Interior Shearwall Detail

[bdlc2k]

Hello, all
Please refer to the attached plan and section. My question is:1- When using a drag strut to transfer wind load to an interior shearwall, should the sheathing of the interior SW go up to the ceiling diaphragm (in red) or could it stay at ceiling elevation?
2-Also, should there be any sheathing above the drag strut? If I sheath up to the ceiling with blocking between rafters, do you even need a drag strut (Section 2)? Thanks for your input!

 

[msquared48]

The SW sheathing does not have to go up to the level of the diaphragm sheathing. The diaphragm nailing into the blocking/parallel joist and the subsequent attachment of the blocking to the SW double top plate is good enough. Just extend the sheathing to the top of the double top plate.

As for the second question, depends what is the drag strut. If the strut is compression blocking, then there will be sheathing over it. If it is a metal tension strap, then it can be placed over the blocking, or over the sheathing. Just depends on the situation. Whatever the drag strut is comprised of, it should be able to take both tension and compression.

Yes, I would use a drag strut, and emanating from both ends of the shearwall to the edge of the diaphragm, not just in one direction as you have shown.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[OldPaperMaker]

bdlc2k,
msquared48's answer is correct if the framing above the ceiling level is a truss. In that case the shear in the wall line is collected (dragged) from the diaphragm to the truss and into the shearwall below.

But, if the roof system consists of a ridge beam, rafters and ceiling joists and the diaphragm is the plywood on top of the rafter (not on the ceiling level) then the shearwall needs to go up to the inclined roof level. The collector (drag strut) still needs to extend in both directions to the edge of the diaphragms.

I believe that this applies to both SW1 & SW2 in your sketch.

 

[RFreund]

I agree with both Mike and papermaker. If it is a truss you will need to denote that it is a drag strut, if stick-framed you will need to frame and sheath the wall (or a second wall on top of the shear wall) to the roof/bottom of rafters.

EIT