By: Licensed Mold Assessor Brad Fishbein
February 4, 2023
Mold growing on drywall can be more dangerous than any other type of building material.
Drywall is cellulose based and has the ability to produce black mold more than other types of wall coverings such as plaster which is lime based.
Can you paint over mold on drywall? More specifically, can you paint over black mold on drywall?
There are certain scenarios where mold can be sealed by painting over it.
In this article we will explore when you can paint over mold on drywall and when it has to be removed.
Mold grows on drywall when it attaches itself to the building material after it’s been wet. People tend to think that only a leak can cause the walls to get wet but that is not the case. There are other times where walls can get wet without a large-scale “leak”.
Drywall can be painted over when there is surface mold only and not using the walls as food.
These are a few situations where mold can be painted over:
When cold air is combined with hot/humid air a dew point is reached and it can cause condensation. So if your air conditioning vents are not flush against the drywall on the ceiling or walls, cold air can escape the surrounding areas creating condensation on the drywall.
Also when you have an HVAC register that is too close to a light fixture, the heat from the light in combination with the cold air from the air conditioning can create condensation that leads to mold on the ceiling or wall.
In this scenario, the mold is superficial and is not producing mycotoxins. It is often referred to as mildew. Mildew on the drywall can be painted over.
Painting over mold on a shower ceiling is not a rule of thumb but in most cases it can be performed.
Showers create steam which is moisture. If the ventilation fan isn’t used or there is a vent in the bathroom condensation can easily build up on the ceiling leading to mold growth. This is especially true if latex paint is used.
In most cases, the ceiling in the shower can be painted over however, it must be ensured that the mold is not caused by a leak from the area above because then it will NOT be just surface mold. Mold will be on the backside of the drywall.
When mold is on drywall behind an air conditioning unit, it’s usually caused because the air handler is too close to the drywall. The cold air is creating condensation leading to surface mold. This is a very common occurrence in Garages or basements where there is high humidity.
The air conditioner should be moved further away from the wall but the good news is, that there is a good chance it is surface mold.
Drywall cannot be painted over when it has been wet for an extended period. Drywall that holds moisture content above 20% and is in a location where humidity is above 60% runs the chance for mold that produces mycotoxins to grow on the drywall.
If drywall has been wet for a period of over 24 hours, the drywall should not be painted over and should be removed.
The moldy walls should also be removed by a licensed mold professional because as stated above, black mold tends to grow on drywall easier than any other type of building material.
Once it’s been established that you can paint on the mold over drywall, you shouldn’t just use regular paint.
A special kind of anti-microbial paint should be used to encapsulate the mold. Mold killing paint on drywall will ensure that the spores don’t become airborne. There are paints used that do not have Volatile Organic Compounds (VOCs) and should be used if available.
A regular brush will do the job just fine. Multiple coats should be applied if needed.
Mold tends to grow on oil-based paints more than any others because it acts as a food source for mold and mildew.
Whether or not drywall can be painted over should be a judgment call based on how much water damage is present.
Proper precautions should be taken if mold is painted over drywall including the use of rubber gloves, goggles and a mask with respiratory protection.
Meet the author: Brad Fishbein is an ACAC council-certified Microbial Investigator. In the fall of 2012, he became a Licensed Mold Assessor in the State of Florida through the Department of Business & Professional Regulation. Brad has helped homeowners with over 5,000 successfully completed Mold Inspections since 2009.