Effect of ridge vent (unnailed plywood edge) on structure 1

[smartbuilder]

I have been told by the inspectors that roof plywood needs to be nailed at the ridge and at the eave blocks to provide a proper "diaphragm". Yet To provide continous ventilation in the rafter bay between the eaves and the opening at the continous ridge vent I cannot install blocking or a ridge board for nailing without restricting the air flow between the eaves (exterior wall) and the ridge vent. Assuming installed insulation that provides an inch of space at the top of the rafter bay for the ventilation.

This is specifically in regards to a standard framed residential roof with rafters set on top of a ridge beam that spans 18' and 14' for a total length of 32'. I have sometimes seen simpson straps installed over the ridge from rafter to rafter....does this tie the diaphragms together? Any suggestions or explantion of this would be great.

 

[COEngineeer]

smartbuilder they usually use strap only when you use ridge beam with I-joists rafter. Usually people tend to use flush ridge instead and use lssu hanger. If you drop the ridge then you have to use blocking between I-joist and then strap the joists together. The reason you need to strap them together is because you cant really toe nail an I joist onto the ridge board. I never specify dropped ridge beams w/ I-joists for that reason.

As far as ventilation, I do not know. I always leave it to the architecht.

 

[wjsd]

I found a reference to this in the APA literature called "Introduction to Lateral Design" which states that "A continuous ridge vent can be used with an "Unblocked Diaphragm". An unblocked diaphragm has no requirement for blocking between unsupported edges of adjacent panels. It also states you could stagger the blocking in a "blocked diaphragm" allowing vents every other truss bay. You then provide double the nailing requirement at the blocked bays. So you have two choices: design the diaphragm as unblocked or stagger your vents. I don't know your ventilation requirement, so that could dictate which one you use.
APA produces tons of literature to guide you.

https://www.apawood.org/

Good luck...

 

[JD2]

I'VE USED DETAILS WHERE YOU DRILL HOLES IN THE BLOCKING TO ALLOW FOR AIR MOVEMENT. SIZE AND NUMBER OF THE HOLES DEPENDS ON THE DEPTH OF THE BLOCKING AND THE SHEAR FORCES YOU ARE TRYING TO TRANSFER. DON'T KNOW HOW THAT INTERFACES WITH YOUR INSULATION LAYOUT THOUGH.