OSB shear walls stiffer than ply - is OSB or ply the industry norm?

[AaronMcD]

Hey, while trying to get enough stiffness out of wood shear walls, I've run across the HDU holdowns and OSB as the stiffest options. But try as I might, I can't find anything online talking about plywood vs. OSB for shear walls. Is there a disadvantage for OSB? Why doesn't everyone use OSB since it has something like double the stiffness? Would it be wrong of me to start using OSB as my shear wall default?

 

[jayrod12]

Around here OSB is the norm, only because it's cheaper by a mile. The biggest drawback to OSB is the durability when exposed to moisture. Plywood has some resilience, OSB turns to dust.

 

[Mjkkb2]

I have been using the OSB or Plywood interchangeably for shear walls. WE always specify either or as acceptable so long as the grade is what we have specified (usually Structural 1). I frankly was not aware the stiffness is different between the two. How do you figure that?

 

[AaronMcD]

NDS provides different stiffness values in their shear wall tables.

 

[CANPRO]

I'm sure I'm not the only one here who has pulled handfuls of OSB out of a wall that had a leak. But in my area, if you specified plywood on a shear wall its very likely you would either get a phone call asking to substitute for OSB or you'd go on site and see OSB on the wall.

 

[NorthCivil]

The Canadian wood design manual lists OSB and plywood as equivalent for shearwall strength. I imagine there must be a fair amount of research to back it up.

Coming from the wet coast, i think building envelope issues have been more or less sorted in the past 10 years where it is reasonable to assume that your wall will stay mostly dry - at least not saturated for a long time, where rot would start to be an issue. And buildings that begin to rot are usually addressed within a few years.

One thing that still bothers me about OSB shearwalls though, is I am unsure how nth cycles of wetting and drying would affect the integrity of the panels, even if the OSB doesnt stay wet long enough to rot. Also there is the issue of the OSB getting wet during the construction - OSB swells and the nail head will partially puncture the panel.

 

[Mjkkb2]

Shear capacities are the same in the US also but the stiffness values are not. I guess the OP was referencing the NDS SDPWS table C4.2.2A, AaronMcD - is that what you mean also? I have to say I never realized this so thank you for education.