Concrete Masonry Units / Concrete Block
New Work: #470 Block Filler must be worked into surface pores while wet with a long nap roller cover, and must be back rolled when spray applied. The pH of the blocks must be below 10 and all efflorescence must be removed prior to painting.
Efflorescence can be removed with a solution of muratic acid, or by using a wire brush, high pressure cleaning, or sandblasting. Muratic acid must be neutralized with water prior to painting.
Previously painted: Remove all dirt, chalk, mildew, efflorescence, loose or peeling paint and other surface contaminants by power washing, scraping, or sanding. Patch holes and other surface defects with proper patching materials. Treat mildew with a bleach solution and rinse thoroughly. Patched areas should be primed before finish coating. Replace caulk that may be missing or cracking.