Apr 09, 2004 · Typically if the wall exceeds 350# per foot load (lateral) or nail spacing is 3"oc or closer then this size of material is required. With a 2x sill plate and plywood shear on each face of the wall you can imagine what the sill will look like. If a 2x plate will work with the loads then a 3x plate does not afford you any better structure.