Protect Your Home

Mildew makes even a clean exterior surface look dingy and dirty. And, if left untreated, mildew can damage painted surfaces. In this brochure, you'll learn how to spot mildew, how to get rid of it, and how to inhibit its reappearance on your home.

What Is Mildew?

Mildew is a fungus that grows on warm, damp surfaces. Soap and water won't remove it, but bleach will. If your home's paint seems dirty even after you've washed the surface with water and detergent, suspect mildew.

To verify that a dark discoloration is mildew, first brush the area with a solution of water and detergent, then rinse. Put a few drops of household bleach on the surface, wait a few minutes, then rinse with water. If the discoloration bleaches away, you have mildew. You should act right away to bring the problem under control.

Why Mildew Forms

You'll fight mildew better if you understand a little about how this pest chooses its place of residence. Mildew, like other fungi, prefers warm, damp surfaces. It will survive on almost any organic material, even paint.

Warm and humid climates, like the American south, foster mildew growth. Dry, western climates are less hospitable. Seasonal factors play a role too. Mildew is less able to grow during cold periods. When summer arrives, however, growth may spurt suddenly.

Mildew is also more likely to form on the north side of your house. That's because this side remains in shade most of the day and is more likely to remain damp from dew or rain.

With these facts on mind, you are better prepared to spot mildew early, before it can get a foothold on your house. And the earlier you spot mildew, the less work you'll have removing it.

Removing Mildew

Always remove mildew before you repaint your home. Otherwise, you'll be covering up your problem-but only for a short time. The mildew will soon show through your new paint job.

It's also a good idea to remove mildew even if you aren't going to repaint. Mildew looks bad and lowers the value of your home in the eyes of prospective buyers. Mildew also is capable of ruining the surface it grows on.

To remove your mildew problem completely, follow this simple three-step process.

1.  Start with a good cleaning of the mildewed surface. Thoroughly scrub the surface with a mild household detergent solution and a long-handled brush used for washing cars. Rinse completely with a hose.

2.  Next, use a medium-soft brush and a solution of one quart of household bleach to three quarts of water to scrub down the surface. (Caution: Do not add detergents or ammonia to the bleach/water mixture. Be sure to wear rubber gloves, long sleeves, and eye protection to guard against splashes.) Let this solution remain on the siding for several minutes.

3. Then rinse the surface thoroughly with a hose and allow to dry.

If you will be repainting, allow the surface to dry before you begin.

Keeping Mildew At Bay

The best way to inhibit mildew growth is to keep surfaces dry. In most instances, you don't have much control over your home's exterior, but you can take several steps if mildew is a recurring problem:

-Trim bushes close to the house to allow air to circulate across surfaces.

-Trim trees that provide shade all day long.

-Don't seal plastic film over exterior window trim. Moisture leaking through the window may condense on the film and create damp conditions that promote mildew growth.

Choose paints and stains formulated to resist mildew growth. When applied to mildew-free surfaces, these products inhibit the growth of mildew.

New wood that has been exposed to the elements may already have mildew growing on it. If conditions have been favorable to mildew growth, treat the wood with the bleach solution described inside before you begin painting. Once the surface is completely dry, coat with primer and follow with a topcoat of paint. By choosing quality products, you know you have the best protection for your most valuable investment: your home.

Q:  What is mildew?
A:  Mildew is a fungus always present in the air. It feeds on organic matter, such as wood, leather, and paint. Under the right conditions-warmth and dampness-it will grow just about anywhere.

Q:  What types of cleaners can I use to remove mildew?
A:   Try using a solution of one quart household bleach in three quarts water. Apply the solution to the area with mildew and then rinse off with water. Never add detergents or ammonia to the bleach/water solution. Always protect your skin and eyes against splashes.

Q:  Can mildew be permanently prevented?
A:   No. Paints can be formulated to inhibit mildew growth, but under some conditions, mildew will eventually reappear on any type of paint.

Q:  Can't I just paint over mildew?
A:   No. Mildew left on a surface continues to grow even if painted over. Eventually, the growth will break through the film of new paint.

Q:  Do some colors resist mildew more than others?
A:   Not really, but it may seem that way. Dark colors tend to minimize the visibility of mildew, which also is a dark shade. But, because dark colors are more likely to dry slowly and remain tacky longer when freshly painted (making them more susceptible to mildew) you may want to avoid them.

Q:  I'm looking for some advice on painting exterior wood trim. I still think oil is the best coating to use, but I'm noticing that more and more other contractors say latex is the way to go. Any comments?
A:   Well, you could go with oil material and watch it go running down onto the body of the structure. Many oil-based materials develop a chalk face that gets washed onto surfaces, where it forms an unsightly discoloration and can be difficult to remove. This process takes 12-24 months, depending on the material, film build, color, sunlight exposure, and other environmental conditions. This is not going to make for a happy customer, nor repeat business for your company. (As you might guess, I'm coming down on the side of latex.)

Another concern I have with alkyd materials is how hard and brittle they become. This shortens their service life. Wood has a tendency to expand and contract as weather conditions change, which puts much stress on the coating. At this point, cracking and peeling can be a problem with alkyds.

Also, oil-based materials do not breathe as well as their latex counterparts. Moisture builds up behind the film and is drawn out by the sun. This force can cause non-breathing materials to lose adhesion. Naturally, how the trim looks is very important to a homeowner. The chemical makeup of latex materials allows them to hold their color and gloss far better than oil-based materials. The popular dark colors of today benefit from this attribute. Thus, your customer will be happier longer and your reputation remains intact.