Mold (or mildew) is a fungus that fills an essential role in nature of returning nutrients to the earth by breaking down organic material. Mold spores of all kinds are absolutely everywhere in the world, even within the driest of homes. Mold becomes a concern when those spores are able to propagate and grow substantially within the home. The overall concern is two fold:

Sickness can result from the increased concentrations of mold spores when active growth in the home reduces air quality. The susceptibility of people living in the home varies based on the quantity of mold and each individual’s reaction. People with asthma are particularly vulnerable to symptoms.

Deterioration of building components results as mold feeds of organic materials. Rotting wood is essentially the process of mold breaking down the cellulose of the wood.


Mold spores need three conditions in the correct quantity to begin growing and propagating:

  1. Moisture
  2. Food source
  3. Temperature
Mold growth within a home is almost always the result of preexisting moisture. You’ve probably noticed that, given enough time, it’s almost impossible to keep a piece of bread or cheese from eventually becoming moldy. Just like bread and cheese, wood, paper, and many other building components are a potential food source for mold to attack. Add a little moisture or humidity to the mix and it’s not at all uncommon for an inspector to find mold or conditions that are conducive to mold growth during the inspection.



By far the most common place that substantial mold growth is found during the inspection is in attics. With few exceptions, attic spaces need to “breath.” If the attic does not have sufficient ventilation, humidity and condensation that accumulates there has no way to dry out. This creates a perfect environment for mold to grow. Of course, mold can grow just about anywhere in a home but here as some locations where I’ve find it more frequently:

  • Converted Basements. Improper or missing water barriers and poor drainage systems are the usual culprits here. Mold that’s behind the walls can easily go unnoticed until the walls are removed.
  • Floor Structure. Mold that occurs beneath the floor or in crawlspaces usually manifests in the form of “dry rot”
  • Shower Enclosures. Moisture that makes its way past a shower enclosure can easily translate to mold behind the walls. I encountered this frequently during demolitions as a remodeler.
  • Behind Furniture. Sometimes just the number of residents and poor ventilation in a home makes wall surfaces vulnerable. Furniture against the walls can create a particularly humid undisturbed environment.


Even when mold growth cannot be seen directly, there are often clues indicating it’s presence or potential to grow. Musty odors, discolored sheathing, and “dry rot” are all indicative of excess moisture and resulting mold growth. It’s important to know that a standard home inspection does not do any specialized testing for mold. A mold remediation contractor or air quality specialist may be able to test for the presence of mold that is otherwise not visible.


Small amounts of mold or mildew in isolated areas can often be removed by the homeowner. The CDC recommends cleaning mold growth from hard surfaces “with commercial products, soap and water, or a bleach solution of no more than 1 cup of bleach in 1 gallon of water.”

If indications of significant mold growth are present, further analysis by a licensed mold remediation contractor may be necessary (see “Service Providers” below). A mold remediation contractor can determine the extent of any health concerns and advise what steps should be followed to correct and prevent mold growth.


Environix (mold inspection, remediation)
(425) 563-6480

(425) 649-0600

Please note that the information and resources provided here are intended only as a courtesy by Wil Harnecker and HAUS Inspection Services, LLC.. This information is not intended for use in making real-estate or other financial or health related decisions. Further research and due diligence is always recommended during all steps of the home buying and selling processes.