[GSBN] Drainage within a plaster system

[John Straube]

I is an engineer, but I would not trust engineers much without lots of input from the reality of the building site.
The inner stucco is likely the best shear resisting layer and I would rely on this.  Also a good fire barrier and wind barrier.
The exterior stucco needs to be attached well enough to not fall off in an earthquake or windstorm.  14 ga wires will do it if they are often enough.  In other uses, I have seen screws through metal lath used to support exterior stucco, but this requires about one screw per 1-2 square feet.

On 2013-07-08, at 9:09 PM, Frank Tettemer <frank at livingsol.com>
 wrote:

> I really like what you're doing with this, John!
> 
> The stitching of 14g wires answers all my concerns of the outer layer of render flaking off, or pulling away from the structure.
> And I imagine that this stitching would also reinforce the lateral resistance of the plaster, when it's ask to act as a wind bracing,
> and when it's contributing to seismic resilience.
> 
> Would any Engineers on the list want to confirm this? John and I are just builders, after all, and speaking for myself, I'm only qualified for driving nails, not engineering.
> (other than "intuitive engineering".
> I _may_ be qualified for that.).
> 
> Frank
> ........................................................................................................................
> John Rain Skeemer Swearington wrote:
> 
> We/ve used a similar product, with good success, by Benjamin Opdyke: http://www.benjaminobdyke.com/visitor/subcategory/subc/rainscreenProducts.
> 
> We applied it more or less as Frank says:  we used a thick scratch (base) coat of plaster over the bales, and then tied the rainscreen (Homeslicker plus Typar) and light stucco lath onto the building with 14g wires through the bales. The Typar stops the next plaster coat from filling the gap.  This sounds more laborious than it was; it went pretty quickly. Then we applied  a regular three-coat plaster, though a thick two-coat would also work.  We used a custom flashing at the bottom of the bottom of the wall to carry away the water.I see
> 
> This was in a highly exposed round tower sticking up through a tile roof, a fairly challenging location that receives high winds and driving rain.  We've gone through the first winter, including some hurricane force winds, with no sign of leakage :)
> 
> John "Rain Skeemer" Swearingen
> 
> 
> On Mon, Jul 8, 2013 at 2:04 PM, Frank Tettemer <frank at livingsol.com <mailto:frank at livingsol.com>> wrote:
> Hi Sven,
> 
> While this flexible drainage plain may well provide the needed path for intrusive water, and allow drainage from within the wall plaster,
> would it not also prevent bonding of the render to the straw bales in the wall assembly?
> 
> I'm imagining a 'brown' coat of plaster, worked into the exterior of the bales, and the application of the Duraflow material to this first plaster coat, while it is still wet and workable. Then the second coat of plaster covers the Duraflow material, yes?
> 
> Would this compromise the structural needs of the outer skin, in it's function for structural engineering and seismic resiliency?
> 
> Or, to say it all a different way:
> Wouldn't the use of the Duraflow weaken the strength of the wall assembly?
> 
> -- 
> Frank Tettemer
> Living Sol ~ Building and Design
> www.livingsol.com
> 613 756 3884
> 
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John F Straube
jfstraube at uwaterloo.ca
www.JohnStraube.com