How should concrete, masonry, or stucco surfaces be prepared before coating?

• A. Clean, repair defects, ensure dry, profile the surface if needed, and use appropriate primer.
• B. Sand heavily and apply topcoat.
• C. Paint directly after wet.
• D. Use only water-based cleaners.

Answer: (A)

Effective coating of concrete, masonry, or stucco starts with thorough surface preparation. Begin by cleaning to remove dirt, grease, oils, salts, and any loose material or old coatings so the new coat can properly bond to sound substrate. Next, repair all defects such as cracks, spalls, and loose or flaking areas so the surface is solid and uniform. Then verify the surface is dry and within the moisture limits recommended for the coating, since trapped moisture can cause peeling, blisters, or mold growth. If the surface is very smooth or highly porous, create a profile—the microscopic roughness that helps the coating grip—by light etching, wire brushing, or appropriate sanding. Finally, apply an appropriate primer designed for concrete, masonry, or stucco and compatible with the topcoat; the primer seals porosity, improves adhesion, and can block moisture or stains. Skipping these steps and sanding heavily, painting while the surface is wet, or cleaning with only water-based cleaners can lead to poor adhesion and premature failure.