhesion that is important structurally.<br>
<br>With care we can limit cracking and/or seal/patch cracks that occur and so limit any leakage and subsequent damage to an acceptable level. There is a pitfall here, though, because the owner and future owners have to assume a degree of vigilance and responsibility to survey the building for new cracks.<br>
<br>John<br></div><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br><font color="#888888">
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-- <br>
=== * ===<br>
Rob Tom<br>
Kanata, Ontario, Canada<br>
< A r c h i L o g i c at ChaffY a h o o dot C a ><br>
(manually winnow the chaff from my edress in your reply)<br></font><div class="WgoR0d">
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</div></blockquote></div><br><br clear="all"><br>-- <br>John Swearingen<br><br>Skillful Means<br><a href="http://www.skillful-means.com">www.skillful-means.com</a><br>