What Causes Mold to Grow?

Answer: Water and Organic Nutrients

We are surrounded by low amounts of certain species of mold on a daily basis everywhere we go. These fungal spores are naturally occurring outside and some end up inside because of that. The question we are addressing here is not exactly what causes mold but how does mold thrive in an indoor environment. As you see above the answer to that is water and organic nutrients. Water can come into the equation via rain, pipes, oil, or condensation. Here is a general list of organic nutrients mold loves in an interior environment:

  • Cellulose Products (Paper / Drywall)
  • Wood
  • Glue
  • Insulation
  • Fabrics
  • Carpet
  • Dirt/Grease/Oil

If you can visualize tiny mold spores in the air looking for a combination of water and any of the above products to land on, they will colonize as long as that moisture is there and they have not used up all the available organic materials.

Temperature and Humidity

Mold needs a relatively warm environment to grow, which is one reason it is found in so many homes. Homes that are kept cooler may experience less mold growth. When temperatures are higher, humidity has a greater chance of rising as well and with that comes moisture. Optimal conditions for mold growth are above 70 degrees Fahrenheit and over 60% humidity.

Leaky Pipes

Pipes with many seams or those that are older can be prone to leaks. While a few drops of water may not seem like a lot but over time, it can cause thousands of dollars in damage and provide the perfect moist conditions for mold.


Inadequate ventilation or a lot of people living in a small space can lead to condensation. Bathrooms are common places for condensation to occur due to bathing. The more showers you take, the more condensation. A vent fan can help prevent issues as well as making sure water is mopped up and not allowed just to sit on surfaces.

Dark Spaces

Mold loves a darker environment, so a brighter and better-lit home is less likely to have it. Mold cannot grow under ultraviolet life. The love of dark spaces also means that mold is growing in places where you won’t notice it until there are more severe allergy symptoms. One treatment for mold is to expose it to ultraviolet light for a brief period.

The Mold Growth Cycle

One of the most important things to remember is that mold requires water to grow and thrive. Usually, a leak or similar occurs, and mold spores find their way to the moisture and begin to grow if temperatures are right. When molds have the right conditions, they can grow hyphae that release more spores into a space. The cycle will continue until something is done to treat the moisture problem and remove a load of mold and spores within the home.

Getting Help

Mold can be very serious because of the effects it can have on your health. There are 16 known types of mold that occur in homes. Black mold is one of the most likely to cause severe health issues, but there are plenty of others that can make you have severe allergies and lead to infections.

A mold test will allow you to determine what type of mold you are dealing with and at what level it is present in your home. A self-test kit is used by those that wish to collect their samples and mail them to a lab. Those that use self-test kits should be aware that without experience the results could vary. A professional mold service can take tests more quickly and easily and offer valuable advice on removal, costs, and help you plan for repairs to your home.