The layer used to cover framed structures, including gypsum-based panels and plywood, is known as ...

• A. Insulation
• B. Drywall
• C. Sheathing
• D. Lath

Answer: (C)

The layer that covers the framed structure is sheathing. This material sits on the exterior side of the framing—over the studs in walls and over the roof or floor framing—and provides a solid base for the rest of the envelope. It ties the structural elements together and gives a surface for attaching the exterior finish, while helping to resist racking and support the weather barrier.

Gypsum-based panels and plywood are common choices for sheathing. Gypsum-based panels can offer fire resistance and a smooth substrate, while plywood provides stiffness and a strong nailing base for siding.

Insulation lives inside the wall cavities to reduce heat flow, not as the exterior covering. Drywall is the interior finishing layer installed on the inside of the framing, used for walls and ceilings. Lath is an older base for plaster in pre-drywall construction.