Mark Roemer image of a moldy wall

Dealing with Mold Growth on Plaster Walls

I, Mark Roemer Oakland, believe that unless the mold problem is too severe and has penetrated deep into the walls to cause structural issues, it is easy to clean and get rid of. You don’t even need to use any toxic chemicals for that. Let’s figure out how you can deal with mold growth on plaster walls.

The Details

1. Identify the cause of the mold – Before you start cleaning and disinfecting molded walls, take your time to identify the cause of the mold. Identifying the cause of the mold lets you take preventive actions against it so that you can prevent mold growth in the future. Most types of mold growth happen due to excess moisture levels.

When you have a leaky pipe or lack proper ventilation in the room, mold has the perfect opportunity to grow and spread. It will spread rapidly since it’s a fungi colony that is asexual in nature. That’s why it’s important to pin down the cause of the mold growth and fix leaky pipes, add ventilation ducts or introduce a dehumidifier in the room to address the cause.

2. Prep your room and start cleaning the walls – Mold is a living fungi colony. Apart from damaging your home, it can also cause respiratory issues and other health problems. That’s why you should equip yourself with proper safety gear like rubber gloves, masks, and safety glasses before you start cleaning the mold.

Open the windows, close the door and start clearing the room. Keep a fan directing air out the window to remove all mold spores outside. Remove fabrics, furniture pieces, and electrical equipment that was near the walls affected by the mold and put them under the sun for a few hours to kill off residual spores with sunlight.

After you’ve emptied out the room, turn off the air conditioner or the HVAC system to prevent mold from spreading to other parts of your home. Use plastic sheets to cover the floors and other structures. Now, soak a damp sponge in dishwashing liquid and clean the molded area. After you’re done cleaning and scrubbing the mold off the wall, use warm water to rinse the entire room including the ceiling and walls with clean rags to collect and dispose of airborne mold that may have settled on those surfaces. 

3. Remove mold with vinegar and baking soda – After you’re done cleaning the mold, it is time to disinfect and kill the spores. Vinegar and baking soda are household items that do a good job of removing mold. Research shows that vinegar can penetrate the wall and kill more than 80 percent of mold spores.

Pour white vinegar into a spray bottle and apply it to the entire wall. Let it rest and penetrate into the wall for an hour and wipe it clean with a damp sponge soaked in warm water. Next,  you need to scrub the mold off the walls with a baking soda solution. Baking soda is a natural disinfectant and deodorizer. 

Mix a teaspoon of baking soda in a spray bottle with two cups of water. Spray it on the walls and scrub off the mold with a brush. Follow-up by rinsing the area with warm water. Baking soda would disinfect the walls and also remove the musty smell. You can do another round of vinegar and baking soda cleaning if you’re not satisfied.

4. Removing mold with Borax – You can also use Borax to remove mold. Mix one cup into a gallon of hot water and shake it well. After the borax is dissolved, pour the borax solution into a spray bottle and spray it on the molded area. Use a scrubbing brush to scrub off the mold. After that, allow the wall to dry off and follow up by rinsing it with warm water. This should kill off the mold and prevent it from returning if the cause of mold growth has been addressed.

5. Removing mold with Tea tree oil – Tea Tree essential oil is both antibacterial and antifungal in nature. It is one of the greenest ways to get rid of mold growth. However, it’s more expensive and not as potent as the other solutions mentioned here. If you decide to use tea tree oil to remove mold, prepare yourself to do a lot of wiping for a long time.

Fill up a spray bottle with a few teaspoons of tea tree oil and two cups of water and apply it to the walls. Let it rest for an hour or two and wipe it off with a clean cloth. You may need to repeat this process several times for satisfactory results.

6. Hydrogen Peroxide – If the mold problem is severe and has penetrated deep into the plaster, you need something more powerful like hydrogen peroxide. It’s an excellent disinfectant to kill mold and gets stronger when mixed with vinegar. While bleach is also a powerful mold killer, it may create toxic fumes when used on walls. On the other hand, hydrogen peroxide breaks down into moisture and oxygen after doing its job.

Pour three percent concentration of hydrogen peroxide into a spray bottle with half the amount of vinegar and spray on the affected area. Let it rest for around 20 minutes to get deep into the pores and kill all the mold. After that, scrub the mold off with a brush. If the mold problem is too severe, it may have already penetrated deep enough to weaken the underlying wood lathes in the wall. In that case, you’ll need to get your home inspected and repaired. If just the paint on the walls has been damaged, you need to repaint it all.    


I, Mark Roemer Oakland, suggest that you take your time identifying the cause of the mold and take actions to prevent that from happening again after you clean and disinfect the mold growth. Usually, controlling the moisture level in the room with a dehumidifier or proper ventilation prevents mold or mildew from growing on your walls.