How to Kill Mold in Plaster

Edriaan Koening

Simply spraying products such as disinfectants, biocides and cleaners on plaster surfaces might kill mold spores and remove their ability to reproduce. However, these products will not remove the spores, which can create a health risk even after they die.

Because of the semi-porous texture of plaster, mold does not destroy its structure. After you kill the mold and clean the plaster, you usually will not need to replace it.


Identify the moisture problem that causes mold growth and fix it. Otherwise, mold will grow again even after you kill and remove it. Consider hiring a mold consultant or contractor if mold grows in an area that is greater than 30 square feet.


Don't take part in treating or removing mold if you are immuno-suppressed or have allergies, asthma or respiratory diseases.

  1. Wear a breathing mask or respirator to protect your nose and mouth when you handle moldy materials. Also wear gloves, eye protection, a long-sleeve shirt and long pants. During a mold treatment or removal project, the mold count can amount to 10 to 1,000 times the normal count. Inhaling these mold cells can lead to health problems such as allergic illness, asthma, respiratory infection and poisoning.

  2. Mix 1 cup of dishwashing detergent and 1 gallon of water. Pour the solution in a spray bottle and spray the moldy plaster with the solution. This prevents mold dust and spores from getting into the air.

  3. Mix 1 cup of a soap or detergent that contains no ammonia and 1 gallon of hot water. Spray the solution onto moldy plaster surfaces and use a brush to scrub the surfaces.

  4. Rinse the affected plaster surfaces with water to remove the detergent residue. If available, use a wet-dry vacuum to absorb the excess water.

  5. Mix 1/4 to 1 1/2 cups of liquid chlorine bleach and 1 gallon of water. Spray the solution onto affected surfaces and leave it to air dry for six to eight hours. Open any windows and doors to increase ventilation in the treated area.

  6. Place a fan or a dehumidifier near the treated surfaces to help them dry out quicker. Moist surfaces encourage mold growth to recur.