Common Causes of Basement Mold

Updated by Lisa A on January 25, 2019 in

Mold Remediation, Mold Testing, Mold Inspections

Mold is ubiquitous in both indoor and outdoor environments. When temperature and moisture conditions are favorable, mold can grow rapidly, causing much destruction to property and endangering human health. Because basements tend to be damp and dark, an environment conducive to mold growth, this is one of the areas in your home where mold is most likely to be present. Below are some of the most common causes of mold growth in a basement setting. 

Basement Mold


Missing or clogged gutters

Rain gutters are troughs that run the periphery of your roof designed to collect and funnel rainwater. Without gutters, rain simply runs off the edge of the roof and lands near the  foundation, creating the potential for seepage into the basement. Rainwater falling in sheets to the ground around your home can be a powerfully destructive force. Unless your roof has a significant overhang or is located on a fairly steep slope, you'll want gutters and downspouts to divert water away from your home and its foundation. 

When gutters are in place but are clogged, the consequences are similar. Rainwater, rather than being appropriately channeled toward the downspouts, ends up spilling over the sides of the gutters and pooling around the foundation. Once the ground is saturated, the likelihood increases that water will penetrate any existing cracks. Once there, the expansion and contraction that accompanies the freeze-thaw cycle works to enlarge the cracks and cause further deterioration, eventually allowing water intrusion into the basement, and mold growth.


Detached downspouts

Downspouts convey rainwater collected by gutters downward, often discharging it into a sewer pipe that leads to the municipal sewer system. Some downspouts are redirected, via an elbow and an extension to a desired permeable area away from the house, such as into the lawn, a garden, etc, where the rainwater can infiltrate the soil.

A downspout that has become detached due to high winds, ice formation, or simple deterioration, will not serve its purpose of directing water away from the house and instead will allow it to hammer away at the ground encircling the foundation. Mold specialists seeking to identify the source of water intrusion will often have downspouts at the beginning of their checklist. Visible mold in basement corners is a hallmark of detached downspouts. 


Poor land grading

Grading refers to the slope of the land around your home. Ideally, your home will sit at a higher point, with the land sloping downward away from it. This type of grading would cause any water to flow away from your home, toward the lower elevation, preventing pooling around the foundation. An ideal slope is usually considered 1 or 2 percent, depending on the smoothness of the terrain. 

Though new construction must meet lot grading guidelines, property over time can undergo grade shifting as the house and surrounding land settle, and additionally after removal of trees or shrubs, or sometimes in cases of animal activity.

Of course, any of the above conditions that results in a water intrusion event and mold infestation would need to be addressed and corrected before remediation should occur. A qualified mold remediation specialist will have the necessary experience and tools to identify the issue, and help resolve it.

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 Thanks to our mold remediation specialist Zach C for lending his expertise to this article.


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