Bricks, Masonry, Asphalt and Concrete - Stucco Fuzz

I’m a handyman and every two or three years my neighbor calls on me to repair his stucco walls. There are some horizontal crack from 1 to 2 feet above grade and the stucco crumbles and falls off around them. After scraping and wire brushing and spraying with bleach, there is still a mold/fungus/whatever that appears within a day. It is white, fuzzy, looks like fur about ¼ inch long. I’m in southern California.

Any idea what this stuff is and if there is a better treatment for it than bleach?

It may be efflorescence, the deposition of chemical salts formed by the evaporation of moisture moving through a masonry surface, especially mortar joints in brick walls. A big part of stopping it is to ventilate the enclosed space or seal it to keep moisture out of it. If this is a dirt crawlspace floor, 6 mil plastic is normally used for this.

This will brush off, but returns due to the transpiration of the moisture through the mortar and the stucco. It may be necessary to tuckpoint this area as well as eliminating the moisture.

Hope this helps.

"I’m a handyman and every two or three years my neighbor calls on me to repair his stucco walls. There are some horizontal crack from 1 to 2 feet above grade and the stucco crumbles and falls off around them. After scraping and wire brushing and spraying with bleach, there is still a mold/fungus/whatever that appears within a day. It is white, fuzzy, looks like fur about ¼ inch long. I’m in southern California.

Any idea what this stuff is and if there is a better treatment for it than bleach?"


While this stuff "might" be effloresence, effloresence is very unlikley on a stucco surface.

For effloresence to form, one needs almost a constant and chronic cource of water leakage.

Effloresence is mineral salt that gets deposited on one side of the surface of a masonry wall when water seeps thru that wall and dissolves then crystalizes these dissolved salts.

If this "fuzz" is effloresence, it indicates and even bigger problem with stucco, that of a major water leak at the top of a stucco wall which cause water to flow behind it and out near the bottom.

More at stake than just removing the fuzz.

Have to fix the water infiltration.