How to Clean and Paint Stucco
Stucco is a traditional exterior building material noted for its durability, versatility, economy, and ease of application. You can take some steps to ensure the long life of stucco.
Step 1 - Repair
First of all, make sure your stucco is in good repair. Paint will fill hairline cracks. However, cracks from the width of a credit card up to 1/8 inch will require a brushable elastomeric sealant.
Wider movement cracks call for professional repair that may include raking the cracks and filling them with a urethane sealant system or other treatment. Movement cracks and other serious problems, such as loose framing, cannot be cured by patches and paint, so again be sure to seek professional assistance if that is the case with your stucco.
If stucco patching is performed, prevent cracking the repairs by not allowing the repair area to dry too quickly. Shade or even cover repairs in hot weather. When it's hot, it is a good idea to keep the newly stuccoed area damp, at about 90 percent humidity for 48 to 72 hours.
Do not repair stucco if the temperature will soon fall below 40 degrees Fahrenheit. Prior to painting patchwork, the moisture and pH levels must be at levels specified by the paint manufacturer. Perform repairs prior to cleaning to prevent water from entering the building.
Step 2 - Clean
Coatings require a clean, sound surface free from dust, chalk, mildew, grease, loose paint, and other contamination.
The most common method of cleaning is light pressure washing, possibly with a chemical cleaning agent. The object is to obtain a sound substrate without damaging the stucco.
If the surface is chalky, crumbly, or sandy after cleaning, a masonry surface conditioner may help consolidate the stucco.
Inspect flashing, such as over doors and windows, to ensure the sheet metal or plastic sheathing is securely in place.
As the last step in surface prep, caulk around windows, doors, flashing, exterior light fixtures, and other protrusions.
Step 3 - Repaint
A quality acrylic latex paint formulated for stucco or an elastomeric are the coatings of choice. Acrylic latex provides excellent protection unless some substrate problems or the need to protect against wind-driven rain make elastomeric a better choice. Elastomerics, for years the popular choice in coastal areas, are gaining popularity among owners in northern and interior locales because their heavier film build and elasticity provide the highest degree of protection possible.