We are building a shear wall by adding structural-1 plywood or OSB to the existing framing and nailing according to a nailing schedule. The wall is 13'x8'.
What is the best way to orient the plywood for the best shear strength and nail retention?
the wall is 13x8 and the boards are 4x8, the simplest way is to put the 8 dimesnion of the boards on the 8 dimension of the wall.
As the boards need to be nailed all round the perimeter, if you lay the boards horizontally you'll need to add blocking to catch the edges of the boards.
If you stand them vertically you'll need a stud where the edges of the boards meet. It looks like you have 16" spacing for your studs, so you'll only need to cut the end boards (and a hole for the electrical panel id that needs to be accessible from the side you are boarding)
When properly nailed both orientations are equal in strenngth
Are you trying to solve a specific problem with the structure? If so, you might indeed want to engage an engineer.
If you are simply trying to add a little rigidity to your building, plywood is a good choice. It will work in either orientation, but horizontal brick pattern is most typical. Consider tying the ends (and sides) together with sheathing brackets, like this:
They will add a great deal of shear resistance at a minimal cost.
Fixing boards to a wall or ceiling can in fact make the structure less safe because it changes how earthquake forces act on other parts of the structure. Eg having one wall made stronger may transfer force in an unexpected way to a weaker member that fails that would not otherwise fail. The diversion of these forces might mean that you need to strengthen something somewhere else in the structure.
It is better to have an engineer who understands the structural design process to make sure a shear wall is in fact a good idea.
