Extreme case of mold on a ceiling

Culture on the left treated with antimicrobial agent, preventing mold growth; right is untreated and mold has overwhelmed the culture.
At the Coverings show, held in Orlando, FL on March 23 - 26, 2004, the National Tile Contractors Association (NTCA) conducted a mold panel seminar entitled Mold In The Tile Industry. This panel, moderated by Bart Bettiga from the NTCA, included Mohammad Ali from Georgia Pacific Corp., Barry Wilson from Microban® International Limited, Art Mintie from LATICRETE International and Mitch Hawkins from LATICRETE International. This article is a summary of the presentation.

Mold is a fact of life. Mold is everywhere - outside, inside, on our clothes, and on our bodies. There is little we can do to eliminate mold in the environment, but then, why would we want to?

Mold and other fungi play a vital role in the natural process. If it weren't for mold, the world would be full of dead organic materials. Leaves, wood and other organic materials will continue to pile up in the environment. Mold plays the role of decaying the organic materials and allowing the decayed matter to re-enter the environment and provide a food source for future growth of vegetation. Mold is also used for human good in other ways. One species of the mold penicillium (Penicillium Notatum) is used to manufacture penicillin. Molds and fungus are also used in the manufacturing of wine, bread, cheeses and more.

Unfortunately, most people do not see the good that mold performs. Many of us have heard or seen the stories about toxic mold and its effects on people, homes and the work environment. We see mold, often in showers, and go to great lengths to get rid of it once and for all. It is important to understand that this is a war that we will never win outright, but that we can control.

What exactly is mold? In a nutshell, mold is a living organism that grows on virtually any organic substance. Mold is a member of the family known as fungi, which includes mushrooms, yeast and mildew. Fungi lack chlorophyll to create food by themselves, so they rely on taking nourishment from organic food sources. There are roughly 100,000 types of mold known, of which some are toxic. Some molds that are considered toxic are Stachybotrys, Cladosporium, Aspergillus, and Penicillium. Toxic molds produce mycotoxins or aflatoxins that, when in contact with humans, may create health problems.

Let's look at what causes mold to grow in an interior environment. Mold requires 4 factors in order to grow and flourish; a food source, oxygen , warm temperatures, and moisture. If you can control any one of these factors, you can control mold. Let's look at each factor individually;

Food source - Mold thrives on organic materials. Paper, wood, dust, organic adhesives and many other organic based materials are viewed as mold food. If you are thinking that your house is made of wood and wood products, you are not the only one. In the right conditions the wood used to construct your house can be affected by mold growth. It would be next to impossible to remove all organic materials from the house so this is not an option.

Mold on gypsum board
Oxygen- Mold is a living organism and must have oxygen to survive. Eliminating oxygen in the house is out of the question - breathing is a good thing!

Warm temperatures - Mold likes temperatures in which people like to live. Molds do very well at temperatures between 65°F (18°C) and 90°F (32° C) as do humans. Since we do not like living at temperatures that can help control mold growth, than this is not an option.

Moisture - Mold needs moisture to grow. This can be any type of moisture including direct water contact, high humidity or water saturated organic material. Mold can get a foothold if there is no visible moisture but the Relative Humidity (RH) is 55 percent or higher. Moisture would be the easiest of the factors that we can control.

Finding out where moisture comes from and then fixing the problem are critical to helping control mold. There are a variety of humidity-causing conditions that can facilitate mold growth; inadequate construction detailing, lack of proper drainage, faulty plumbing, poor landscaping, dirty HVAC systems, and poor venting are among these.

Mold can grow anywhere that there is a food source and moisture (knowing that there will be oxygen and suitable temperatures in a home environment). These areas include behind wallpaper, under bathtubs or showers, in wall cavities, underneath flooring, in HVAC systems, or any other dark, damp area that contains a food source. Mold does not really have a use for materials that are not a food source such as plastic, vinyl, concrete or Portland cement products or ceramic tile. This is good news because there are materials out there that are going to help in the fight against mold.

But, doesn't mold grow on grout in bathrooms? Isn't grout made from Portland cement? Yes, many grouts are made from Portland cement and some are epoxy based, and, yes these materials are not considered a food source for mold. Then why do we see mold growing on these surfaces? The answer is that the bathroom is a great environment for mold - it has a ready supply of moisture and it has food sources that are often taken for granted. Soap scum, shampoo, dead skin, and even hair can be considered food sources and the fact that these can be on the grout would make it appear that the mold is growing on the grout. Portland cement products have capillaries, or small holes, into the body of the product and mold can appear to grow into these capillaries making it difficult to clean. It may also mean that there is mold growth underneath the tile or substrate and the mold is moving to the surface of the grout through the capillaries or cracks in the grout.

What Can You Do To Help Control Mold

As stated earlier, the easiest way to control mold is to control moisture.

A shower wall infested with mold
So the following are easy steps to help control moisture:

• Watch for condensation and wet spots - if you see wet areas, fix the cause of the moisture and dry the affected spot within 48 hours.

• Fix leaky plumbing and any leaks in the building envelope.

• Prevent moisture condensation by increasing surface temperature, properly insulating exterior walls and increasing ventilation.

• Replace HVAC filters regularly - HVAC systems are a great way for mold to move around a structure. HVAC duct work is not a food source but they almost always contain dust, or other food source, and moisture.

• Keep HVAC drip pans clean and flowing properly.

• Maintain an indoor RH of 55 percent or less by using a dehumidifier - humidity gauges are inexpensive and easily found at most hardware stores or home centers.

• Do not let foundations stay wet - concrete is hygroscopic (a very hard sponge) and moisture and moisture vapor passes through concrete readily. Make sure that the ground around the house is properly pitched away from the structure and, if necessary, install foundation drainage to keep moisture from coming in contact with the concrete. Moisture vapor can raise the humidity in the structure quickly.

• Keep an air space of at least 1 foot between furniture and an exterior wall to allow for air flow and give you the ability to see any damp areas.

• Make sure that the attic space is properly vented. Moisture vapor travels up and can collect in the attic space.

• Educate yourself and others about mold and mold related issues.

Controlling Moisture In The Bathroom

Here are some simple steps to take to control mold in the bathroom environment:

• After every shower or bath, dry the tub and tub surround with a towel. This will remove most of the excess moisture from the shower area and prevent it from aiding in mold growth. Don't leave the wet towel laying around for several days because it can also be mold food.

• Leave the bathroom vent fan on while showering and for 30 minutes, or so, after showering. This takes a lot of the moisture out of the air and deposits it somewhere else (hopefully outside). Make sure that the fan vents to the outside of the structure and not into the attic or another room in the house.

• Do not install carpet in a bathroom. Instead, install ceramic tile or stone.

• Establish and maintain a suitable cleaning regimen. Remember that soap scum, shampoos and other organic materials can be on the surface and unseen by us. Cleaning the surfaces will help to limit the amount of organic substances that can feed mold. Use a neutral pH soap and rinse well with clean water, then allow area to dry.

• Avoid using organic setting materials in a wet environment. These include organic tile adhesives (mastic) or wallpaper installed with an organic adhesive.

Tile Solutions for Mold

Several manufacturers in the allied products industry recognized the fact that mold was becoming a big issue in the building industry and looked for ways to help inhibit the growth of mold in tile installations.

Keep in mind, the use of anti-microbial products does not eliminate the need to maintain a suitable cleaning regimen. Anti-microbials will not inhibit the growth of mold located on the surface of the tile or grout if a food source is present there.

Information for this article was provided by Barry Wilson, Vice President of Business Development for Microban International Limited, and Mitch Hawkins, Technical Services Training Supervisor for LATICRETE International.