Mold or Mildew: The Difference Between Mold and Mildew

Although the terms mold and mildew are sometimes used interchangeably, they are two distinctly different members of the fungus family. That said, there are a number of similarities between them as well as a few key differences. We look at how mold and mildew are similar and what sets them apart. Most importantly, we look at where they are most commonly found and how to treat them.

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What is Mold

Mold is a type of fungus that breaks down organic material in nature. Within your home or business, mold will grow on any cellulose-based material in the presence of moisture. Over time, it will break down walls, ceilings, and other materials in your property. It is most commonly found in areas with moist or humid conditions like kitchens, bathrooms, and basements.

Mold also poses a health risk and may cause allergy-like symptoms with regular exposure. Those prone to allergies, the very young, the elderly, and those with chronic illnesses, respiratory conditions, and immune deficiencies are more likely to experience severe symptoms.

Common Types of Mold

There are more than 100,000 types of mold and many of them may grow indoors if the conditions are right. The CDC recognizes four primary mold families that are common in homes. Despite begin reasonably uncommon, Stachybotrys chartarum often comes up in conversations about mold.

  • Cladosporium – One of the most common household molds, Cladosporium is usually a dusty, powdery substance that appears from olive-green to brown and black. It is among the most common molds because it can grow in colder than average temperatures.
  • PenicilliumPenicillium may appear blue, green, or black and commonly grows on leather, carpeting, drywall, mattresses, wallpaper, and upholstery.
  • Alternaria – Known for its large spores, Alternaria is found on carpeting and other textiles, dust, plant soil, window frames, and in showers.
  • Aspergillus – Common in warmer climates, Aspergillus prefers wetter conditions and higher humidity. It is especially common after untreated water damage.
  • Stachybotrys – Although much less common, the Stachybotrys family of molds is infamous. Often known as “toxic black mold”, it was incorrectly connected to the death of infants in the early 1990s. While it does pose a health risk, there is no definitive evidence that it is more dangerous than other molds.

What is Mildew

Mildew is also a naturally occurring fungus. While it does grow on organic material in the presence of moisture, it more common to plants. Within homes and businesses, it will grow on most flat, cellulose-based surfaces. It does break down organic material like mold, however, it works much slower.

Similarly to mold, mildew also poses a minor health risk. Despite this, the risk of mildew expose are much lower than that of mold. Common symptoms are very mild allergies. Because mildew decomposes material much slower and a has a significantly lower health risk than mold, it is much less of a concern.

Common Types of Mildew

Like mold, there are a large number of varieties of mildew. However, most mildews are classified in one of two categories.

  • Powdery Mildew – As the name would suggest, Powdery mildew looks like a white or grey powder. It is commonly found on flowering plants and some agricultural products in nature. Of the two classifications of mildew, it is more commonly found in homes and businesses.
  • Downy Mildew – Downy mildew is more common to agricultural products and is rarely found indoors. Typically it appears as a yellowish stain and slowly turns brown, but the appearance may vary depending on the material involved.

How Mildew and Mold Grow Inside Your Home

Mildew and mold both reproduce through spores, which are similar in structure to plant seeds. These spores exist all around us in the air, which allows mold and mildew to travel virtually anywhere.

Spores can enter your home through open doors and windows and even on your skin or clothes. While these spores can result in mildew or mold, they only pose a risk if the conditions are right for them to grow.

Requirements for Mildew and Mold Growth

  • Moisture – Mildew and mold both require a persistent source of moisture to grow.
  • Organic Materials – Mold and mildew both need a food source and most materials in your property are conducive if the other conditions are met.
  • Temperature – Mildew and mold prefer a consistent temperature between 70° F / 21° C and 90° F / 32° C. However, some strains may grow anywhere between 32° F / 0° C to 120° F / 49° C.
  • Light Levels – Although they don’t require complete darkness, mold and mildew prefer areas free of intense or direct sunlight and low UV levels.
  • Oxygen – With oxygen is a requirement for mildew and mold growth, even the most stagnant air provides the right conditions.
  • Time – With both mold and mildew require time to grow this is the one requirement with a moderate variance between them. Mold can grow in as little as 24 to 48 hours depending on the circumstances. Mildew, on the other hand, usually takes days or even weeks to grow.

How to Tell the Difference Between Mold and Mildew

Similarities Between Mold and Mildew

Since both mold and mildew are types of fungus, there are many similarities between them. In some cases, this can make distinguishing the two of them difficult. Mold and mildew both require a consistent source of moisture, an organic material, and the right temperature range to thrive.

Differences Between Mold and Mildew

There are two key differences between mold and mildew. First, mildew is almost always white or light grey. Whereas mold can be a variety of colors, including black, grey, blue, green, yellow, and pink. While some molds are white, appearance is also important.

Mildew usually grows on flat surfaces in even layers. In most cases, it will appear powdery or dusty. Mold on the other hand almost always appears fuzzy and in irregular layers. It may appear to grow on top of itself, rising off the surface. In extreme cases, mold may look like moss or even like plants.

Most Common Places For Mildew to Grow

Strictly speaking, mildew will grow anywhere with persistent moisture. That said, it is especially common in bathrooms. To a lesser extent, it is found in kitchens as well.

Bathrooms

Bathroom, and especially showers, are one of the most common places to find mildew. They are usually warm and wet, with a low amount of light most of the time. Your shower tile, washcloths, and many other items provide a food source for mildew.

Look for mildew around your bathtub and on your shower walls. It may be hard to differentiate from water spots, especially if you have hard water. Water spots are usually completely dry and will wipe away clean with a barely damp rag. Mildew, however, is often powdery and will smear slightly when wiped gently.

Other Common Household Areas for Mildew

  • Kitchens – Look for mildew in the kitchen around your sink, on countertops, and anywhere condensation from cooking forms.
  • Laundry Rooms – Mildew may grow in laundry rooms with poor ventilation. Look for it around the exhaust vent of your dryer.
  • Basements – If you have a damp, musty basement, look for powdery, white stains on walls, around windows, and anywhere moisture collects.

Most Common Places For Mold to Grow

Like mildew, mold will grow anywhere where the conditions are right. However, it is most common in basements, bathrooms, kitchens, laundry rooms, and anywhere with persistent water issues.

  • Basements – Mold is common in basements, especially if they are unfinished. Open sewer drains, ineffective waterproofing, weakened window seals, pipes and plumbing fixtures, and laundry facilities all can provide the necessary water for mold to thrive.
  • Bathrooms – As with mildew, mold is common in bathrooms due to the moisture, temperature, and materials involved. Slow leaks may also lead to mold under sinks and behind toilets.
  • Kitchen – Look for mold in the kitchen under and around sinks and anywhere condensation forms.
  • Laundry Rooms – Mold is common around dryer vents, in drain tubs or utility sinks, or anywhere items remain damp for an extended period of time.

How to Treat Mildew

Since it is very slow to grow and poses little risk of damage, you can treat mildew with a thorough cleaning. While mildew may still return, regular cleaning will usually keep it under control.

There are many cleaning products specifically targeted at mildew removal, but bleach is as effective and normally much cheaper. To disinfect surfaces contaminated with mildew, add three-quarters of a cup of household chlorine bleach to one gallon of room temperature water.

You can use a rag or a sponge to scrub surfaces or pour the bleach solution into a spray bottle. Allow the solution to sit for two minutes before wiping dry. Alternatively, allow it air dry. If you see mildew, we recommend scrubbing gently with a wrap first. Then continue to spray the surface once a week to ensure the mildew does not return.

How to Clean Mildew

  1. Mix three-quarter of a cup of bleach into a gallon of room temperature water.
  2. Use a rag or sponge to scrub surfaces contaminated with mildew.
  3. All the bleach to sit for 2 minutes.
  4. Wipe dry with a clean, dry rag or allow to air dry.
  5. Mix a new batch of bleach solution together each week and spray surfaces to prevent mildew from returning.

Other Ways to Preventing Mildew From Returning

In addition to regular cleaning, there are several steps you can take to prevent the return of mildew. These steps will also help prevent mold as well.

  • Improve ventilation in bathrooms, kitchens, and other areas where mildew appears.
  • Clean and dry areas with staining water immediately.
  • Use a dehumidifier in areas prone to excess moisture, humidity, or condensation.
  • Avoid leaving wet materials like clothing and towels piled up for an extended period of time.
  • Wash and dry kitchen and bathroom towels, washcloths, and rags regularly.

How to Treat Mold

Unlike mildew, mold isn’t so easy to remove. While you can clean mold with a bleach solution, it is likely to return if you don’t address the source of moisture first. Even if you fix the water source, mold can remain deep within walls and other materials for a long time. This may result in continuing health risks as well as the decomposition of those materials. If you have mold, it is best to ensure it is completely removed.

How to Remove Mold

While the mold removal process will vary from situation to situation, these basic steps apply in almost every case.

  1. Local the Water Source – Identify the source of the moisture that is allowing the mold to thrive.
  2. Repair the Water Issue – Next, you need to repair the issue. Otherwise, the mold is guaranteed to return.
  3. Dispose of Contaminated Materials – Mold will remain within materials even after fixing the water problem. This can cause continued problems, so you need to dispose of items contaminated by mold.
  4. Dry the Area – To ensure the area is completely dry, use fans, air movers, and dehumidifiers. Allow them to run for at least a full day after materials appear visibly dry. Two days is preferable. Check with a moisture meter when possible.
  5. Clean and Disinfect – Spray the area with a disinfectant solution to kill any remaining mold spores.
  6. Reconstruction – Finally, rebuild the area to your desired specifications.

Mold Removal From a Certified Company

If you have mold or are concerned you may have mold, it’s best to get a visual inspection from a certified mold removal company. They will look at the situation and make a professional recommendation. If you have a mold problem, they can begin mold remediation immediately. If necessary, they can even provide a mold test.

Restoration Local is the nation’s #1 network of restoration contractors. We have listings for local mold removal companies across the country, including the most popular franchises like Bio-One, PuroClean, and Restoration 1. For immediate service and a free estimate, call 1-888-443-3110 now to speak with our on-call mold removal contractor in your area.

Author: Jeff Rooks

Jeff Rooks writes restoration content that helps homeowners restore their lives after a disaster or accident. Most days, you can find him cycling through Tampa. He also enjoys exploring new and delicious food and beverages around the world.

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