I was inspecting a moisture intrusion on a large condominium project (over 100 units affected) following Hurricane Matthew, when the adjuster suggested, “If there is no visible water damage, don’t bother using your moisture meter.” My response: the main reason restorers utilize moisture meters is to identify otherwise visibly hidden moisture.
Why do we dry buildings? Generally, to re-establish a healthy environment and the property’s value. This work, however, comes with challenges, such as collecting payment and liability from improper work (e.g., microbial growth, structural deterioration, or associated health claims).
How do we demonstrate project completion? Primarily through the proper and documented use of moisture meters. “The restorer should establish drying goals that would be expected to inhibit microbial growth and return materials to an acceptable moisture level or content.” (ANSI/IICRC S500 2021 Standard for Professional Water Damage Restoration [hereafter S500] 188.8.131.52)
The S500 further states, “Restorers should be trained in the proper use and application of the meter … and have an understanding of the intended use, limitations, and proper operation of the device.” (S500 10.6.8). How often do technicians simply write down the numbers displayed without knowing what they mean or if they are accurate?
“Restorers should record and monitor relevant moisture readings daily” (S500 184.108.40.206). What happens in the coming weeks, months, or even years, when a dispute arises over payment, scope, or proper mitigation, and others are attempting to discredit your readings? Without moisture meter logs and proper documentation, what else would you have to prove your work?
Following are some considerations regarding moisture meters:
“Because differences in calibration occur from one instrument meter to another, restorers should … verify that the meters used are within a reasonable tolerance of each other…” (S500 10.9; 12.5.6)
Protimeter advises, “…The accuracy specifications of the product are valid for one year after the date of calibration, and the product requires recalibration after this period.” Delmhorst states, “With proper care and maintenance, the meter should stay in calibration;…”
Our meters get abused. They experience extreme temperatures, get dropped, and are dragged through muddy crawlspaces. As a result, we must verify calibration. Fortunately, a calibration test is a simple way to protect the integrity of your readings, or know if you need to send the meter in for factory re-calibration. Many meters have in-field calibration testing which can be done through an accessory or is built-in to the meter’s programming. This test could be performed at the beginning of each shift or job.
The S500 10.9 continues: “…A dedicated calibration device is a manufacturer-approved benchmark meter or calibration block.” Examples of this include:
- Delmhorst: “The MCS-1 can be used on any meter with a wood scale. With two electrical resistance values (12% and 22%) [within tolerance] to test your meter against,…”
- Protimeter: “Hold the Calcheck across the electrode pins as shown. A correctly calibrated [meter] will read 18.2 ±1.0….”[within tolerance]
- Tramex: “…a calibration check box is available…[which] allows for daily on-site calibration checks.”
Tip: On your daily moisture log, add a line and checkbox to confirm calibration was tested and verified.
Moisture Content vs. Moisture Level
(See the S500 definitions.)
The term moisture content is used with a meter calibrated for a specific material and temperature. For example, a meter calibrated for Douglas Fir wood at 68°F would be stated as 22% moisture content.
The term moisture level is the S500 recommended term when using a meter on a relative scale (not calibrated for a specific material). For example, a meter not calibrated for gypsum wallboard could be stated as having a moisture level of 88. The term “points” is often used instead of, or along with the word “level.” For example, a moisture level of 88 points or simply 88 points.
A pin-type meter always displays as a percentage. However, when used on a material the meter is not calibrated for, the reading would be moisture level (not moisture content). It would be based on a relative scale (requiring comparison to an unaffected area). This is sometimes referred to as Wood Moisture Equivalent (WME). For example, in this scenario, a pin-type reading displaying 47% could be documented as: using a pin-type meter, the material has a moisture level of 47 points.
Different Brands, Different Meters, Different Ranges
Relative readings are applicable when used comparatively against other qualitative readings of the same material. Each meter has a range that is determined by the manufacturer and varies between brands and meters.
The meter does not know if it is “reading” wood, drywall, concrete, plastic laminate, etc. It simply sends out a signal and then assigns a number. You could think of a gas gauge on a car. Having 1/8 of a tank of gas doesn’t tell us how many gallons are in the tank. And it will be a different number of gallons (or range) for a compact car or a large truck. A relative meter doesn’t tell us how much, but rather tells us where we are in relation to where we want to be (i.e., Dry Goal).
Some non-invasive relative meter ranges are as follows:
- Extech 1-99.9
- Flir 0-100
- Tramex 0-100
- Delmhorst 0-300
- Protimeter 60-999
Since they are comparative, the range used for each meter does not matter. What does matter is using the same meter on the job throughout the project. For instance, during the initial inspection, a Protimeter is used, (range of 60-999). The affected wet drywall reads 999 points, with the non-affected drywall (Dry Standard) at 100 points. On day two, a Tramex meter (range of 0-100) is used. The affected (still wet) drywall reads 100 points. Comparing this reading to the Dry Standard of 100 points it is determined the material is dry and equipment is removed. Mixing meter brands with different ranges could allow areas of the building to remain wet.
Additionally, relative readings cannot be converted to a moisture content reading or percentage. To illustrate, a non-invasive reading on a Delmhorst NavPro is 236 points would NOT be the same as 23.6% moisture content.
Meters can give false readings, positive or negative, resulting in unnecessary demolition of dry materials or not properly drying wet materials.
False or incomplete readings can result from:
- Metal in or behind materials (e.g., framing, foil-backed insulation, corner bead, plaster lathe)
- Surface water (e.g. condensation on wall finish; water on top of vinyl flooring)
- Pressure-treated lumber
- Air gaps (e.g., void space between unaffected drywall and wet insulation or between dry wood paneling and wet drywall)
- Using the wrong meter setting
- Concrete or floor coverings over concrete
- Moisture under bottom plates or sill plates due to limited access (e.g., length of electrodes)
Know Your Meters
Understand the specifics of the meter you are using. For instance, one manufacturer says the built-in pins should make firm contact with the surface, but it is not necessary to push the pins below the surface. In contrast, another instructs the pins be inserted into the material.
Using screws to extend meter pins into areas with limited access (e.g., under or into bottom plates)
Delmhorst recently shared research concluding that zinc or brass screws will yield a more accurate and consistent reading as opposed to stainless steel screws.
Many manufacturers state pin-type readings in wood should be taken with the pins parallel to the grain. (I know of moisture readings being thrown out of a court case because the individual who took the readings was unaware of this.)
Corrections (Species and Temperature) – Some meters are programmed to allow the restorer to select the type of material and the surface temperature, and the meter automatically makes the corrections. Other meters require the correction to be determined based on a temperature or species correction chart. ·
Restorers need to understand their readings to verify drying progress is occurring. Readings are so much more than a number written down just to go in the file. “When benchmarks are not being met towards an acceptable drying goal, the restorer should further investigate to identify the cause and take corrective action” (S500 220.127.116.11)
Tip: Read your user manuals.
Let’s Wrap This Up
Our restoration company received numerous requests through the years for our mitigation documentation relating to a home or commercial building that was being sold. The buyer was looking for reassurance that the disclosed water damage was resolved correctly and that their investment was protected.
I have also been retained to review others’ job documentation for property transactions. At times, proper documentation clearly shows the job was completed properly, which gives a level of comfort needed to proceed with the purchase. Other times, it is very poor and becomes an obstacle for the buyer and for the seller, who paid to have the work performed professionally to avoid this very situation.
I have experienced cases where restoration clients are involved in a dispute or litigation, which at times has ended almost as soon as it started due to excellent documentation. I have also seen a restoration firm have to pay out, not because of poor workmanship but because of insufficient or inaccurate documentation.
In a recent conversation with Delmhorst CEO Tom Laurenzi, regarding this article, I asked what his takeaway message would be. His response was, “As obvious as it may seem, users don’t always have the meter set to the correct scale (wood/species/material vs. reference scale or WME). As important as checking the calibration is, checking for the proper scale is critical.” This is a common theme among moisture meter manufacturers’ documentation and the source of many problems in the field.
Remember: Our job is not just to dry; but to dry and verify!