Which option is not a typical exterior sheathing material?

• A. OSB
• B. Plywood
• C. 1x6 Straight or Diagonal
• D. 4x8 Wood Sheets - OSB or Plywood

Answer: (C)

Exterior sheathing is meant to be a stiff, continuous surface that ties the wall together and provides a solid nailing base for the siding. In modern construction, that role is filled by panels like plywood or OSB, usually in 4x8 sheets, which give uniform thickness, good shear strength, and a flat surface for the siding to grip.

A 1x6 Straight or Diagonal board is dimensional lumber, not a panel. It’s thin and narrow, would have seams and gaps, can warp or shrink, and doesn’t provide the continuous, rigid sheathing surface needed to resist wind loads and transfer lateral forces. It’s typically used for trim, furring, or interior framing rather than as exterior sheathing.

So the option that isn’t a typical exterior sheathing material is the 1x6 Straight or Diagonal board. The other choices—OSB, plywood, or 4x8 OSB/plywood sheets—are standard exterior sheathing materials.