Moisture Meters and Testing: Manufacturer Roundtable
Moisture continues to be a prevalent issue in the industry, and one of the best ways to counter this is to be prepared. That includes having a conversation with your customer beforehand about any potential moisture tests or mitigation that may need to be done. It also includes having the right tools to measure site conditions. To that point, we asked several moisture meter manufacturers to weigh in on the accepted industry tests, what they measure, how to interpret the results and some of the products they recommend.
Our panelists are: Tom Laurenzi, president of Delmhorst Instrument Co.; Grete Heimerdinger, vice president of Lignomat; Jason Spangler, Rapid RH product sales manager for Wagner Meters; and Richard Wexler, director of marketing, instruments, for FLIR.
Q: The two most common moisture tests involve calcium chloride and in-situ probes. What does each measure, when should you choose one over the other, and what do the results mean?
Laurenzi: Calcium chloride (ASTM F1869) is used to determine the moisture vapor emission rate (MVER) in a concrete floor slab. The test requires placing a small dish of calcium chloride on the slab, under a sealed plastic cover or dome. The salt absorbs moisture captured under the dome. After 72 hours the moisture vapor emission is determined by calculating the weight gain of the calcium chloride.
The test is easy to perform and carries a very low investment in equipment. Although it is specified by many adhesive and floor product manufacturers, it may not be suited for all applications. The test results are affected by ambient conditions, variations in surface prep, and the test is indicative of snapshot conditions only at the top 1/4 to 3/4 in. depth of the slab.
In-situ (ASTM F2170) testing is widely accepted in the industry as the most accurate and reliable test method to determine a slab’s readiness to accept a floor covering. The reason is that the test is depth specific: 40% of the slab thickness for slab on grade, 20% of the thickness for a slab drying from top and bottom. Relative humidity (RH) readings at these levels are not generally affected by ambient conditions and have been shown to be an excellent predictor of how a slab will behave after it has come into equilibrium with a floor covering installed. An added benefit for all parties is recent ASTM testing that has resulted in shortening the wait time for test hole equilibration from 72 to 24 hours.
If only one test can be performed, it may very well be F2170. However, the best outcomes (and often the least costly) occur when a combination of tests are performed to gain an understanding of the overall slab and environmental conditions.
Heimerdinger: Which test to perform will be decided by the requirements in the floor manufacturer’s warranty. In some cases the manufacturer may require both. The calcium chloride test reflects the condition of the floor close to the surface, whereas the in-situ RH probe test reflects the condition inside the concrete slab. Both are important since any adhesive applied reacts at first to the surface moisture. The floor covering installed will react later when any excess moisture from the core of the slab travels to the surface, after the surface is closed off by the floor covering or epoxy.
It is important to find out whether or not there is excess moisture in the mid-section of an open slab. Once the slab is covered, any excess moisture will be distributed evenly within the slab. This increase in moisture close to the surface can cause problems with epoxy, adhesives and floor coverings.
The in-situ probes reach deep enough to measure moisture levels in the mid-section of the slab. The calcium chloride test (and handheld meters) only measure moisture close to the surface. Handheld meters can still be used to give qualitative results of high and low, but they should not be used to determine if a floor covering can be installed.
Spangler: The calcium chloride test measures the amount of vapor emission, calculated over a 24-hour period. With this surface test, it is only looking at the vapor emission from the top 3/4 in. of the slab. In situ testing is measuring the RH% level within the slab. This depth-specific measurement is the RH% which will reach the surface of the concrete once there is a low permeable finish installed.
The easiest, most non-scientific way I put it to people (especially installers) is this: “Do you care about what is happening right this moment in the top 3/4 in. of the slab, or do you care about what is going to happen on the surface once all of the time, effort, and money has been expended to install a finish and a minimum 12-month workmanship warranty is in effect?”
Q: Both pin and pinless moisture meters are utilized for determining moisture in hardwood floors. What do each measure, when should you choose one over the other, and what do the results mean?
Laurenzi: Pin-type meters work on the principle of electrical resistance. Two electrodes (pins) are inserted into the wood and a small electrical current is passed between them. The amount of resistance correlates to the amount of moisture in the area between the two pins. The relation between wood and moisture is effective because wood is an excellent insulator and moisture is a good conductor, so higher moisture levels are the result of lower resistance. In this way the moisture level (below fiber saturation point) can be quantified.
The key to finding hidden moisture in a floor or subfloor is to use an electrode with pins that are insulated except at the tip. This allows you to test the conditions at different levels of penetration. Generally speaking, either a pin-type or pinless moisture meter can be used prior to installation, but a pin-type meter with insulated pins must be used after installation for troubleshooting or if investigating a claim.
Pinless meters emit radio waves into the material (wood) that are affected by the presence of moisture in the material. The characteristics of the returning waves determines the amount of moisture and is displayed as a relative or quantitative moisture content (MC) reading. To quickly identify wet areas, a pinless moisture meter is convenient and easy to use.
Pinless meters are excellent tools to help determine if further testing is required in certain areas. A pinless moisture meter may also be used to determine if waterborne finishes are dry and ready for a second application. These meters are susceptible to surface moisture, and are also influenced by materials below a 3/4 in. depth.
Heimerdinger: Moisture meters in the flooring industry are used to measure the subfloor and the hardwood floor planks. Pin meters measure the precise area between the pins. The pins can be placed very accurately where the user wants to measure. If Teflon-coated pins are used even an installed subfloor can be measured precisely without including the floor planks above or the concrete underneath. Talking about prices, pin meters are in general less expensive. However, they are cumbersome to use—especially in hard floor planks—and they leave pin holes.
Pinless meters measure a much larger area than pin meters and indicate one moisture percentage. This one number is an average of the measuring field. Dual-depth pin meters still give an average of the measuring field, only the measured fields are different. One is a shallow field close to the surface and one includes more material, but still produces an average of the measured field.
In the floor industry with most of the floors only being 3/4 in. thick, it is important that the pinless meter is calibrated for that thickness, otherwise measurements are not accurate. When dealing with dried out floors coming from low humidity in the air, some pinless meters (such as the Scanners from Lignomat) are able to measure very low moisture levels, where pin meters will default and cannot produce readings.
When inspecting a moisture problem of a damaged floor, the inspector is served well when using both types of meters. For a thorough look down into the floor, he should use the pin meter. For a fast glance across the floor he should use the pinless meter.
Ideally, both types of meters should be in the tool bag. Then the installer has a choice for the best suited meter for the task on hand. Most manufacturer making pin and pinless meters offer combination meters with measuring modes for both pin and pinless.
Spangler: Both types of technology measure the moisture content percentage of wood. Pin meters tend to be more effective in areas where the wood is either cupped, crowned, has excessive surface variations or the wood is very narrow. Pinless meters are most effective where the meter can lay flat on the surface of the wood being measured and where leaving pin holes isn’t an option.
When measuring the finished wood flooring and subflooring, the moisture content can be compared to the interior conditions to ensure proper acclimation of each and then compared against each other to ensure the measurements are within the given National Wood Flooring Association (NWFA) guidelines prior to installation.
Wexler: For hardwood flooring, today’s available pinless meters are the way to go. With pinless meters, installers are never concerned about damage from pin marks. Either with a flat panel for placing on wood, or with a spherical “ball sensor,” pinless meters allow readings that reflect moisture content deeper in the wood, up to 3/4 in. This can be useful for evaluating overall condition of wood moisture.
On the other hand, pin meters are useful for surface moisture conditions. Together, they are useful for getting a big picture of immediate surface conditions for surface prep work, and for getting a longer term view of the wood’s content overall.
Q: Can you tell us about your latest moisture meters and testing equipment?
Laurenzi: Our HT-4000F/PKG is a great value that reflects Delmhorst’s very low cost per test pricing for anyone performing in-situ testing.
Heimerdinger: Lately we have been promoting the dual-mode meter Ligno-DuoTec BW. It is not totally new, but a very important instrument since it measures moisture content in the pinless mode and with an additional accessory you can convert the meter into a thermo-hygrometer.
Our newest product is our data logger which records important information for the floor installer and floor user. The graph shows changes for days, months or years; RH; ambient temperature; EMC (equilibrium moisture content); and three independent measurements of wood moisture. It is the best tool to see how the moisture content is influenced by RH over a long period of time.
The equipment consists of a data logger—which can by itself record RH and temperature—and an add-on MC Tracker, which serves as three moisture meters measuring continuously.
Spangler: We have launched five new non-invasive wood moisture meters in the Orion family of meters. The 910 and 920 are single depth measuring meters with the 910 measuring at 3/4 in. depth and the 920 measuring at 1/4 in. depth.
The 930 model gives the user the option to measure at both 3/4 in. and 1/4 in. in one meter. The 940 has dual depth capability with the ability to store readings within the meter. The 950 offers an onboard relative humidity sensor that allows the user to measure the ambient RH and temperature, using this information to calculate dew point or EMC.
On top of this, the 950 is also Bluetooth-capable allowing it to integrate with two different smart device apps—FloorSmart and Woodshop MC—that help better document job-specific moisture content measurements. With every Orion the user receives a meter-specific, matched calibration block that allow for true on-site calibration. As with our previous line of meters, Wagner is still offering the best in class seven-year warranty.
Wexler: Our newest moisture meters add an innovative new dimension to moisture measurement with the addition of a compact thermal imager built right into the meter. Thermal imagers have been invaluable in the disaster and water damage restoration business since they instantly and visually reveal temperature variations due to moisture content in building materials.
For flooring, this can be useful to get a relative indicator of drying and curing process of building materials so that fans or ventilation can be targeted to slower drying areas. Thermal can be invaluable for documenting before flooring is installed that conditions were optimal, in case other factors intervene after an installation to cause a failure. From a troubleshooting perspective, a flooring professional can identify whether a structure has other factors to consider such as water intrusion or absent/failed insulation that will impact flooring due to temperature or heating fluctuations.
The FLIR MR176 offers a view into the next generation of multi-function moisture meters that also perform thermal imaging, together with added environmental measurements for temperature and humidity.
Also available are the FLIR MR59 Ball Probe Moisture Meter (Pinless) and FLIR MR55 Pin Moisture Meter.