Wash outdoor stucco with a low-pressure power cleaner using a cleaning solution made up of a dishwashing detergent, 1 cup of borax, 1 cup of washing soda and 2 gallons of hot water.
Position the water nozzle no more than 36 inches from the stucco wall but always maintain a 1-foot distance between the washer nozzle and the wall to protect the stucco’s surface.
Move the water sprayer evenly over the surface rather than in concentrated bursts. Start from the bottom and work upward, moving the nozzle from side to side. Rinse the wall thoroughly using a garden hose after pressure washing.
Remove any remaining smoke stains with sugar soap powder -- 3.5 ounces of powder to 1.05 gallons. Alternatively, try bicarbonate of soda mixed with household bleach.
Apply the cleaning solution to the surface of the stucco with a brush and scrub it with a scouring cleanser. Rinse the wall thoroughly after scrubbing it. You can also use this cleaning solution on indoor stucco.