Although stucco, like other masonry surfaces, can be painted this is neither the best nor the most economical way to change color. Over time, paint tends to fade, chip and peel away from stucco walls.
Usually, spotty or “blotchy” stucco color is a result of variations in the thickness of the cement “base coat” beneath the stucco finish. Slightly thicker areas can retain moisture longer. This drying pattern can cause the slower-drying areas to appear darker. Typically, this happens more during winter months, and on shaded surfaces.
Locate the Manufacturers Color Code number from your builder or applicator. Remember, stucco colors darken slightly as they age. Be sure to consider this when purchasing new stucco to match an existing finish. You might need a slightly darker shade of the same color for older stucco. We recommend conducting a color test to compare the new color with the old before applying stucco to the entire addition.
Most stucco colors darken slightly over time because they contain natural all-mineral ingredients. Unlike painted surfaces that have only a thin layer of paint that can fade, chip and/or peel, stucco color is “integral.” This means stucco color extends through the entire stucco layer instead of only on the surface. Properly maintained exterior stucco can remain attractive for many years with only minimal changes. However, exposure to dust, dirt and air pollution over time can slightly change its color.
This sounds like colonies of mildew. These microscopic organisms are part of the natural life cycle of organic matter, including decay and composting of landscaping plants and mulches. Excessive moisture in flowerbeds, shrubs, mulch and other organic materials creates ideal growing conditions for these organisms. Prevent, or minimize, it by eliminating the excess moisture: be sure irrigation systems are not directed against walls and keep plants trimmed back to allow ample light and air circulation. Remove these discolorations from stucco surfaces with household bleach followed by a thorough flush with clear water.
This is probably “efflorescence,” also known as “alkali.” Efflorescence or alkali consists of salts leached from cement-based materials when exposed to excessive, saturating moisture. It appears as a whitish powdery “bloom” on the surface of the wall. A wash down with white vinegar or another approved dilute acid solution, followed by a thorough flush with clear water will usually remove efflorescence. Taking care to direct sprinklers, irrigation systems or other sources of water away from stucco walls will help prevent it. REMEMBER: always keep acids and other chemicals away from children, and ALWAYS use the proper safety equipment – including eye protection – when working with any hazardous substance!
As stucco cures some of the water it contains evaporates. This causes the stucco to shrink slightly. As it shrinks, small cracks called “check cracking” might appear. Applying stucco finishes in hot, dry weather could contribute to check cracking in stucco. During periods of hot dry weather conditions, a light spray (mist) of clean water is recommended over the stucco finish. Some check cracking in stucco is normal.