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Re: Roof Sheathing at Ridges

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Disregarding the diaphragm action, wouldn't there be reasonably significant uplift along the free edge?  Yes, the rest of the sheathing edges are not blocked, but they are not in a transition zone and they have plywood clips (for what they are worth). 
 
I readily admit I don't know much about wood construction or residential, but it seems to me that it creates an "weak link" in the roof.
 
M. David Finley, P.E.
3810 South First Street - Suite 7
Lake City, FL  32025
386-752-6400
----- Original Message -----
Sent: Tuesday, August 06, 2002 12:24 PM
Subject: RE: Roof Sheathing at Ridges

Like I have said privately how does diaphragm shear Case 3 work for 2" opening that occurs at the ridge over a metal plated truss connection? Bending through the truss panel point? I think tests for unblocked diaphragms used continuous solid lumber.  There is normally not much shear at the center of a diaphragm but ridge vents are normally something people just ignore.
-----Original Message-----
From: Paul Feather [mailto:pfeather(--nospam--at)SE-Solutions.net]
Sent: Tuesday, August 06, 2002 8:14 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Roof Sheathing at Ridges

Depends.
 
Look at the basic diaphragms for wood construction.  We have values for blocked and unblocked diaphragms depending on framing / plywood orientation and direction of load.  The ridge condition really isn't any different from any other unblocked plywood edge.  Ridge vents are a little trickier because of the offset distance, but the basic mechanism is the same ( I do not know the specifics in your case, so I am generalizing).  The diaphragm shear transfer is in the joist across the grain.  The same continuous joint exists every four feet up the roof slope.
 
Particularly in small structure construction, the diaphragm spans are small, and the required load capacity is small.
 
 
----- Original Message -----
Sent: Tuesday, August 06, 2002 8:37 AM
Subject: Roof Sheathing at Ridges

I walked down the street yesterday evening to look at a house that is under construction.  The house is a 1-story with wood trusses.  It appears that a ridge vent will be used at the ridge line and I saw no indication of blocking near the ridge - in other words, the roof sheathing on each side of the ridge has a free edge (albiet only 2' long) between the trusses along the ridge line.  Is that typical?  I'm not a timber or house guy, but it seems to me that something more would be required there, especially in a high wind area.
 
M. David Finley, P.E.
3810 South First Street - Suite 7
Lake City, FL  32025
386-752-6400