Perimeter
caulk, also known as sealant, is used to transition windows to adjacent
claddings; we call this a perimeter isolation joint. The windows and claddings resist water and air
infiltration with the help of the weather resistive barrier (WRB) at the
cladding substrate. The area between the
cladding and WRB is known as the drainage plain. In a recent blog post, I
defined and quantified the volume of water that the drainage plain should be capable
of managing. Water at the drainage plain is
commonly referred to as incidental water.
The incidental water should be controlled and directed to the exterior. The interfacing of the weather resistive
barrier at openings in the wall is critical but, because the weather barrier
interfacing occurs behind the surface of the cladding and abutting components,
it is often undervalued.
In this video,
we are utilizing a putty technique to create a dam that isolates the corner of
a window. Water is then applied to the surface of the window within the
dam. This is a modified version of the
sill dam test outlined in AAMA 502-02 Voluntary Specification for Field Testing of Windows and Sliding Glass Doors and is similar to the Rilem
testing shown in our Rilem tube post.
As shown in
the video, water by-passes the window sill/jamb framing. The area where the water passes through the
frame is behind the manufacturer’s prescribed location for the window perimeter
isolation joint. The demonstration shows
the path that water can take to infiltrate behind the cladding. This window manufacturer has sealant and pan
flashing requirements that would protect against this source of “incidental
water”. The requirements were improperly
executed, leaving the building vulnerable to water infiltrating the cladding
and framing.
I doubt the
builders were aware that water would so easily pass to the area behind the
perimeter isolation joint on this window.
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