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Re: Wood truss deflection space

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Dear Jeff:

I am presently involved recommending repairs on a project where these
conditions were ignored.  The end result was several hundred thousand
dollars in claims against the developer.  Use the Simpson clips and use
"floating corners".  The use of interior crown moldings nailed only to the
trusses is even better.  From my experience one or two percent of truss
projects see some type of truss uplift resulting in objectionable cracking.

John Schenne, PE
-----Original Message-----
From: Jeff Smith <smthengr(--nospam--at)sirius.com>
To: seaint(--nospam--at)seaint.org <seaint(--nospam--at)seaint.org>
Date: Saturday, August 07, 1999 8:46 PM
Subject: Wood truss deflection space


>I am working on a (under)funded housing project with 32 foot wood trusses
>that have a midspan DL deflection of .11" and about .25" TL deflection. The
>lower chords have a segmented "camber" of 1/8" per 10 feet so that the
>trusses do not bear on interior walls. Simpson makes truss clips that allow
>for deflection and a connection of the truss over non-bearing walls as well
>as ceiling sheetrock clips. The sheetrock clips are intended to be
installed
>such that the ceiling sheetrock is not nailed to the bottom of the truss
>within 16" of the non-bearing wall, so the sheetrock actually bends
downward
>to the top of the wall plates. Needless to say the drywallers are not
>enamored with this detail. The drywallers want to install the sheetrock to
>the bottom of the truss at interior walls. My question concerns the
>deflection detail for the ceiling sheetrock. We are looking at maybe
>.14-.16" of LL midspan deflection for a 32 foot span. Are the any
reasonable
>alternatives to avoiding the ceiling sheetrock deflection detail. I know
>that this detail is many times ignored, yet others are steadfast in
>declaring its importance.
>
>Regards,
>
>Jeff Smith
>
>
>