[GSBN] Flashing behind control joints + detailing for earthquacks

[RT]

On Tue, 10 Feb 2009 John Swearingen <jswearingen at skillful-means.com> wrote:

Re: Control joints (was Re: Lime plaster and expansion joints)
>> 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.

> 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.


First, I disagree that in order to properly flash a control joint, that  
one would have to apply paper (presumably asphalt impregnated felt (AIF)or  
such-like ?) over all or most of the wall.

Any water that gets through the control joint (which in some cases is also  
a flashing ie the plast-echhh! stuff) or any joint in the plaster can be  
retained in the area immediately behind
the joint simply by using a flashing that has edge dams along the  
longitudinal edges to limit lateral movement of the water before it has  
the opportunity to run down the flashing and be shed out of the wall.

That drainage plane flashing likely wouldn't be AIF although I suppose one  
could try and
figure out how to make AIF work (probably in conjunction with a second  
material as a base.

It would more likely be brake-formed sheet metal or rubber.

The EPDM  rubber glazing bed gasket that is used for sloped glazing comes  
to mind but it may be a bit narrow (~2.5 inches) for some people's liking.

Also, the EPDM rubber gaskets that are used under wall panels, sills  
plates etc would do the trick I think and they are available in stock  
widths up to 6 inches (nominal). (see BG65 at the link below)
    http://www.conservationtechnology.com/building_gaskets.html

A person could make up something similar using strips cut from EPDM sheet  
stock (ie roofing or pond liner) + screen spline + contact or rubber  
cement if the store-bought stuff is unavailable or deemed unsuitable.

But that being said, if a bale wall is going to be exposed to driving  
rains, plaster adhered to bales probably isn't the best choice as the  
weather-exposed cladding. A ventilated/drained rainscreen cladding would  
be a better choice. The rainscreen cladding could still be plaster of  
course but it would be most easily configured as a pre-cast tilt-up panel.

                 			*

the Skillful Meany also wrote:

> 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.

So is that the latest name for Californians ?  " Earthquacks" ?  I like it.

I don't see why it wouldn't be possible to have "very, very tight mesh"  
without
attaching it to both the foundation and a steel spandrel beam at the top
of a steel-framed wall.

The mesh would be tensioned by precompressing the bale wall panel and then  
fastening the mesh at the bottom ends (ie inside and outside) only, to  
wood nailers anchored to whatever the bales are sitting on before  
releasing the precompression device, in a manner similar to how a SB  
garden wall would be stabilised by precompression using the mesh as the  
tensile element.

At the top end, the mesh would either be looped over the top of the  
pressure plate (ie a box beam)
or fastened to the chords of the box beam pressure plate.

The top of the precompressed panel would just have to be restrained from  
lateral movement (after precompression is completed) , by clips at the top  
of the wall panel to the spandrel beam and at a few points along the  
height of the column, all allowing vertical movement of the panel.

No ?

-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  ChaffY a h o o  dot  C a >
(manually winnow the chaff from my edress in your reply)
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