If you suspect you have a mold problem in your crawl space, here’s what to look for.
As a helpful tip: In most homes where we find mold in the crawlspace, we found it after being called out by a homeowner whose family had slight but persistent health problems — light coughing, red eyes, can’t sleep soundly, etc. Meaning, they first felt the symptoms, then asked us to find the mold.
These are some of the most common signs that can indicate mold growth in a crawlspace:
10 Signs of Mold Growth in a Crawl Space
- Musty Smell: A musty or earthy smell is often the first indication of mold growth. Mold releases microbial volatile organic compounds (MVOCs) as it grows, which are responsible for the unpleasant odor.
- Visible Mold: If you see mold on the wooden beams, insulation, or on the crawlspace walls, it’s a clear sign of mold infestation. Mold can appear as black, white, green, or brown patches or a fuzzy growth.
- High Humidity: High humidity levels in the crawlspace create a conducive environment for mold to thrive. If the air feels moist or you notice condensation on pipes or surfaces, it could be contributing to mold growth.
- Water Intrusion, Flood, Storms, Leaks: Any signs of water pooling, leaks, or damp ground in the crawlspace can indicate a moisture problem, which is a precursor to mold. Mold needs moisture to grow, so any source of water is a potential risk.
- Health Symptoms: If occupants of the house experience unexplained allergic reactions such as sneezing, coughing, throat irritation, or itchy eyes, especially when symptoms improve away from home, this could be a response to mold spores in the air.
- Wood Rot: Fungi, including mold, can cause wood to decay. If you notice that wooden structures in the crawlspace are deteriorating, it could be a sign of mold or related fungi.
- Pest and Bug Infestations: Pests such as termites and woodlice are attracted to damp and moldy environments. Their presence could indicate an underlying mold issue.
- Higher Energy Bills: If your HVAC system is working harder to maintain the right temperature, it could be due to increased humidity or damp insulation caused by mold and moisture in the crawlspace.
- Discoloration: Unusual staining or discoloration on materials such as insulation, vapor barriers, or storage items can be a sign of mold.
- Warped Flooring Above: Excessive moisture and mold in the crawlspace can affect the flooring above it, causing it to warp, buckle, or feel spongy underfoot.
What and Where Your ‘Crawlspace’ Is
A crawlspace is a type of foundation used in construction that provides a small gap between the ground and the first floor of a home or structure.
Your crawlspace is usually 2-3 feet high, allowing just enough room for someone to crawl inside, hence the name.
It often houses some plumbing, electrical, and HVAC systems, and allows (pretty limited) access for maintenance, repairs, and installations.
Crawlspaces can also help protect a house from flooding because they lift the house itself above ground level, but if not properly maintained and ventilated, they’re prone to moisture and humidity problems, which can lead to mold growth, structural issues, and poor indoor air quality—inside the part of your home where you do live.
