How can I prevent white stains from appearing on my stucco walls?
That unsightly “efflorescence” shows up when the sun dries everything off after one of our rare soaking rains or in spots where your sprinkler has sprayed water on your house over and over.
You can’t unbuild your house, but you can strip the stucco down to nearly new and take some preventive measures that could lessen the appearance of those efflorescent eyesores. Here are four steps to banish—or at least blunt—the fuzzy white blight:
- Use a power washer to remove dirt, loose paint and all signs of efflorescence from the walls. For tough spots, add some diluted trisodium phosphate (TSP; find it at any home store) to the power washer’s secondary pickup tube.
- Use an elastomeric compound to seal cracks in the stucco and a silicone-based caulk to close up gaps and cracks around windows, doors, plumbing pipes and other “holes” in the exterior walls that could let water drip behind the stucco. A caution: Do not paint elastomeric compound over your entire wall. It creates a seal that’s so tight it prevents the walls from “breathing,” so if water gets behind them, it can’t get out. Trapped water can cause problems beyond ugly white blotches on your stucco.
- Prime the walls with an alkali-resistant sealer like Dunn-Edwards Paints’ Eff-Stop, designed to help neutralize the efflorescence. Spray a liberal coat of 100 percent acrylic paint over the primer, and then painstakingly work the paint into the wall surface with a roller. If you don’t have a sprayer, use a roller alone, but slather on a lot of paint and press it into every tiny crevice in the wall. Spraying alone won’t do the job right.
- Keep moisture away from your freshly primed and painted stucco. Move sprinklers away from the house or you’ll find yourself with the same problems despite the effort you made to prevent them.
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