Past Water Damage? Need a Mold Inspection?

May 18, 2020

We often get calls from clients with concerns about moisture problems that happened in the past. They are concerned that a past leak or other water-related problem in their property caused mold growth that is not readily visible. If you’ve had past water damage, should you get your property inspected for mold?

Unknown Water Damage

The only way to know if there are high levels of mold and possible moisture problems is by having an inspection completed.  When we perform an inspection, we first look for moisture using an infrared camera and moisture meter. With these two pieces of sensitive equipment, we can detect areas of current moisture in walls, ceilings, flooring, etc.  We spend a lot of time inspecting the building for dampness to find any leaks or other moisture-related issues that may have gone unnoticed. I’ve completed several inspections where a property owner scheduled a mold inspection as a proactive measure, with no specific concerns in mind. Many times during these inspections, I have found moisture problems that the property owner did not know about.

Past Water Damage

When a client schedules an appointment due to past moisture problems, they typically want to assess if the previous water damage caused mold growth. When no moisture problems are discovered, air samples are often collected to determine the airborne mold levels. A common industry practice is to collect a minimum of three air samples. Two samples are collected indoors and one outside. One indoor air sample is collected where moisture or visible mold is discovered or in the area of highest concern.  For the topic of this article the area of highest concern will likely be the area where the past moisture problems occurred.  The second indoor air sample is placed elsewhere indoors in an area unaffected by the past moisture problem as a control. The outdoor sample is also a control sample, used to gather a baseline level of mold in the outdoor air. 

Two Different Experiences 

I recently performed an inspection at a property where the owner was experiencing respiratory health effects from an unknown source. Her doctor suggested she have her home inspected for mold. She did not know of any current moisture problems but did know that the previous homeowner disclosed that the dishwasher leaked. During my assessment, no current moisture was detected and no visible mold was found. An air sample was collected in the kitchen area where the past moisture problem occurred. A second sample was collected in the master bedroom, and the third sample was collected outdoors. In this case, the indoor air samples demonstrated similar types of mold at similar quantities, indicating that there was not a mold problem at the time of the assessment. 

I found myself in a very similar situation at a different property. The owner experienced health effects but did not notice any moisture problems in his beautiful, recently rehabbed condo. Unfortunately for him, the air samples for mold showed very high levels of mold, including toxigenic mold types. The owner knew that there was a past toilet overflow and dishwasher leak so we recommended hiring a separate company to safely remove some building materials to get a better look, following best practices of course. There was mold everywhere! There was mold behind the dishwasher, behind the cabinets, underneath the wood floor, etc. It was a major job to cut away and professionally remediate the property. After the work, we were able to clear the job with a post-remediation verification assessment. Air sampling for mold has its limitations, but in this case, it really helped alert us to a hidden mold problem. More information can be found on the CDC’s website.


If you have any concerns that there may be mold in your home, the best course of action is to have a professional perform an assessment. I will say that typically when no current moisture or visible mold is discovered the air samples tend to be fine. However, there is always a chance that high levels of mold are present but not readily visible. When in doubt, check it out, or better yet hire us to inspect!