CSLB C-33 Painting & DecoratingSurface PreparationHard
A painting contractor is preparing a large exterior stucco wall for repainting. The wall has numerous small, non-structural cracks (less than 1/16 inch wide) that are stable. Which repair material is generally recommended for filling these cracks to ensure a durable and aesthetically pleasing finish?
- ARigid cementitious patching compound.
- BNon-sag polyurethane sealant.
- CAcrylic elastomeric caulk or filler.
- DEpoxy-based crack injection system.
Show answer & explanationAnswer & explanation
Correct answer: C. Acrylic elastomeric caulk or filler.
For small, non-structural, stable cracks in stucco, an acrylic elastomeric caulk or filler is the best choice. Its flexibility allows it to move with the stucco, preventing recracking, and it is paintable. Rigid cementitious compounds can recrack. Polyurethane is good for larger, moving joints but often overkill and harder to tool for fine cracks. Epoxy is for structural cracks.
Why the other options are wrong
- A. Rigid cementitious patching compounds will not accommodate the natural movement of stucco and are prone to recracking in small, non-structural cracks.
- B. Non-sag polyurethane sealants are effective for larger, more active joints but can be more difficult to tool smoothly for small cracks and are often an over-engineered solution.
- D. Epoxy-based crack injection systems are designed for structural cracks in concrete or masonry and are not appropriate for small, non-structural stucco cracks.
Stucco Hairline Crack Repair
Small, stable cracks in stucco are best repaired with flexible, paintable acrylic elastomeric caulk or filler to accommodate movement and prevent recracking.
- Stucco is a dynamic surface.
- Flexibility prevents recracking.
- Elastomeric products are designed for movement.
Memory trick: Stucco's small splits need flexible fills, not rigid cement's ills.