shear wall sheathing

huangyhg

shear wall sheathing
how high does the plywood sheathing need to extend for a shear wall on a wood framed wall?  to the bottom chord of the truss? to the top chord of the truss?  reasons?
to the roof diaphragm, whatever level that is at.
csd
it typically extends to the top of the shear wall, which is at truss bearing level.  this brings up the valid concern of "rolling" of the trusses, because the roof sheathing is several inches above this level.  some engineers add blocking between the trusses to prevent this rolling effect.  i typically don't worry about a gap between the roof sheathing and the top of the shear wall of less than a foot.
daveatkins
is the only need to bring the sheathing to the top of the truss to prevent rolling?  is there a need for shear force transfer at all?  i have a situation where i don't think it can reach all the way to the roof diaphragm.
you need a complete lateral load path.
are you talking about shear walls on the exterior of the building where the trusses bear?  or other shear wall?
i'm talking about an exterior shear wall on a non load bearing wall....parallel to the truss.
there should be some sort of "gable end truss" (or monoslope top chord end truss) on top of the end wall.  the sheathing should cover this end truss and extend up to the roof diaphragm.  there may be some 2 x 4 outriggers cantilevering over the end truss, preventing the sheathing from extending to the roof sheathing, but this is not a big deal.  if you have outriggers and are concerned, add blocking between the outriggers.
daveatkins
why does the sheathing have to cover the truss though?  isn't the truss designed to take the shear into the bottom chord, which in turn is connected to the top plate of the wall studs?
quote:
isn't the truss designed to take the shear into the bottom chord,
not usually unless the engineer of record requires it.  most trusses are designed solely as gravity components and any lateral load brought through the truss is not provided for in the "standard" truss designs unless the design plans require it....even then i'd wonder if they would do it as i don't think the typical truss software that is used provides for that sort of loading.
so usually you use sheathing or other means to provide the complete load path required.
i have specified metal stud endwall trusses to be used as shear trusses and calculations were submitted by the manufacturer supporting this. i dealt with nutruss and i re  
the shearwall sheathing should extend to the top of the shearwall double top plate on which the trusses bear.  the blocking between the trusses prevents rollover of the trusses.  the edge nailing of the roof sheathing is connected to the blocking and other mecnanical connectors connect the blocking to the wall double top plate.  hence, the full vertical load path.
mike mccann
mccann engineering