Which sequence correctly lists the components of a wood frame exterior wall build-up from inside to outside?

• A. Interior wall finish, Polyethylene vapor barrier, Insulation, Wood frame, Plywood sheathing, Building paper, Exterior siding.
• B. Interior wall finish, Insulation, Polyethylene vapor barrier, Wood frame, Plywood sheathing, Building paper, Exterior siding.
• C. Insulation, Wood frame, Plywood sheathing, Building paper, Exterior siding, Interior wall finish, Polyethylene vapor barrier.
• D. Interior wall finish, Polyethylene vapor barrier, Wood frame, Insulation, Plywood sheathing, Building paper, Exterior siding.

Answer: (A)

Moisture control and proper structural layering guide the order of a wood-frame exterior wall. From inside to outside, you begin with the interior wall finish, then place the polyethylene vapor barrier on the warm side of the wall to stop moist indoor air from diffusing into the cavity. Next comes insulation in the stud cavity to reduce heat loss. The wood frame (studs) provides the structural backbone and sits outside the insulation. Outside the studs, attach exterior plywood or OSB sheathing for rigidity, then add building paper or house wrap as a weather barrier, and finally the exterior siding. This sequence matches interior finish, vapor barrier, insulation, wood frame, plywood sheathing, building paper, and exterior siding.