Stucco cracking on exterior walls — San Francisco, California

Cracks in exterior stucco range from harmless cosmetic hairline cracks (less than 1/16 inch) to structural warning signs. Hairline cracks are normal in stucco as it cures and responds to temperature changes — most homes with stucco develop them within 1–5 years. However, cracks wider than 1/8 inch, cracks that follow a stair-step pattern along mortar joints, or cracks that appear suddenly in clusters may indicate foundation settlement, water damage behind the stucco, or structural movement. The danger of any stucco crack is water intrusion: water enters the crack, soaks the building paper or lath underneath, and causes hidden rot, mold, and further cracking in a cycle that accelerates without repair. Cosmetic repair involves filling cracks with elastomeric caulk or stucco patching compound and repainting ($200–$600 for spot repairs). Larger cracks may require removing damaged sections, inspecting the substrate, re-lathing, and applying fresh stucco coats ($5–$15 per square foot). If cracks keep returning, the underlying cause — drainage, foundation settlement, or missing control joints — must be addressed.