HOME MOLD AND MILDEW

The term mildew usually refers to certain types of mold which grow flat like on bathroom caulk and shower curtains or, in some circles of people, mold that grows on fabric. Other types of mildew are plant pathogens or parasites including powdery mildew and downy mildew. The term mildew comes from Old English and was formerly used to describe a substance secreted by aphids that was thought to be a kind of dew from the air. Molds, including those referred to as mildew, play an important role in our ecosystem, by breaking down or decomposing dead plants and animals in our environment. Problems arise for homeowners when these organisms take hold inside a home and begin feeding on building materials, affecting the look, smell, and even the structural integrity of the home.

To grow and reproduce molds need a food source and a moisture source. One favorite food source for mold in a home is the cellulose in the paper backing on drywall, wallpaper, and insulation. Glues used to bond carpet to backing and laminated surfaces to wood cabinets are another common mold food source. When a moisture source such as a plumbing or roof leak exists, mold will grow and spread, consuming organic materials in the home. Mold and moisture create a smell that we refer to as “musty”. Mold odors are unpleasant and indicate an airborne mold problem which can have serious health effects for inhabitants of the home. Air sampling for mold analysis can be performed to test for the presence of a hidden mold source.

10 Home Mold and Mildew Problem Areas

Below are 10 areas of the home where mold and mildew are commonly found along with advice on preventing mold growth in these areas.

Home Mold and Mildew Problem Area #1: Exterior Walls

When beginning an inspection, most home inspectors and mold inspectors observe the grade of the land surrounding the home. Functional grading should provide proper drainage away from the foundation perimeter. Water pooling at the foundation will eventually penetrate concrete (which is porous) and can cause water damage to other areas of the home. Many times shrubbery or hedges planted next to a home will develop a root structure which, over time, changes the original grade and forces water toward the foundation. Gutter downspouts that leak or are missing extensions or splashblocks may also direct water toward the foundation of the home.

Most people know that wet building materials like drywall, trim, framing, carpets, wood floors and subfloors, etc. are more likely to grow mold if they are not dried quickly. What most people don’t realize is that concrete blocks are porous and mold can actually grow in the block walls. There is no way to remove the mold from the block, so the block must be sealed from the inside with a mold-resistant encapsulant.

Beyond the base of the exterior walls, the entire surface of the exterior walls should be checked annually for cracks. Settlement and expansion cracks should be sealed to prevent water intrusion.

Home Mold and Mildew Problem Area #2: Crawlspace

Poorly constructed crawlspaces and those with poor grading beneath the building promote growth of home mold and mildew. Bare earth floors hold large amounts of moisture. Depending on the location of the home, there are many regional solutions. The crawlspace can be cooled or dehumidified along with the rest of the home. This may be an expensive option with rising energy costs. A less costly solution is to cover the bare earth in the crawlspace with 6-mil poly sheeting. This should only be done if the ground in the crawlspace is properly graded to allow water to drain away from the building. Otherwise, as in the picture on the right, water will collect and remain stagnant leading to increased mold growth as well as bacterial growth and mosquito infestations.

Home Mold and Mildew Problem Area #3: Attic

Moisture in attics can come from several sources. Leaky ductwork can introduce cool air into the warm environment of the attic and create condensation providing the moisture source for mold spores to begin a new colony. Infrared thermal imaging cameras can be used to detect leaks in the ductwork and moisture in the insulation in the attic. All leaks in the ductwork should be sealed with the proper kind of tape (not duct tape as it is not long lasting).

If an air handler is located in the attic, it will naturally produce condensation in certain areas. Small areas of circular growth found on the exterior of the unit may be an indication of a larger mold problem inside. Stagnant water in the condensation pan can provide another source of moisture the mold spores need to grow. The pan should be checked prior to each cooling season and cleaned with a 1% bleach solution. This will also help to keep the drain line clean. Pour a bleach solution down the drain line more frequently if the line has backed up in the past.

Bathroom and clothes dryer exhaust vents terminating into attics can create favorable conditions for mold growth. Many times mold can be seen growing in small circular patterns on the top of ductwork in the area where this moist air is introduced to the attic. Bathroom fans and dryer lines should be vented through the roof to the outdoors. Alternatively, kits are available to route both to the outdoor air through the building’s soffit vents.

Home Mold and Mildew Problem Area #4: Roof

Roof leaks can cause large areas of mold damage. Cracked or damaged chimneys are a common cause of leaks. Any other roof penetrations, like skylights, and plumbing or laundry vents are also common culprits. Some people say that there are two kinds of skylights: One’s that leaks and one’s that are going to leak. Areas where different materials meet, such as shingles and block wall or metal and brick, expand and contract at varying rates and may eventually crack at the point where the materials meet and cause water intrusion.

Roofs should be inspected at least twice annually. Roofing materials will weather in the intense Florida sunlight and heat, becoming brittle (alligatoring), split, and eventually leak. Metal roofing components can rust and corrode, and asphalt-based materials uses to seal around pipes, vents, and other roof penetrations may deteriorate and leak over time. Products are available to coat problem areas with a layer of waterproof protection. The ceilings of the home can be scanned with an infrared thermal imaging camera to detect leaks from the interior.

Home Mold and Mildew Problem Area #5: Windows

Water intrusion may occur around windows that are improperly flashed or caulked. Look for signs of moisture in the drywall surrounding windows. Have a thermal imaging inspection to help determine the exact source of water intrusion and the extent of moisture migration which is usually further than the naked eye can see.

Windows with large amounts of surface condensation create favorable conditions for mold to grow on the window frame and glass, on adjacent drywall, and on nearby framing and insulation. Condensation can be minimized with good ventilation and airflow.

Home Mold and Mildew Problem Area #6: Air Handler and Ductwork

When mold grows anywhere in a building, it will eventually release spores into the air which can travel through the A/C system to all areas supplied by that unit. The condensation in the air handler provide a moisture source for mold to grow in and around the air handler and the ductwork.

The coils of the air handler should be cleaned periodically. The drain pain where the condensation from the coils drips should slope properly toward drain lines so water does not remain stagnant causing mold and bacterial growth. Filters in the HVAC system should be change regularly to help prevent spores from spreading. Insulation inside the air handler with any signs of mold growth can be tested with a tape lift surface sample. If mold has grown on the insualtation it should be removed or replaced.

UV lighting may kill some mold, but not all. Below are pictures of two air handlers with heavy mold growth in close poximity to UV lighting:

Home Mold and Mildew Problem Area #7: Bathrooms

A major cause of water and mold damage in bathroom is poor grouting or caulking in the shower or bathtub area. Even small cracks in the grout can allow water to penetrate into the dark cavitiies behind the shower walls. Signs of damage may be minimal, as in the pictures below, but the toxic black mold Stachybotrys grows well in these areas with a constant source of moisture. Check bathtub and especially shower tile grouting for cracks regularly and seal with grout or caulk immediately when detected. Wall cavity air sampling is recommended in cases where water intrusion appears to have occurred.

Plumbing leaks can cause large areas of water and mold damage, much of which may be hidden from view. It is important to determine how far the water has spread and to have these areas dried immediately or mold will likely grow. Surface mold can grow in bathrooms with poor ventilation. Florida homes should have bathroom fans installed to transport moist bathroom air outside of the building. This is not mandatory if the bathroom has an exterior window. If moisture is not exhausted from the bathroom, mold may begin to grow on windows and walls. Another favorite place for mold to grow in the moist bathroom environment is on the back of wallpaper using the glue as a food source.

Home Mold and Mildew Problem Area #8: Washers and Water Heaters

Washing machines and water heaters, especially those higher than the first floor, should have a drain pain with a one inch lip that drains to the exterior of the building.

Home Mold and Mildew Problem Area #9: Wall Coverings

Impereable wall coverings made from vinyl or other materials can trip moisture rich air, especially on exterior walls where the warm exterior meets the cool interior of the building. The moisture enables mold to grow using the wallpaper glue as a food source. Mold will commonly grow in behind the wallpaper in bathrooms due to moisture in the air. Use only wallpapers with permeable paper backings that wont trap moisture.

Home Mold and Mildew Problem Area #10: Kitchen

Mold can be a serious problem in the kitchen. Water damage often goes undetected behind cabinets and appliances. Water can wick up cabinets quickly and mold growth can begin in days, especially in cabinets made of pressed wood or particle board. Water will also wick up the walls behind the cabinets in a perfect environment for the growth of toxic black mold. The interiors of kitchen cabinets should be cleared and inspected periodically (more frequently with overstuffed cabinets) for signs of plumbing leaks and water damage. Infrared thermal imaging inspections are available to get a better view of water damaged areas.

Be sure to check the caulking around the sink and the grout or caulking where the countertop meets the backsplash or wall for areas where water might seep into or behind cabinets.