Staggered seams on roof sheathing.

[Daddy-0-]

Is there a requirement to stagger panel breaks on roof sheathing or is it just good practice? We don't do a sheathing inspection but the other day I saw the framers sheathing a roof with the plywood edges not staggered. I looked it up and the code section tells you to stagger or not stagger according to the nailing schedule chart which tells you nothing. They also reference an APA standard which I am going to look up on Monday. Thoughts.

 

[fatboy]

I'd have to research, but I suspect it is a practice, rather than a rule. Not in the code anyway. Being a carpenter by trade, I can tell you that staggering keeps everything nice and even..........but other than that? Other opinions?

 

[brudgers]

The staggering of joints in the roof diaphragm affects loading and blocking requirements.

See the diagram at the end of [iBC] Table 2306.3.1

[edit: don't know if there is an equivalent in IRC]

 

[fatboy]

Good point, makes sense. Will have to wait till Monday to research IRC.

 

[Daddy-0-]

We always staggered each row of sheathing by two joist bays because it makes the roof stronger. I know it's good practice and I thought it was required to stagger at least one rafter bay but I think I may have been wrong.

 

[brudgers]

We always staggered each row of sheathing by two joist bays because it makes the roof stronger. I know it's good practice and I thought it was required to stagger at least one rafter bay but I think I may have been wrong.

The determining factor in IBC is either all the edges are blocked and the joints are staggered and the panels have their long edge across the rafters/trusses - in which case you get a higher allowable shear - or they ain't and staggering the joint doesn't matter.

 

[DRP]

APA's "Diaphragms and Shearwalls" L350A has a good set of tables showing the strength of various blocked and unblocked sheathing methods. If this were framed the way I would typically do it the unblocked but staggered roof diaphragm would have 240#/' allowable shear where with their method it would be 180#/'. If it's not a code issue it might just be a word to the wise, it wouldn't cost a thing to make the roof a good bit stronger.

 

[steveray]

Another thing often missed in the IRC is the span tables for sheathing are based on a min 24" or wider panels...footnote c I believe....sheathing table...been trying to nudge the guys into that one for a while now...or provide paperwork from the sheathing manufacturer...I just don't have time to research that one...