Which materials are typically used for exterior wall sheathing?

• A. OSB or Plywood panels
• B. Fiberglass insulation
• C. Vinyl siding
• D. Stucco

Answer: (A)

Exterior wall sheathing provides the structural surface that stabilizes the wall and gives a solid base to attach siding. OSB and plywood panels are used for this role because they deliver the needed strength and stiffness to resist wind loads and provide a flat, continuous surface for fasteners and weather barriers. Fiberglass insulation belongs in the wall cavity to reduce heat transfer and does not provide the structural nailing surface you need for sheathing. Vinyl siding is a finish you apply over the sheathing, not the sheathing itself. Stucco is another type of exterior finish that is applied over a substrate (often over sheathing with a lath), not the sheath­ing material. So the typical exterior wall sheathing materials are OSB or plywood panels.