The best type of nail for attaching plywood sheathing is:

The ideal choice for attaching plywood sheathing is #8D nails. These nails are approximately 2.5 inches long, which provides sufficient penetration into the underlying structure—typically framing members like studs or beams—to ensure a secure hold.

When fastening plywood sheathing, it is important to use a nail that is long enough to penetrate deeply into the framing while also being appropriately sized for the thickness of the plywood being used. #8D nails strike a good balance between strength and ease of use, allowing for effective fastening without splitting the plywood or needing excessive force to drive them in.

Other sizes may not provide the same level of effectiveness. For example, #6D nails are shorter and may not penetrate deeply enough, leading to potential issues with the integrity of the sheathing. On the other hand, while #10D and #12D nails offer increased length and holding power, they may be overkill for typical plywood applications, making them more challenging to drive in without causing damage or misalignment issues. Furthermore, using larger nails when not necessary can increase labor time and costs without providing additional benefits for sheathing tasks.