Depending on the size of the area to be cleaned, the tools used for cleaning will vary: You can hand clean with a soft to medium bristle brush or shop broom to reach higher on the wall without needing a ladder for isolated surface spots, use a garden hose for a full wall, and pressure wash for an entire building and/or difficult to remove accumulations of dirt.
A good generic cleaning solution is 1-2 cups trisodium phosphate (TSP) detergent available at your local Home Depot or Lowes, and 1 gallon of warm water. Add 1/2 to 1 quart of bleach to remove algae (usually green stains on the surface of the finish) or mildew (the black stains that look like dirt). The bleach is necessary to kill the micro-organisms that create the algae or mildew, and you’ll want to let the cleaning solution sit on the wall surface for a few minutes (15 minutes is usually sufficient), prior to rinsing it off. If no bleach is used or if you don’t give it the wait-time between application and rinse, algae or mildew will re-occur. If you don’t have algae or mildew on the surface, then bleach isn’t necessary and the TSP detergent will get the job done with a little elbow grease and a light scrub.
Apply the TSP cleaning solution to the wall surface by brush or spray and allow to soak for a period of 15-20 minutes. For heavy deposits, lightly scrub the specific area with a soft medium bristle scrub brush. If you use a pressure washer, keep the pressure at approximately 200-500 psi. Keep the nozzle several feet from the surface of the wall and keep it moving – don’t hold it steady in a small area as the surface integrity of the finish can be destroyed with high pressure washing.
After the cleaning solution has soaked the surface, rinse the surface thoroughly with clean water and allow to dry. There are also some proprietary cleaners available, especially for dealing with algae and mildew, so READ THE LABEL AND FOLLOW THE MANUFACTURERS DIRECTIONS. Always check local regulatory requirements for disposal of cleaning solution and waste water.
Now, here are the DO NOT DOs for cleaning your stucco:
- DO NOT use solvent based cleaners – acetone, gasoline, ketones, mineral oils, or turpentine
- DO NOT use steam cleaning or other high temperature cleaning methods
- DO NOT use excessive scrubbing, stiff bristle brushes or wire brushes
- DO NOT use high pressure washing (in excess of 500 psi), or sandblasting
That’s pretty much the process for surface cleaning your stucco, and can often be accomplished on a weekend as a DIY project, depending on the size of the area to be cleaned and if you haven’t let it go for too long.