Mold - Where and How Does It Grow?

Aaron signed as he sat his soda can on the table.  True to form, he couldn't finish a drink before it hit his bladder.  Excusing himself from the room, he quietly went to the bathroom.  The door was locked.  "Must be one of their kids," he thought.  Maybe John and Sarah wouldn't mind if he used their master bath, since he had about 30 seconds before the filtered soda would leave his bladder, whether he was in an appropriate spot or not.

As he closed the door and lifted the lid, Aaron noticed the dark staining on the wall and on the baseboard behind the toilet.  "What in the world?" he muttered, and then he recognized that it was mold.  Growing along the wall, it was all the way from the vanity to the tub.  It gave him the chills to know that his best friend lived in such filth.  He quickly finished and gratefully closed the door behind him as he eagerly returned to the party, thinking of any excuse to leave as soon as possible.


Mold requires 3 ingredients to grow; mold spores, moisture and a food source.  Once all three components are in place, mold can begin to grow most any place.  All homes and businesses, regardless of how clean, have mold spores and food sources readily available.  All that is missing is the moisture for growth to start.

While mold can grow in nearly any location in your home, there are a few places where it is much more likely to start.  Regular inspection of these places will help to prevent or reduce mold growth.  Regular means daily if you are paranoid, or once a week to once a month if you are conscientious.

1. Under sink cabinets - Sink cabinets always have water lines.  It is possible for a small or large leak to begin most anytime in either the supply or drain lines.  The older the plumbing, the greater the chance of a leak forming.  They can occur from old gaskets, rusty pipes, or worn-out fixtures, etc.  Once a pin-hole leak starts, the water will erode the hole larger and larger until a drip every day becomes a steady stream.  Because we seldom inspect under the sink, mold can grow undetected for quite some time.
2. Behind and under your fridge - Water and ice lines to the fridge are fragile.  They are usually 1/4" lines of either plastic or copper tubing.  As the fridge is moved in and out for cleaning and inspection, it is easy for the tubing to be crimped or run-over by the wheels, causing a small hole to develop.  Movement and vibration also loosen the fittings, allowing water to leak out.  A slow, steady drip can become an adequate source of moisture for mold growth and remain unnoticed for weeks.
3. Around tubs or showers - In these locations, there is soap scum and bodily oils that collect in corners.  These are food for mold to grow.  If the shower is wiped down or cleaned regularly and the room is properly exhausted, you can minimize mold growth.  Also, over time, the joints and corners of tile and cultured marble surrounds, develop cracks.  These will allow water to seep into the framing under the shower and start mold growth under and between floors, as well as onto ceilings below.
4. Exterior windows and doors - Windows, especially in the colder climates, are frequent haunts for mold.  Dust and water condensing on the glass collect on the sills and provide a perfect environment. This is particularly true when heavy drapes and curtains are over the windows and seldom if ever opened allowing the moisture to build up and condense.
5. Around any other water fixture, i.e.; toilets, water heaters, boilers, swamp coolers, etc. - The older the home, the more likely a leak can begin.  Water heaters have warranties that range from 5-12 years.  They are usually pretty good at not lasting much longer than the warranty.

Here are a few of the less likely places I have seen mold grow.

1. Attics - If you have a leak in the roof, the water will provide the environment for mold to grow.
2. Crawl spaces - Some locations have extremely high ground water.  This water can condense on the framing members and start mold growth.  Venting crawl spaces as per code, as well as installing moisture barriers on the dirt, will greatly reduce the chance of this happening.
3. Between the layers of vinyl flooring - Often the wax ring that seals the toilet to the drain will develop a hole allowing water to seep out along the sub-floor, under the vinyl.  When this water penetrates the layers of paper in the vinyl, mold can grow.  This generally creates a grey to purple stain in the flooring.  It looks much like someone spilled grape juice and it stained.  No matter how hard you scrub or what cleaner you use, the stains will not come off.  The only solution is the vinyl has to be replaced.
4. Sub-flooring under wood or laminate flooring - In the event of a water leak or flood in a room with laminate flooring, the foam or plastic barrier under the laminate will trap moisture next to the sub-flooring material, allowing mold to grow.  Often it takes months to years for this water to dissipate.
5. Exterior walls behind furniture - Mold in these areas usually grow from one of two sources.  First, water intrusions from the outside such as sprinklers or rain water.  Second, high humidity in a room that condenses on the cooler locations behind the furniture near the floor.  Either of these reasons need to be corrected before effective remediation can occur.

Regardless of where or how mold begins to grow, the guiding principles of remediation are:

• Correct the source of water.  If the source is not stopped, mold will begin to grow again within a few weeks of the repairs.
• Remove and dispose of all damaged material.
• Wipe and HEPA vacuum the area until clean.