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RE: Glass Cracking

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How big are the window and are the headers supporting floor and roof load,
are there point loads over the windows? Any recent impact loads? You said no
signs of distress, maybe do a water level survey, check all doors windows
and cabinets for square/plumb. when was the house last painted has there
ever been any leaking i.e. shrink swell cycles? You may need to remove the
trim to see how it was installed. Check for equal diagonals of the window
opening for racking. I am sure you have thought of numerous possibilities:

header deflection
wood shrinkage
maybe they were installed too tight with no shim space for the rough
opening.
some windows have receiving channels for deflection space and racking

Jeff



> -----Original Message-----
> From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
> Sent: Thursday, August 22, 2002 1:52 PM
> To: SEAOC Listservice
> Subject: Glass Cracking
>
>
> Here's something that I hope one or more of you can give me an
> idea of what
> is happening.
>
> Two windows in a 2-story frame residence, one on the second
> floor, the other
> on the first floor.
>
> Window on the second floor is on the east side of the house.
>
> Window on the first floor is facing west, and under a porch overhang.
>
> Windows are double glazed, insulating glass.
>
> Interior pane on the window on the second floor has a parabolic
> crack similar
> to the shape of the SEA logo.  Crack started at the left jamb,
> proceeded up
> to the right, curved around and came back to the sill near the
> right jamb.
> Homeowner watched the crack develop and in 3-hours (8:00am to 11:00am) it
> progressed about 8-inches around the perigee.  (The homeowner marked the
> times on the glass.)  The exterior pane is undamaged.
>
> The owners report that the same type of parabolic crack occurred
> in the first
> floor window, with the interior pane cracking, not the exterior
> pane.  (The
> first floor window has been repaired.)
>
> The house is about 2-3 years old and there is no visible sign of
> distress in
> the house.
>
> Any thoughts, anyone???
>
> A. Roger Turk, P.E.(Structural)
> Tucson, Arizona
>
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