Mildew or mold? How to know for sure.

Key tips to remember

  • Mildew and mold are both fungi, but mildew grows on the surface of a given material.
  • Mildew is relatively easy to remove with a good scrub brush and household cleaner.
  • Organize the garage or shed to keep essential tools handy.
  • Mold can cause respiratory problems, so best to let experts do mold remediation work.
Maintenance and Repairs

Suspicious dark stains around the inside or outside of your house are every homeowner’s nightmare. And the first step toward making those stains go away — and keeping them from returning — is determining whether you’re dealing with mildew or mold.

Unfortunately, mold and mildew stains look a lot alike. And while both are problematic in their own ways, mold is generally considered the more pressing health concern. You don’t want to mistake it for mildew. The treatment isn’t the same, and attempting to remove certain types of mold without adequate protective gear can expose you to serious respiratory irritants.

But how can you know for sure whether the stains you’ve discovered are mold or mildew? Keep reading for our tips!

Mildew vs. mold

Mildew is a type of fungus. It’s usually white or gray in color, and like most fungi, it grows in patches. It requires moisture and warm temperatures to survive, and it only grows on the surface of a given object. Mildew is most commonly found in bathrooms and other areas around the house that typically stay warm and damp.

One of the many not-so-great things about mildew is that it doesn’t discriminate when it comes to where it grows. Walls, grout, caulk, and even textiles like towels and shower curtains are potential targets. Have you ever forgotten a load of laundry in the washer for longer than you’d like to admit? (We all do it!) Well, that funky smell you notice when you open the washer is the beginning of mildew.

Yep, it’s pretty gross. But the good news is that mildew is mostly harmless (and not too terrible to remove), as long as you don’t let it hang around.

Mold, on the other hand, is more concerning. Mold is also a type of fungus that needs a warm and damp environment to grow, but certain types of mold can cause or exacerbate health problems in some people.

While mildew is pretty reliably either white or gray, mold can show up in a range of colors depending on the specific type of spore. Mold can also vary in appearance and texture, though the mold you’re most likely to find on walls and other structural parts of a house usually grows in spotty, fuzzy patches.

The biggest problem with mold is that certain types — usually referred to as “toxic” mold — can be hard to find and remove, and can cause serious respiratory problems, especially in people who are predisposed to asthma and other breathing difficulties.

Mildew is a true surface fungus and can be removed with a household cleaner, a scrub brush and some elbow grease. Mold, on the other hand, is much harder to remove. You might be able to scrub away the dark stain left by a patch of mold, but that doesn’t mean that the mold spores are gone.

If the environmental conditions remain the same, the spores are likely to grow back pretty quickly. In some cases, you’ll need to have the affected surface(s) removed altogether. And if you or anyone in your household has health problems, you shouldn’t make this a DIY project.

Removing moldy drywall, insulation or flooring without the protective gear the pros use is almost guaranteed to release mold spores into the air. Don’t take that chance! Let the pros handle the mold remediation work.

3 easy steps to prevent mildew and mold growth

1. Don’t let humid air hang around.

The best thing you can do to prevent mildew and mold growth is to keep all the rooms in your home from becoming too humid. Building materials like wood, drywall and flooring are not designed for damp indoor air, particularly for long periods of time.

That being said, don’t panic about the 20-minute-long steaming hot shower your teenager takes at least once per day. Those showers might do a number on your utility bills, but as long as your teen is using the bathroom vent fan during (and after!) their shower, the post-shower humidity shouldn’t pose too much of a problem.

The key here is the bathroom vent fan. It doesn’t remove humid air if it isn’t in use or if it isn’t vented properly. Unfortunately, a relatively common shortcut that some contractors make is to vent bathroom fans into the attic. All this does is transfer the warm, damp air from the bathroom to another space. And that space is where the mold and mildew will grow. Fungi like mildew and mold love roof trusses and insulation, so make absolutely certain that your bathroom vent fans direct their exhaust outdoors.

2. Keep the basement dry.

Basements, cellars and crawl spaces — especially those below ground — are notorious for being damp and musty. It’s hard to keep any below-grade space totally dry, but you have to try. If you have water intrusion problems, your first step should be talking to a foundation-repair or basement-waterproofing contractor. Water visibly puddling on the floor or dripping down the walls of your basement can indicate a larger problem that needs to be dealt with first.

A basement-waterproofing system might take care of the dampness issue, but if it doesn’t — or if your space is just a little musty and doesn’t need structural work — a dehumidifier is a must-have.

A dehumidifier is a device about the size of a single-drawer filing cabinet, and it pulls water out of the air in a given space. The water removed from the air goes into a holding tank, which you can then use to water plants.

Much like a portable air conditioner or heater, you’ll need to make sure you purchase the right-size dehumidifier for your basement or crawl space to ensure that you get the maximum benefit. Most dehumidifiers on the market today have a variety of settings, so there’s no risk that the water holding tank will overflow, or the dehumidifier will run constantly and waste electricity.

3. Stick to a regular cleaning schedule.

If you’re incredulous that anyone wouldn’t already have a set cleaning schedule, you can probably skip this part. For those of us who are perhaps a little less enamored of cleaning, here’s a really good reason to develop a routine: The more often you clean something (or even look at it), the more likely you are to catch mildew and mold before it becomes a serious problem.

Clean the grout in your bathroom before you notice any discoloration, and don’t let wet or damp towels crumple up in unventilated areas, like hampers or corners of rooms. If any spaces in your home are below-grade, don’t ignore odd smells or a change in air quality. If the basement starts to smell musty or the air feels damp to you, those issues need to be addressed.

Almost every homeowner cleans away a little mildew from time to time. And even mold isn’t a crisis, as long as you catch it early. But avoiding these problems altogether isn’t too difficult with a little attention to detail. Keep your house dry and clean, and mildew and mold will stay away.

Ready to make this year the year that you keep your house in awesome shape? Cinch Home Services is here to help! Check out our simple home protection plans, and then sign up for our newsletter and follow us on social media to stay in touch.


The information in this article is intended to provide guidance on the proper maintenance and care of systems and appliances in the home. Not all of the topics mentioned are covered by our home warranty or maintenance plans. Please review your home warranty contract carefully to understand your coverage.