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Re: Roof Sheathing at Ridges

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In testing pitched (sloped) roof diaphragms at APA, we found that the
ridge joint was critical since both sheathing and framing end joint
discontinuities occur at this location.  In tests of common (flat)
unblocked diaphragms, the framing is continuous at the sheathing side
joint.  Yes, the sheathing attachment can be standard, but remember that
at the ridge, the unblocked edge has fasteners spaced 16" or 24" oc,
typically.  The roof framing joint at the ridge is weak in resisting
shear forces perpendicular to the framing. Therefore, additional framing
and sheathing attachment may be required to resist these forces at the
ridge, and transfer them to the other side of the diaphragm.

I recall talking to an engineer in the SF Bay region about "creaking
sounds" heard near the ends of a commercial building with a pitched roof
diaphragm, on windy days.  We agreed that it was likely that the sounds
were from the roof framing connection at the ridge, and sheathing
fasteners working to resist high shear  forces at this location.
Structural upgrading was suggested to reinforce the ridge connection to
resist shear forces at the ends of the diaphragm.
John Rose
APA (retired)
Tacoma, WA


Jim Kestner wrote:

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