Mold Top 10: Ten Places to Find Mold in your Home

To ring in the new year, TMP's January blog lists out the top ten most common areas to find mold in the home. This is a key part of our inspection process and understanding building sciences to get an accurate sense of your homes fungal ecology.



In today’s blog I’m going to go over the different locations that mold could be growing in your home.  Mold can grow almost anywhere in the home as long as there is a food source and moisture.  Moisture can be obtained through some type of water event (i.e., a leak) or just through the humidity in the air.   Another misconception is that newer homes are less likely to have mold, however through my work and the work of others I have seen newer homes inundated with mold than more commonly than older homes (homes built before 1970).  This is because newer building materials are better food sources for mold (1).  

As seen from Figure one from Becher et al. mold grows better in some parts of the home than others (2). The best environments have three elements moisture, food source, and darkness.  In this article I am going to detail the ten most common places that can grow in your home.


1. Basement

Basements are notorious for mold growth.  There area lot of underlying factors which can cause moisture to build-up in abasement.  Foundation issues and drainage from poor sloping in the yard can lead to a lot of water ending up in abasement.  HVACs and water heaters could leak or produce condensation, which will also lead to water accumulation.  Using dehumidifiers could be helpful in preventing problems.  As I’ve stated in previous blog posts; keeping your humidity below 50% is very important in keeping mold growth down.  

2. Attic

The Attic is the second common place that we find mold. The most common problem with attics is leaky roofs, which then leads to growth on wood structures in the attic. Another common problem is that bathroom fans dump a lot of moisture into the attic, which in turn increases the humidity of the attic space.

3. Bathroom

Bathrooms are extremely problematic, but not in the ways that most people think.  People focus on mold and bacteria growing in showers/bathtubs; however, they miss the mold growing behind drywall, in vents ,and under the sink.  Because of high humidity in bathrooms, dust in the ducts next to bathrooms could be problematic for mold growth.  Second, because of plumbing issues we frequently find mold growing under sinks.  Sometimes mold is growing behind the walls or under the floor boards.  We sometimes have to perform intracavity searches to look inside tight spaces which are visible normally.  

4. Crawlspace

Crawlspaces are problematic because they are often not environmentally controlled.  Build-up of moisture or humidity can lead to mold growth.  Installation of devices to mitigate humidity and fixing sources of water can help prevent mold growth.  In addition, adding in barriers between the crawlspace and living areas can help prevent mold spores and toxins from entering areas where they could cause illnesses to people and pets.  

5. HVAC and Ducts

HVACS and ductwork can be reservoirs of both mold and mycotoxins. Dust buildup can provide food for ongoing mold growth, or it can just hold onto poisonous mycotoxins. Additionally, the warmth, condensation, and humidity that could be moving through the vents make this an ideal place for mold to thrive.  We typically recommend clients to get their ducts cleaned before we perform treatment to their homes.  This will help to remove any potential future problems and opens up the surfaces in the HVAC and ducts for our enzymatic cleaners to degrade the mycotoxins.  

6. Kitchen

The kitchen has multiple areas where water can be an issue. The most common are the sink and the dishwasher. Make sure to clean up any water issues as quickly as possible. Any mold issues in the kitchen are magnified since food is prepared and stored in the kitchen.  

7. Walls

Many newer homes use materials that are great food sources for mold.  Water intrusions behind walls will lead to mold growth that can last after the water incident has ended.  These types of incidents include leaky roofs, leaky windows, flooding from rain, pipe issues, toilet issues, etc.  Once mold has started to grow behind a wall sometimes the only way to know it is there is through mycotoxin testing.  That is why we frequently test for environmental mycotoxins in homes.  The spores from the growing mold may be trapped behind structures, but the mycotoxins (which are much smaller) will be moving freely through the living area.  This will lead to health affects in the inhabitants, but a problem that may be difficult to see and smell.  Other methods that we utilize to find the mold are infra-red cameras, intracavity sampling, and borescopes.  

8. Carpets

One of the frequent questions that I receive is “what to do with carpet when you have mold.” There are several reasons why I recommend to get rid of carpets.  One is that they are frequent reservoirs of mold and mycotoxins.  Carpets are made from items that mold can use as food sources. Mold can thrive inside and under carpets and rugs.  Keeping them dry and frequent cleanings can help in preventing issues.  However, if we are dealing with a patient that is dealing with CIRS or immune issues, then I definitely recommend removing the carpets and rugs.  

9. Windows

Windows are great items to have in your home.  You can open them up to let in fresh air and they bring in natural light from the outside.  However, rain can penetrate the structure either through parts of the window or through the framing around the window.  The heat from the sun can be trapped by the window, which then can assist with mold growth.  Checking around windows is a must for any mold inspector.  

10. Laundry Room

The last area we will spotlight is the laundry room. Obviously the most common problem area is the washing machine.  Washing machines are the perfect mixture of dark space, moisture, and heat.  In addition, water leakage could cause problems on walls around the laundry room.  Another possible problem is wet and dirty clothes which could lead to mold growth.

If you have additional questions, I would recommend looking at some of my earlier blogs, if you haven’t already.  Also, feel free to fill out a contact from if you have any questions that you can’t find an answer to your question on our website.  Another source of info that we have is our monthly webinar series. Please feel free to look at our past webinar and sign up for our future ones. We hope we can help you through your mold issues.  

Resource List


1. B. Andersen, J. C. Frisvad, I. Sondergaard, I. S. Rasmussen, L. S. Larsen, Associations between fungal species and water-damaged building materials. Appl Environ Microbiol 77, 4180-4188 (2011).

2. R. Becher, A. H. Hoie, J. V. Bakke,S. B. Holos, J. Ovrevik, Dampness and Moisture Problems in Norwegian Homes. Int J Environ Res Public Health 14 (2017).

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