Framing & StructuralQuestion 350 of 700
Behind exterior cement plaster (stucco) applied over wood-based sheathing, how many layers of water-resistive barrier does the code generally require?
a.One layer
b.Two layers of a water-resistive barrier (for example, two layers of Grade D paper)
c.No barrier if the stucco is thick enough
d.Only a vapor barrier on the inside
Explanation
Over wood-based sheathing, stucco assemblies generally require two layers of water-resistive barrier, because fresh stucco bonds to and can compromise the first layer, so the second layer maintains a continuous drainage plane. One layer, no barrier, and an interior-only vapor barrier do not meet the two-layer stucco requirement.
Law Reference: 2025 CA Residential Code §R703.6.3Practice all 700 questions free — no signup required.
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