Mold or mildew is a series of black, white, or grey colored patches that appear on walls, drywall, and wood. Can you cover these patches by painting them?
You can paint over mold and cover those areas. But, it is a temporary fix. Mold is an organism that thrives where there is moisture. So, if there’s still moisture in your walls or furniture, mold will grow again because the paint won’t prevent it.
So, the paint will just cover it, but won’t fix or prevent it.
Do You Need To Remove Mold Before Painting?
It’s recommended to remove the mold before painting. If you don’t, you will run into problems before and after doing it.
The first problem you’ll experience is poor paint adhesion. Since mold grows where there is moisture, it means that the surface where you have will paint is wet. Also, mold has a moist texture, so the paint will not stick well over its moist (wet) texture.
Oil-based paints especially won’t stick over it since they won’t perform well over wet surfaces. This will lead to a sticky finish.
The finish will also be affected by stains, especially if you use a light color shade, such as white yellow. Since there’s moisture under the finish, the moisture underneath will bleed through and cause brown patches.
It’s also difficult to seal a finish that has been affected by moisture or mold because the sealant will be also affected by stains na moisture. So, if you use a clear sealant, the finish will look bad. It can also cause it to crack, bubble and peel.
Does Painting Stop It?
Painting over mold doesn’t stop it from growing, it will still continue to grow. This is because mold is a fungus that grows anywhere there is moisture.
So, if mold appears on your walls or furniture, it’s because the surface is constantly exposed to high moisture content. This could be a result of a rooftop leak, damaged plumbing pipes, or exposure to rainfall. If you don’t fix these problems, paint won’t fix or stop mold.
Mold is more common on outdoor objects since these items are usually exposed to rainfall and cool air. Since mold is a living organism (fungi), water and air will make it thrive outdoors. So regardless of the number of coats that you apply, it will still grow because you have not addressed the main problem. You only masked (covered) the problem.
However, there are paints advertised as “Mold-killing”. These paints are formulated with fungicides to kill the mold and stop it from growing. But after a while, such paints will develop mold if the surface is still exposed to high moisture content.
How To Paint Over Mold?
Painting over mold isn’t hard, but you need the right guidance and tools.
Here are the tools you need:
- A bottle of bleach or vinegar
- A bucket of water
- A pair of gloves
- A scrubbing brush or scraper
- A respirator mask
- Eye protection
- A gallon of mold-resistant paint primer
- A gallon of paint
- A sealant or top coat (optional)
Now, let’s get to work.
1. Fix The Mold Source
Usually, any item that has suffered mold infestation will be damaged. If it’s a piece of furniture, the wood may have developed rot. If it’s a wall, it would be stained and weak. So you’ll need to repair the item first. You’ll also need to patch, seal, and repair leaks or anything causing it to grow.
2. Remove The Mold
Next, remove as much mold from the surface as you can.
To do so:
- Wear safety gear.
- Use a scrape or brush.
- Place a large drop sheet under the floor.
- Scrape it off.
3. Spray and Clean
To do this, fill a spray bottle with vinegar and spray the affected areas. Ensure to cover the entire area with vinegar. You can also use bleach or household fungicide.
Also, if you are working on a porous material like drywall, wood, and the likes, don’t spray the vinegar on the item. This is because these materials will easily suck the vinegar. In large quantities, the vinegar can damage wood, plaster, or drywall. Instead, soak a rag in vinegar and use the damp rag to wipe the affected surface.
If there’s a water leak, broken pipe, or something else that is exposing the surface to moisture fix it. If you don’t, mold will still cover wether you paint over it or not. So, fix the main problem (cause) first.
4. Apply Mold-Resistant Primer
Mold-resistant primer helps to prevent mold from growing on a surface. You’ll need 2-3 light coats of it for proper coverage. Ensure to allow each coat to dry before re-coating.
5. Apply a Few Coats Of Paint
To apply paint, use a roller, brush, or sprayer to apply 3 coats. Wait until one coat dries before applying the next one.
6. Seal The Finish (Optional)
Optionally, you can seal the finish with waterproof sealant. While the mold-resistant primer prevents mold from growing beneath the finish, the sealant will prevent water from penetrating the finish. It’s like a double protection.
You can use polyurethane, spar varnish, or lacquer as sealants.
Mold-killing primer does work but not in the way most people think while using it. They are designed to stop the growth of mold on a surface.
They are usually a preventive measure against mold growth. The paint is usually incapable of destroying large blotches of mold or mildew on a surface.
Since they are only designed to prevent fungi grow, they will cover it at first, but after a while, the mildew will still grow. So, you should use these paints only after you have cleaned (removed) mold with vinegar.
Generally, mold-killing paints aren’t known for their durability, they aren’t built with additives that give them durability. The additives in the are focused on preventing mildew growth. So, they won’t last more than 5 years.
This is why it is advised to seal them after applying them. Zinsser mold-killing primer states to apply a top coat within 72 hours for maximum protection.
You can paint over mold-killing primer as it is designed to be an undercoat and not a top coat. So you need to apply a top coat over it. Though you can leave it as the top coat, you wouldn’t get as good a finish.
Can Mold Bleed Through Paint?
Mold will bleed through the finish if you don’t remove it before applying the paint. This is because mold has high moisture content.
Also, the organism reproduces by traveling as light moist spores. These spores can easily sift from underneath the finish causing bleed-through of moisture and stains. The bleed-through is common with water-based paints since they use water as their solvent, and water is a necessity for the mold to thrive.
But, mold will not sift through moisture-resistant primer or paint since they are formulated with mold-control additives like fungicides to prevent its growth.
In summary, you can paint over mold, but only after you remove it and fix the problem that caused it to grow. If you paint directly over it, the mildew will bleed-through the finish and stain it.
It’s recommended to remove mildew using vinegar.
Tony is a professional painter and an author of DIY Geeks. Tony has completed over 1,000 painting projects for his clients. It's safe to say he knows what he Is talking about,