Painting a Block Wall and Sealing Efflorescence

By the time a block wall has been scrubbed, the white crust that came back after the last paint job is already forming again at the base of the first course. The salt deposit is the main thing to deal with before any painting begins, as the notes at painting torrance ca dine out somalia describe. A backyard wall in Torrance, CA drinks moisture from the soil and from the marine air, and it carries minerals to the surface as the water leaves.

What the white powder is

Efflorescence is mineral salt that dissolves in water inside the block and stays behind when the water evaporates at the face. Near the Pacific Ocean the air adds its own salt, and a wall beside a planter or sprinkler head wicks even more moisture. Paint rolled over the crust bonds to powder, not block, and it lifts off in patches within a year. The crust has to be removed first.

Wire brush, rinse and dry

A stiff wire brush takes off the loose deposit, and a rinse takes off the dust. Heavy buildup gets a masonry cleaner, rinsed well, because leftover cleaner leaves its own residue. Then the wall must dry. A block wall holds water deep in the cores, so a crew waits for a stretch of dry days and checks the base of the wall, where it stays wet longest. Patching comes next: hairline cracks and chipped corners are filled with a masonry patching compound and sanded flush.

Masonry sealer and block filler

Raw block is porous, and it will swallow topcoat until the pores are closed. A masonry sealer or an acrylic primer goes on first to lock in remaining dust and give the paint something to grab. Where the face is rough and pitted, a block filler is worked in with a heavy roller or a brush to close the pinholes, which cuts the number of coats and gives a more even sheen. Skipping this step means three coats of paint to do what one coat of filler does.

Roller nap and coating choice

A thick nap, three quarters of an inch or more, pushes paint into the texture of the block. A short nap leaves bare pits. An acrylic latex made for masonry breathes enough to let trapped vapor out, and a flat or low sheen hides the surface variation better than satin does. A sprayer speeds up long runs, but the paint still gets back-rolled so it fills the face rather than sitting on the high spots.

Why the base keeps failing

The bottom courses sit in splash and soil moisture, and they fail first. Raising the soil away from the block, redirecting a sprinkler, and sealing the wall base with a waterproof masonry coating slows the salt cycle. The wall will never be fully dry, but a coat applied over a clean, dry, sealed surface lasts several seasons longer than one rolled over salt.