Wondering what those black spots are on your wall and how they got there in the first place? It’s likely mildew, a common sign of excessive moisture around the home. In this guide, you’ll learn what mildew is, how it differs from mold, how to remove it and the Sherwin-Williams products you can use to prevent it from returning.

Mildew is a fungus variant that forms black, gray, green, or brown spots on a surface. It typically grows flat across a surface and is powdery to the touch. In spaces with a serious mildew problem, you may smell a musty, earthy or sour smell. If you’ve encountered any of these signs, test for mildew by applying a few drops of household bleach to the area; if it is bleached away, the discoloration is probably mildew; if it doesn’t disappear, it’s probably dirt.

Mold and mildew are often mentioned together or interchangeably, but there are notable differences between the two. Mildew is a type of mold, but it’s not as hazardous as mold. It grows in a flat pattern and is often considered powdery. Mold, on the other hand, grows into circular spores that are slimy or fuzzy. Mold can be green, red, black or blue, while mildew is often white, gray or light brown.

We’ve mentioned that mildew isn’t as harmful as mold, but how harmful is it? Mildew can cause mild to moderate allergic reactions, such as sneezing, runny nose, eye irritation, skin rash and headaches. In more severe cases, mildew can trigger breathing difficulty or asthma attacks.

Mildew is a symptom of an environment that’s too moist or receives little to no direct sunlight. It can form on interior and exterior surfaces such as walls, windowsills and ceilings.

If you find mildew in your home, you’ll need to take steps to remove it and prevent it in the future. Most importantly, don’t paint over mildew! Because mildew is a living organism, mildew will continue to grow. Painting over it can also create the perfect environment to worsen the problem, making proper removal much more challenging. 

A bleach/water mixture and vinegar are the two most common ways to remove mildew, but the surface from which you remove mildew can affect the best method. Because bleach can cause color damage, it’s best used to remove mildew from showers and plastic surfaces. If you plan to paint, use bleach to remove mildew from walls since color damage won’t matter.

Vinegar is the best solution for removing mildew from recently painted and wood surfaces. 

To remove mildew with bleach, you’ll need protective eyewear, protective clothing and waterproof gloves, as bleach is a corrosive chemical. Because mildew powder can be irritating if inhaled, a ventilated mask is also recommended.

1. Create a solution of one part liquid bleach and three parts water.
2. Apply the solution, scrub the mildewed area, and allow the solution to sit on the surface for 10 minutes.
3. Rinse thoroughly with water and allow the surface to dry before painting. 
    

If the bleach mixture comes in contact with your skin, quickly wash off the mixture and remember never to add detergents or ammonia to the bleach/water solution.

To remove mildew with vinegar, spray it directly on the mildew and allow it to sit for an hour before scrubbing the area and thoroughly rinsing it with water.

Now that you’ve removed all traces of mildew from your space, it’s time to prevent it from coming back. The easiest way to do this is to treat the cause. Control moisture levels with dehumidifiers and exhaust fans and ensure proper ventilation in damp areas. Maintaining an indoor humidity below 60% will help keep mildew from returning.

If mildew is the only problem in your space, repainting may not be necessary after cleaning the surface. However, you may need to repaint if you use bleach, which can cause color damage.

Whether repainting was a planned part of your mildew renewal process, choosing a paint inhibiting mildew growth is best. Luckily, Sherwin-Williams offers a variety of interior and exterior paint formulas to help.

Interior Paint Formulas to Prevent Mildew

• Premium Wall & Wood Primer ensures a smooth base for your walls and wood surfaces.
• SuperPaint Interior Acrylic with Air Purifying Technology features antimicrobial agents that inhibit mildew growth and can contribute to cleaner indoor air quality.
   

Exterior Paint Formulas to Prevent Mildew

• Multi-Purpose Latex Primer is an exceptionally durable primer that will withstand the elements.
• You can also jump right in with self-priming Duration® Exterior Acrylic Latex, which has a mildew-resistance coating. Use this formula in interior spaces as well!

If you need help choosing mildew-resistant paint or need to pick up protective gear, head to your neighborhood Sherwin-Williams! We’ll help you find a primer best suited for the condition of your walls and choose a color to complement your space.