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RE: Out of Plumb Trusses

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My experience (guess) tells me that these trusses were warped during
shipping or were stored incorrectly at the jobsite.  Whenever encountering
such a situation in an existing building, I have required additional
continuous solid blocking be installed at the top and/or bottom chords as
required (or desired so you can sleep easy at night) to prevent the local
buckling failure of one truss.  The blocking helps keep all of the trusses
in their as-built position and reinforces the diaphragm bracing action of
the plywood roof sheathing.  

William J. Keil, P.E.

-----Original Message-----
From: Robert Fennema, P.E. [mailto:bobfennema(--nospam--at)]
Sent: Tuesday, August 31, 1999 9:22 AM
To: seaint(--nospam--at)
Subject: Out of Plumb Trusses

I have a client who is considering the purchase of a 60 odd unit
apartment complex. There are six buildings all two story.  They were
complete in 1984.  When inspecting the roof framing, I found several
dozen trusses that are out of plumb. I found panel points up to 5 inches
off center. There are also top chords that are misaligned between panel
points.  The truss span 48 feet and have an intermediate support point
at the mid span over the partition between the units.  The roof
sheathing is 1/2 plywood.  The lower chords are supported by gypsum
drywall on resilient channels.

I am convinced that the rooof framing has not moved as the these
conditions are random.  In some cases a truss will lean east while the
adjacent one leans west.  

According to the City records, the tusses were designed by Truswal but I
do not know the local supplier. 

How can I evaluate the significance of these conditions?  How can these
conditions be repaired since removing the roof sheating is not very