Removing Mold and Stains from Stucco

Spraying a stucco wall with a pressure washer.
  • 2-4 hours
  • Beginner
  • 20-50
What You'll Need
Power washer
Hose including spray attachment
Protective face mask
Large sponge
Scrub brush
Bleach-free mold remover
Liquid detergent
Paint stir stick
Pump sprayer
Rubber gloves
Protective goggles

Homes with stucco exteriors are typically found in areas where it’s often warm and humid. This type of climate can become a breeding ground for mold growth. Stucco exterior walls are generally made from cement plaster. This porous material often absorbs stains caused by mold and mildew. Mold often has a brown or black hue to it but can also develop as orange and red spots. Cleaning mold from your stucco exterior is a rather simple process that can be completed in an afternoon. You can remove these stains by following some simple steps.

Step 1 - Prep

Read the instructions provided by the manufacturer of the mold remover product you have. Follow the directions carefully. Put on your protective goggles, face mask, and rubber gloves to prevent any chance of getting mold particles on your skin or breathing them into your lungs.

Step 2 - Rinse the Stucco

Use your garden hose to rinse any debris and residue from the stucco. Attach the sprayer to the hose and turn on the water. Begin at the top of each wall and work your way down as you rinse off all of the dirt from the surface.

Step 3 - Mix the Remover

Pour the mold remover into the bucket. If the manufacturer recommends, add water to the remover to decrease the concentration. Use a paint stir stick to combine the liquids into one mixture. Be sure to stir gently so that none of the liquid sprays out over the bucket.

You can make your own mold remover solution with dish soap and Borax. Fill your bucket with two gallons of hot water. Add ½ cup of borax and two tablespoons of liquid detergent to the water. Stir until the solution is combined.

Step 4 - Apply the Remover to the Stucco

Immerse your sponge into the mold removal mixture. Remove the sponge and squeeze out any excess liquid. Rub the sponge over a small area of mold. Place the sponge back into the mixture and continue applying it to small areas of mold on the exterior walls. Continue until the mold removal solution has been applied to all of the areas on the wall. For spots that are higher up on the walls, use a ladder to get to them. Be sure to secure the ladder properly to prevent any falls. If possible, have a friend or family member with you to hold the ladder in place. Allow the mixture to remain on the stucco for about 30 minutes.

Use your soft bristle cleaning brush to scrub the stain from the stucco. Be careful not to apply too much pressure to cause damage to the surface of the walls

Note: If you would prefer not to climb a ladder to get to areas that are higher on your walls, consider using a pump sprayer to apply the mold removal solution. These devices are available in several sizes. Visit your local hardware store and speak with a representative on the best size sprayer for your situation. Remove the lid from the sprayer tank. Carefully pour the solution into the pump sprayer. Replace the lid and ensure that it is secured tightly. Spray the mold areas making sure to apply extra solution on heavy stains.

Step 5 - Spray off the Remover

Remove the spray attachment from your garden hose and attach the power washer in its place. Connect the power washer cord to an electrical outlet. If necessary, use an extension cord to reach all sections of the walls with mold stains. Be sure to use an extension cord that is certified for outside use with a power washer device.

Turn on the water tap connected to your garden hose. Make sure the water is flowing at full force. Turn on the power washer. Point the end of the power washer away from the house and from any pets or people. Gently squeeze the wand trigger to ensure that it is working properly. Point the sprayer toward the stucco wall, beginning at the area closest to the roof. Move the sprayer in a horizontal motion across the wall. Slowly spray the wall from the top to the bottom. Stop in difficult areas and apply extra time on these spots. Once all of the mold stains have been removed from the stucco, allow the exterior wall surfaces to dry completely. This should take about 24 hours.

Step 6 - Prevention

To prevent mold and mildew from returning, speak with a professional about having fog coating cement paint applied to the stucco walls. This product comes in a powder format that is mixed on location with clean water. The paint is then applied to the stucco surface with a sprayer in order to achieve an even and uniform coverage. You can find a local exterior painting company that will be able to provide you with advice on protecting your stucco walls.