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RE: DQoD: "Lateral Torsional Support from Gypsum Board"

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We always assume that gyp board braces wall studs from buckling in the plane of the wall. I think then that it would work for lateral torsional restraint also. But what if your ceiling is dropped? I still think you wouldn’t need to design the roof rafters for lateral torsional buckling:

1)       the uplift stresses usually are very small

2)       I cannot picture a failure nor am I aware of any failure occurring where the roof structure failed because the joists buckled laterally during a wind storm

Maybe someone can correct me on that.


-----Original Message-----
From: Bill Polhemus [mailto:bill(--nospam--at)]
Tuesday, August 17, 2004 6:32 AM
To: seaint(--nospam--at)
Subject: DQoD: "Lateral Torsional Support from Gypsum Board"


Okay, so here’s the Dumb Question of the Day <tm>.


I’ve noticed that quite often design of roof rafters are governed by the wind uplift because they are supported laterally only at the supports, or perhaps with intermediate blocking.


Is it common to lend lateral torsional support via the use of gypsum board, such as ceiling drywall applied directly to the underside of the rafters? If so, what are the limitations (thickness, type, etc.)?