Hidden Moisture: What Meters and Thermal Cameras Can Tell You

Separate air readings from material readings

A humidity instrument describes the air at its location. A material moisture meter investigates a building material. EPA treats these as distinct tools. On your report, look for separate labels rather than assuming that every percentage describes the wall or floor.

Ask the technician to point to the physical location for each result. Was the reading taken in the room, at the wall surface, or in an accessible material layer? Write down the answer in ordinary words so the information remains useful when the next contractor arrives.

Find out what the number means

Manufacturers use different modes and scales. Protimeter, for example, distinguishes wood moisture equivalent readings from its non-invasive relative scale. A number on one of those scales is not automatically the percentage of water in drywall.

Ask for the meter model and mode, the material being tested, and the comparison used to interpret the result. If someone describes a maximum display as “100% wet,” ask what that means for that instrument. Do not convert it into an assumed amount of water or a repair cost.

Treat a thermal image as a lead to investigate

FLIR explains that thermal imaging identifies temperature patterns and that moisture findings need verification. A cold-colored area on an image is therefore a place to investigate, not a standalone picture of water inside a wall.

For example, imagine a cool rectangle beside a window after a leak. Ask what direct observations or measurements support the interpretation, whether adjacent areas were checked, and how the finding relates to the known water path. Save the image with that explanation instead of a caption that declares unseen damage.

Unusual readings need confirmation

Protimeter notes that metal can influence non-invasive readings. The practical question is whether the operator considered the surface and assembly, especially when one isolated location behaves differently from nearby areas.

You should not have to decide whether a hidden object caused the reading. Ask what confirming method was appropriate and whether any area remains inaccessible. If access would disturb finishes, discuss who would perform that work, what precautions apply, and how the opening would be repaired.

Keep a map that another person can understand

Give each location a simple identifier such as “hallway wall, point A” and connect it to a photograph or sketch. Ask the contractor to maintain comparable measurements when tracking progress. Keep original results alongside updates rather than replacing yesterday's record.

• Room and exact location of the measurement.
• Material or layer evaluated, including any depth information provided.
• Instrument and mode used.
• Date, result, and the technician's interpretation.
• Reference or target and why it is appropriate.
• Areas that were not evaluated and the planned next step.