ca s e st u dy
02
04
While these filler pieces had been fitted and
sealed, incompatibility between the sealant
and the coated aluminium allowed water to
bypass the filler pieces and be deposited
on the top edge of the glass panel below.
This then allowed leakage to the interior, as
shown in diagram 03.
01 Water leakage visible at transom-to-mullion
joints.
02 Cross section of a transom-to-mullion joint.
03 Path of water through a mullion pocket.
Illustration by Danielle Hynard.
04 Airflow through a window system.
Illustration by Danielle Hynard.
Lesson: Bond test the sealant to be used
for fitting foam fillers in mullion pockets to
ensure compatibility with substrates and
foam.
OVERFLOWING SUBSILLS DURING
WATER LEAKAGE TESTING
The AWA’s publication, ‘Installation: An
Industry Guide to the Correct Installation
of Windows and Doors’, gives the following
guidance:
• Carry windows in the vertical position
with sashes locked.
• Do not rack frames out of square.
Rotating unbraced and glazed windows
places stresses on frame joints which would
otherwise never be encountered. This is
not accommodated by frame joint design,
leading to failure of small sealed joints and
consequent water leakage.
Lesson: If the rotation of window units after
manufacture cannot be avoided, the units
must be braced to prevent racking.
WATER LEAKAGE FROM TRANSOMS
AT THE TOPS OF GLASS PANELS
Pressure-equalised windows are designed as
discrete systems. When testing the installed
units to Australian Standard AS 4420.5,
constant air pressure at the subsill drainage
slots prevented drainage and the water
within the subsill was blown over the end
dams. This was because the façade, as a
whole, was not pressure-equalised: the
cavities on the masonry façade were not
closed at the window openings allowing air
within the window system to pass into the
building’s façade cavity, as shown in diagram
04.
Redesign of the window jamb details was
needed to close the cavities and to enable
the windows to perform as designed.
Lesson: The published performance of
windows relates to discrete tests: Be mindful
of the effect of installation methods.
Foam filler pieces fitted into mullion pockets
at transoms are intended to capture and
divert water from the mullion pocket into the
transom for drainage, as shown in image 02.
Windows Magazine Summer 2016
11