How do home inspectors measure for moisture – and how SHOULD they measure for moisture?

Moisture Meter

The most prevalent but least accurate way home inspectors measure moisture is through a moisture meter.  Essentially, this meter measures SURFACE moisture.  This is the quick and easy method used by most home inspectors to measure moisture inside a home.  Please note: If utilized to measure moisture on the surface of a foundation wall, the moisture meter must be used in conjunction with a complicated mathematical formula that is usually beyond the expertise of most home inspectors.

Moisture Meter with Short Probe

The second way to measure moisture is with the same moisture meter, but using a ½ or ¾ inch probe to check inside walls or floors. While this probe can identify moisture issues in the substrate material, the probes only go so deep.  As a result, moisture issues can be present deep inside the wall cavity without this probe showing elevated moisture levels.

Moisture Meter with Deep Wall Probe

The third way to measure moisture is with a deep wall probe.

Most home inspectors never use a deep wall probe, even if they identify potential moisture issues. This probe can be used to measure moisture deep inside interior and exterior walls and provides a more accurate assessment of water intrusion than the surface moisture meter.  A deep wall probe can also be used to measure moisture inside stucco and stucco-like material called EIFS that has been known to result in moisture issues and rotting.

If water penetrates these exterior surfaces, your home could be rotting from the inside out – without your even knowing it – until a major, expensive repair is required.  After conducting a thorough inspection and checking for potential moisture intrusion through the foundation walls, an experienced, highly-trained inspector may also use the deep wall probe to check the wall plate in areas of potential water intrusion.

Questions to Ask Your Home Inspector

Before hiring a home inspector, ask if he or she will be using a moisture meter, a moisture meter with probes, or a deep wall probe to measure moisture within the home.  Also ask if your inspector will measure moisture inside the wall plate – where and why.  Asking these questions will tell you a lot about your home inspector, his or her level of training, and overall quality of inspections.

Knowledge is power!