Why Doesn’t the Punched Casing Bead Work?
The punched casing bead has two 900 returns in the form
of the ground and the return flange. The shape alone forms
a dam the bottom of the wall that tends to trap water rather
than allowing it to exit the cementitious membrane, especially
if the paper is placed over the flange of the casing bead.
Secondly, the holes placed in the ground of the casing bead
fill with wet stucco when the section is stuccoed and this
nearly always results in plugged holes that will allow little
or no moisture to escape.
What is the Difference in the Foundation Weep Screed,
and Why Does it Work Better to Remove Moisture?
As discussed in the December 2003 issue of this newsletter
in detail, the foundation weep screed is described in ASTM
C1063 as an accessory used to terminate stucco at the bottom
of exterior walls. “This accessory shall have a sloped,
solid or perforated ground or screed flange to facilitate
the removal of moisture from the wall cavity and a vertical
attachment flange not less than 3 1/2 in. long”. Note
that the sloped surface can be punched or solid. This is
because the holes in the surface do not facilitate the removal
of moisture, but rather the entire surface of the angular
ground serves this purpose. The holes only serve as bonding
holes to aid in the bonding of the stucco to the foundation
weep screed. As the stucco cures and hydrates it shrinks
in volume slightly and results in a small crack or fissure
between the surface of the angular ground and the stucco.
Since the building paper is placed over the back nailing
flange during installation, any incidental moisture that
reaches the building paper can run down the wall to the
slope of this bead and exit the cementitious membrane.
Note that it is important if an acrylic or Elastomeric
finish is applied to the stucco surface that the installer
or painter is careful not to fill the crack at the junction
of the stucco and the foundation weep screed with finish
that might hinder the escape of moisture.
Below you will find a photo of a foundation weep screed
that has been installed on a framed wall. Also you will
see two drawings depicting the proper foundation weep screed
installation and the punched casing installation that is
not recommended by the author to be used as part of any
Foundation Weep Screed Located
at Bottom of a Framed Wall
Punched Casing Bead Incorrectly used as a
Foundation Weep Screed
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