Plywood shear wall nailing 1

[msquared48]

There used to be a clause in the UBC years ago prohibiting the use of dissimilar MATERIALS on opposite sides of a shear wall.

I do not remember if dissimilar nailing was mentioned for the same material on both sides of the wall though.

Does anyone know if the IBC has any restrictions on the dissimilar mailing (spacing) issue on opposite sides of a shear wall?

This scenario is applicable in remodels where there is an existing shear wall with known nailing, but the nailing cannot be increased for finish reasons, so another layer of plywood is added to the opposite side of the wall to add the shear needed.

First time I have had the question...



Mike McCann, PE, SE (WA)

 

[Celt83]

SDPWS Table 4.3A - Note 6:
Where panels are applied on both faces of a shear wall and nail spacing is less than 6" o.c. on either side, panel joints shall be offset to fall on different framing members. Alternatively, the width of the nailed face of framing members shall be 3" nominal or grater at adjoining panel edges and nails at all panel edges shall be staggered.

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[msquared48]

I see.

I missed the "on either side" part of the note.

Answers the question in a forest of trees, but answers.

Thanks.

Mike McCann, PE, SE (WA)

 

[dhengr]

Mike:
I don’t have the latest versions of those various codes/stds, or literature from the wood people, but have a couple thoughts for you. The dissimilar materials issue mainly applied to trying to make much use of (or sense of) sht. rock, ship lap and the like on one side with a good grade of sheet material on the other. The shear strength of the two sheathing systems were so radically different, in stiffness and nail shear strength, that they just didn’t work well together. And, it was judged to be a bad idea to try to combine the two system strengths for a total design strength. I believe I have seen some values for sht. rk., etc. on both sides however. And, we did know that the weaker sheathing systems did add something, and we could see it in studying wall/diaphragm failures, after EQ’s, etc. The plywd. took all/most of the load because the panels and their nailing were so superior, much stiffer. The weaker sheathing system just moved to much before (or as) it took any significant load. But, I suspect that as long as you are using comparable sheathing materials, even with slightly different nailing from side to side, you should have a fairly effective wall system. The increased stud width and other joint blocking should be fairly common out in your neck of the woods, with EQ’s, and all, and is always an issue with tight nail spacing at panel edges and the possibility of nail stager or even several lines of nails at an edge. The nails just start to turn 2x4’s into split mush when they are spaced to close, doubly so when applied from both sides. My understanding is that 3x4’s and 4x4’s are pretty common at panel edges out your way.

 

[msquared48]

They are, and that would be a problem in renovatons here.

Mike McCann, PE, SE (WA)