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Concrete Moisture Measurement Buying Guide

Investing in a concrete moisture meter is a crucial step towards ensuring the success of your next flooring project. Improper moisture levels in concrete slabs can lead to a host of problems after installation, including discoloration, warping, and even mold growth. These costly repairs can be easily avoided by using a reliable moisture meter to verify that the concrete has dried sufficiently before laying down floor coverings.

BlastOne offers a comprehensive selection of concrete moisture measurement instruments to suit any project need. The two most-common methods utilize non-destructive electronic impedance meters (ASTM F2659) or in situ relative humidity probes (ASTM F2170).

This guide will equip you with the knowledge to choose the perfect meter for your specific application. Prevent flooring system failure by inspection the moisture content of the concrete.

	Name	Best Scenarios	Benefits	Disadvantages	Options	Product Page
	PosiTest CMM	Fast & Non-Destructive Near-instant moisture readings without drilling Quick inspections Conforms to ASTM F2659	Simple Design. Simply placing the DeFelsko CMM directly on a clean, concrete floor gives a quick moisture measurement. It is a non-destructive test and doesn’t require holes to be drilled in the concrete slab or screed. Fast. The CMM gives instant readings. Robust. Sturdy IP65 construction offers weatherproof, dust proof, and water resistance. Shock resistant too! Easy to use. For large areas, the optional DeFelsko Telescopic Extender eliminates the need for kneeling to perform the tests. Capable. Tests concrete moisture to depths of ¾ or 1 inch. Integrates with PosiSoft software via USB cable for reporting.	Limited Depth Penetration: Unlike invasive methods, the PosiTest CMM only measures moisture in the shallower layers (up to 1 inche) of concrete. This may not be suitable for situations requiring deeper moisture assessment. Not Suitable for All Applications: While fast and convenient, the PosiTest CMM is best suited for quick, preliminary moisture evaluation. For highly critical projects or deep moisture readings, alternative methods might be necessary.	Integral Probe with Direct Contact Surface Temperature Sensor Integral Probe with Infrared Surface Temperature Sensor Integral Probe with K-type Cabled Surface Temperature Sensor Integral Probe with Wind Speed Sensor Cabled Probe with 1/2″ NPT Threads (for compressed air)
	PosiTector CMM IS	Highest level of testing accuracy Inserted into holes drilled into concrete Conforms to ASTM F2170	Simple Design. Individual In-Situ meters, inserted into holes drilled into concrete, connect wirelessly to the PosiTector App, or to a PosiTector Advanced Gage/DPM probe. Capable. The PosiTector CMMIS offers the most accurate moisture measurement in concrete as it detects moisture levels well below the floor surface. Configurable. With various expandable package options, the CMM IS platform can test on any size concrete floor. Long Lasting. Probe remains powered on for up to 3 weeks and broadcasts wirelessly via Bluetooth while in situ	Limited Depth Measurement: While convenient, in-situ probes like the CMM IS typically measure moisture content in the near-surface layers of concrete (around 1-2 inches). This may not be ideal if you need to assess moisture deeper within the slab. For situations requiring deeper readings, invasive methods might be necessary. Environmental Dependence: The accuracy of in-situ meters can be affected by relative humidity and temperature. A constant temperature must be maintained within the chamber for 24 hours prior to measurement. Cost: While not necessarily the most expensive tool, in-situ meters like the CMM IS can represent an additional investment compared to simpler non-electronic pin-type meters. Probe Placement: Improper placement of the probes can impact the accuracy of the readings. Following the manufacturer’s instructions and proper surface preparation are crucial for reliable results.	3 probe Basic Kit, including caps, probe sleeve extensions, calibration check chambers and other accessories required for testing. 5 probe Complete Kit, including all the above plus a carrying case and a vacuum tool for cleaning out the drilled holes. 5 Probe Pro Kit, combines a PosiTector Advanced Gage/DPM probe with the above Complete Kit.


	PosiTest CMM	PosiTector CMM IS
Best Scenarios	Fast & Non-Destructive Near-instant moisture readings without drilling Quick inspections Conforms to ASTM F2659	Highest level of testing accuracy Inserted into holes drilled into concrete Conforms to ASTM F2170
Benefits	Simple Design. Simply placing the DeFelsko CMM directly on a clean, concrete floor gives a quick moisture measurement. It is a non-destructive test and doesn’t require holes to be drilled in the concrete slab or screed. Fast. The CMM gives instant readings. Robust. Sturdy IP65 construction offers weatherproof, dust proof, and water resistance. Shock resistant too! Easy to use. For large areas, the optional DeFelsko Telescopic Extender eliminates the need for kneeling to perform the tests. Capable. Tests concrete moisture to depths of ¾ or 1 inch. Integrates with PosiSoft software via USB cable for reporting.	Simple Design. Individual In-Situ meters, inserted into holes drilled into concrete, connect wirelessly to the PosiTector App, or to a PosiTector Advanced Gage/DPM probe. Capable. The PosiTector CMMIS offers the most accurate moisture measurement in concrete as it detects moisture levels well below the floor surface. Configurable. With various expandable package options, the CMM IS platform can test on any size concrete floor. Long Lasting. Probe remains powered on for up to 3 weeks and broadcasts wirelessly via Bluetooth while in situ
Disadvantages	Limited Depth Penetration: Unlike invasive methods, the PosiTest CMM only measures moisture in the shallower layers (up to 1 inche) of concrete. This may not be suitable for situations requiring deeper moisture assessment. Not Suitable for All Applications: While fast and convenient, the PosiTest CMM is best suited for quick, preliminary moisture evaluation. For highly critical projects or deep moisture readings, alternative methods might be necessary.	Limited Depth Measurement: While convenient, in-situ probes like the CMM IS typically measure moisture content in the near-surface layers of concrete (around 1-2 inches). This may not be ideal if you need to assess moisture deeper within the slab. For situations requiring deeper readings, invasive methods might be necessary. Environmental Dependence: The accuracy of in-situ meters can be affected by relative humidity and temperature. A constant temperature must be maintained within the chamber for 24 hours prior to measurement. Cost: While not necessarily the most expensive tool, in-situ meters like the CMM IS can represent an additional investment compared to simpler non-electronic pin-type meters. Probe Placement: Improper placement of the probes can impact the accuracy of the readings. Following the manufacturer’s instructions and proper surface preparation are crucial for reliable results.
Options		3 probe Basic Kit, including caps, probe sleeve extensions, calibration check chambers and other accessories required for testing. 5 probe Complete Kit, including all the above plus a carrying case and a vacuum tool for cleaning out the drilled holes. 5 Probe Pro Kit, combines a PosiTector Advanced Gage/DPM probe with the above Complete Kit.

Concrete Moisture Measurement Videos

How to Measure Concrete Moisture with PosiTest CMM

Measuring Concrete Moisture with Positector CMM IS

Why is Moisture in Concrete Measured?

Concrete is a composite building material comprised of an aggregate that bonds with a binding agent. Usually, the aggregate is a mix of crushed rock, granite, limestone, and sand. The binding agent is most commonly Portland cement. When mixing concrete, water must be added to create a workable mix, and to allow the cement to hydrate and cure. After hardening, much of this water remains as moisture within the porous concrete slab. Over the following weeks and months, this moisture is slowly emitted from the concrete until it eventually equalizes with the surrounding moisture levels.

This trapped moisture can cause major problems if flooring is installed too soon. Imagine: discoloration, warping, even mold growth! These costly repairs can be avoided by measuring the concrete’s moisture content before laying down any flooring.

6113d69d18f82f41ab45ba6e_Water-Damaged-Wood-and-Concrete-Floors

Water-damaged hardwood and coated concrete floors

Excess moisture trapped beneath flooring leads to issues like:

Even older concrete can have moisture problems if a vapor barrier (moisture barrier) is missing or damaged, allowing moisture to rise from the ground and saturate the concrete.

Moisture Measurements:

Concrete moisture meters measure various aspects like:

Moisture content percentage
Relative humidity (%RH)
Moisture vapor emission rate (MVER)

These measurements help determine if a concrete slab is dry enough for flooring installation. Improper moisture readings can lead to flooring failure down the road. ASTM F2170 and ASTM F2659, along with other standards, were created to determine the likelihood of issues resulting from excessive moisture levels in concrete.

How is Concrete Moisture Measured?

Non-Destructive Concrete Moisture Meters

Non-destructive concrete moisture meters, like the PosiTest CMM, can provide a near-instant reading of moisture content. Using the principle of electrical impedance, an alternating electric field flows from the device’s transmitting sensor pins through the substrate and is captured by the receiving electrodes. The impedance (or resistance) is measured. Increasing concrete moisture causes an increase in the impedance reading. Using concrete standards with known moisture levels, the meter can be calibrated to read in units of concrete moisture.

Pros and Cons of Non-Destructive Meters:

Fast and Easy: These meters offer a quick and convenient way to assess moisture without drilling into the concrete.
Limitations: However, their accuracy can be affected by factors like variations in concrete composition or the presence of metal reinforcement, such as rebar, close to the surface.
Depth: Concerete moisture meters only measure moisture near the surface, potentially missing high moisture levels deeper within the slab.

Ideal for Spot Checks:

Given these limitations, ASTM F2659 recommends using non-destructive meters for pinpointing areas with potentially high moisture content, rather than definitive moisture readings.

Learn More:

For a deeper dive into non-destructive moisture measurement with the PosiTest CMM, check out our video or article: “How to Non-Destructively Test the Moisture Content of Concrete Slabs”.

In Situ Concrete Relative Humidity Probes

For the most accurate measurement of moisture throughout a concrete slab, in-situ relative humidity probes are preferred. These probes, following the ASTM F2170 standard, involve drilling a small hole (around 40% of the slab’s depth) and inserting a specialized probe like the PosiTector CMM IS. This probe then directly measures the relative humidity within the concrete, providing a more accurate measurement of moisture levels compared to surface methods.

Precise Readings for Floor-Ready Concrete:

In-Situ probes go a step further, offering the most accurate moisture readings. To properly use the probe, a 3/4″ wide hole must be drilled into the concrete. The In-Situ probe is then placed in the whole, allowing the probe to acclimate to the environmental conditions for at least 24 hours.

Once the 24 hour period has passed, moisture testing can begin. The PosiTector CMM IS probes and free mobile app guide users through the ASTM F2170 documentation criteria.

Features:

Simple & Convenient: Effortlessly collect and report relative humidity (RH) readings following ASTM F2170. Probes stay powered for weeks, broadcasting data wirelessly via Bluetooth. No need to open holes or remove caps!
Accurate & Reliable: Rapid response precision probes deliver consistent, dependable readings. Automatic calibration checks ensure accuracy, and NIST traceable calibration certificates are included.
Durable & Reusable: Smart probes resist solvents, acids, oil, water, and dust – built to last. They’re backed by a two-year warranty.
Powerful & Efficient: Fast acclimation reduces testing time. Blue LED confirms operation, and the free mobile app streamlines data analysis and reporting.

Alternative Methods for Concrete Moisture Measurement

While there are other methods for checking concrete moisture content, like the calcium chloride test (ASTM F1869) or the plastic sheet method (ASTM D4263), these approaches are often less precise or time-consuming. For instance, the calcium carbide method (ASTM D4944, MilSpec CRD-C154-77) has fallen out of favor due to safety concerns.

For the most reliable results, consider the in-situ probe or non-destructive meter methods described earlier.

Anhydrous Calcium Chloride Moisture Tests

ASTM F1869

The Anhydrous Calcium Chloride Moisture Test offers a budget-friendly and user-friendly way to assess moisture levels in concrete. It works by measuring the weight gain of calcium chloride after it absorbs moisture from a sealed area on the concrete surface. An increase in weight gain indicates higher moisture content.

While simple to use and inexpensive, there are some drawbacks to consider:

Limited Depth: This test only measures moisture near the surface, potentially missing moisture deeper within the slab.
Wait Time: Results typically take 24 hours, delaying project timelines.
Accuracy Concerns: These kits cannot be realistically calibrated and can be influenced by ambient conditions.

Plastic Sheet Method

ASTM D4263

The plastic sheet method is a quick way to see if there’s active moisture near the concrete surface. It involves sealing a plastic sheet onto the concrete and checking for condensation buildup after a certain time.

While it’s not a precise measurement:

It can’t tell you the exact moisture level.
It’s easily affected by surrounding conditions like temperature and humidity.

What it can tell you:

If there’s condensation present, it suggests the concrete might still be releasing moisture and isn’t ready for most floor coverings.

Calcium Carbide Method

ASTM D4944

While the calcium carbide method offers accurate moisture readings, its drawbacks make it less suitable for most jobsites. Here’s why:

Destructive Testing: It requires taking concrete samples, damaging the slab itself.
Complex Setup: The test involves specialized equipment and expertise for proper execution.
Safety Concerns: Calcium carbide reacts with water to produce acetylene gas, which is flammable and requires careful handling.

Often times, it is best for this method to be performed in a laboratory using samples destructively collected from the jobsite.

Choosing the Right Method to Measure Moisture in Different Concrete Layers

Choosing the Right Tool for Your Needs

The best concrete moisture meter for your project depends on how deep you need to measure. Here’s a breakdown of the three most common methods:

Calcium Chloride Test (ASTM F1869): This simple test measures moisture vapor emission rate (MVER) from the surface, typically reaching only the top ½ to ¾ inch.

In-Situ Probes (ASTM F2170): PosiTector CMM IS. In the illustration below, the slab is representative of being 6 inches thick and being dried on one side. 40% of 6 inches is 2.4 inches.

Measure at 40% depth of a concrete slab that is being dried from one side
20% depth of a concrete slab that is drying from two sides.

Non-Destructive Meters (ASTM F2659): These convenient meters, such as the PosiTest CMM, offer quick readings but typically only measure down to ¾ to 1 inch from the surface.

611189885da99f091df1cc2a_Concrete-Cross-Section-And-Standards-Comparison-1200x675

Illustration depicting the general depth in a concrete slab that anhydrous calcium chloride tests, in situ relative humidity probes, and non-destructive electrical impedance meters measure the moisture condition

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Concrete Moisture Test Standards

The following standards are used to determine the moisture content and moisture condition within a concrete or screed slab:

ASTM Adhesion Testing Standards

ASTM F2659—Standard Guide for Preliminary Evaluation of Comparative Moisture Condition of Concrete, Gypsum Cement and Other Floor Slabs and Screeds Using a Non-Destructive Electronic Moisture Meter
Related product: PosiTest CMM

The outlines and procedures within ASTM F2659 guide the user through conducting relativistic moisture tests with an electrical impedance meter. It defines proper ambient conditions and preparatory tasks to be completed before performing the measurements.*†

“5.1 Moisture in concrete floor slabs affects the performance of flooring systems such as resilient, wood, and textile floor coverings and coatings. Manufacturers of such systems generally require moisture testing be performed before installation of coverings on floor slabs and screeds. The measurement of sub-surface comparative moisture condition in the upper 1.0 in. (25.4 mm) stratum of a concrete slab with a non-destructive moisture meter is one such method.”

While the moisture condition within the top 1 inch may be determined by an electrical impedance meter, absolute moisture content as well as “equilibrium” within the slab is not determinable. ASTM F2659 recommends, “Where possible, or when results need to be quantified use this standard guide to determine where additional testing such as Test Methods F1869, F2170, or F2420 as specified to characterize the floor slab and the test area environment for moisture, humidity and temperature conditions.” Electrical impedance meters as described in ASTM F2659 are ideal for creating a general understanding of the moisture condition within a slab and indicating where more in-depth, quantifiable tests should be performed.

*Refer to ASTM F2659 for a complete description of the method

†Moisture content requirements are often specified by flooring manufacturers. It is strongly recommended that the user refer to these to determine proper moisture conditions before installation of a flooring system.
ASTM F2170—Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes
Related product: PosiTest CMM IS

In situ concrete moisture (RH) probes—such as the PosiTector CMM IS—described in ASTM F2170 are designed to determine % RH (relative humidity) within a concrete slab. With the limitation of anhydrous calcium chloride tests and impedance meters only measuring the moisture condition within the top 1 inch of a concrete slab, a full understanding of absolute moisture content has been impossible with those methods.

“5.1 Excessive moisture in floor slabs after floor covering has been installed can cause floor covering system failures such as debonding, peaking and deterioration of finish flooring and coatings and microbial growth.

5.2 Manufacturers of such systems generally require moisture testing to be performed before installation on concrete. Internal relative humidity testing is one such method.”

ASTM F2170 addresses these issues and is considered to be the reliable and preferred method for determining the moisture condition within a new concrete slab. By drilling a hole to 40% of maximum slab depth* and placing the probe directly into the slab, an isolated chamber is created allowing for very targeted testing within the slab.

“ASTM F2170 requires 3 probes for the first 1,000 ft2 (100 m2) and another probe for each additional 1,000 ft2 (100 m2). One test must be performed within 3 ft (1 m) of each exterior wall.”* To identify additional locations for the in situ probes, consider using an impedance meter as described in ASTM F2659, such as the PosiTest CMM to detect areas of increased moisture content.†

*Refer to ASTM F2170 for a complete description of the method

†% relative humidity requirements are often specified by flooring manufacturers. It is strongly recommended that the user refer to these to determine proper moisture conditions before installation of a flooring system.
ASTM F1869—Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride
The Anhydrous Calcium Chloride method seeks to determine the rate of emissivity of water from concrete slabs—an indication of capillary action or “movement of water”. Once MVER (moisture vapor emission rate) is measured per ASTM F1869, determination to install a flooring system may take place.*†

“4.1 Use this test method to obtain a quantitative value indicating the rate of moisture vapor emission from the surface of a concrete floor and whether or not that floor is acceptable to receive resilient floor covering.”

While the standard purports to indicate when satisfactory moisture conditions within a concrete slab are existent, significant doubt about the accuracy and effectiveness of these determinations exists. Ambient conditions above the slab will often dictate the results of the test, as well as surface preparation, and whether the tests are performed on-, above-, or below-grade. It is often recommended to use several test methods to give a better understanding of the actual moisture condition within the concrete.

*Refer to ASTM F1869 for a complete description of the method

†MVER requirements are often specified by flooring manufacturers. It is strongly recommended that the user refer to these to determine proper moisture conditions before installation of a flooring system.
ASTM D4263—Standard Test Method for Indicating Moisture in Concrete by the Plastic Sheet Method
ASTM D4263 outlines the use of an 18 x 18 inch (45.7 x 45.7 cm) sheet of polyethylene plastic, stretched taught and taped (sealed) to the surface of a concrete slab. After 16 hours, the inspector removes the plastic and identifies if moisture is present on either the plastic sheet or the underlying concrete.*†

While this method may indicate that there is a potential issue, quantifiable determination of the moisture present is not possible. Results are strongly dependent on the ambient conditions of the location, so there may be issues present with little sign provided by this test. It is not recommended to be used as a stand-alone determination.

*Refer to ASTM D4263 for a complete description of the method

†Actual or absolute moisture content may not be readily apparent with this method. It is strongly recommended that the user consult the flooring manufacturer’s recommendations for acceptable test procedures and moisture levels.
MilSpec CRD-C154-77—Standard Test Method For Determination Of Moisture In Fine Aggregate For Concrete By Means Of A Calcium-Carbide Gas Pressure Meter
The MilSpec CRD-C154-77 standard guides the user through the calcium-carbide method of determining moisture content of a concrete or screed slab. It requires the use of a pressure chamber and gage to measure the reaction of combining calcium carbide and a sample of the concrete or screed slab.*†

“1.1 This method of test is intended to determine the moisture content of fine aggregate for concrete by means of a calcium-carbide gas pressure moisture tester.”

The calcium carbide method of determining concrete moisture is considered to be a highly accurate method, though there are some considerations. It is a destructive test and when measuring over large areas may require a considerable amount of time to measure all samples. It produces acetylene gas, which may be prohibitive on some job sites. The calcium carbide reagent is a consumable and will add additional costs over the long term. Being a non-digital testing procedure, recording test results and building reports can be more time intensive. Lastly, it is a very sensitive test that requires stringently controlled testing conditions to provide accurate results and should not be relied upon by untrained personnel.

ASTM offers a calcium carbide testing method (ASTM D4944), but it is specified for use in testing soils, not concrete or screed aggregates.

*Refer to MilSpec CRD-C154-77 for a complete description of the method

†It is strongly recommended that the user consult the flooring manufacturer’s recommendations for acceptable test procedures and moisture levels.
ASTM F710—Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring
ASTM F710 is not specifically a guide to concrete moisture testing, but a holistic practice used to establish suitability of a concrete slab to receive a resilient flooring system.

“1.1 This practice covers the determination of the acceptability of a concrete floor for the installation of resilient flooring.”

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Concrete Moisture Measurement Buying Guide

Concrete Moisture Measurement Videos

How to Measure Concrete Moisture with PosiTest CMM

Measuring Concrete Moisture with Positector CMM IS

Why is Moisture in Concrete Measured?

Discoloration

Cupping (edges curling upwards)

Buckling (uneven surface)

Blistering (raised, bubbled areas)

Adhesive failure (flooring detaching)

Mold growth

Moisture Measurements:

Moisture content percentage

Relative humidity (%RH)

Moisture vapor emission rate (MVER)

How is Concrete Moisture Measured?

Non-Destructive Concrete Moisture Meters

In Situ Concrete Relative Humidity Probes

Alternative Methods for Concrete Moisture Measurement

Anhydrous Calcium Chloride Moisture Tests

Plastic Sheet Method

Calcium Carbide Method

Choosing the Right Method to Measure Moisture in Different Concrete Layers

Choosing the Right Tool for Your Needs

WANT TO STREAMLINE YOUR NEXT PROJECT?

Concrete Moisture Test Standards

ASTM Adhesion Testing Standards

ASTM F2659—Standard Guide for Preliminary Evaluation of Comparative Moisture Condition of Concrete, Gypsum Cement and Other Floor Slabs and Screeds Using a Non-Destructive Electronic Moisture Meter

ASTM F2170—Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes

ASTM F1869—Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride

ASTM D4263—Standard Test Method for Indicating Moisture in Concrete by the Plastic Sheet Method

MilSpec CRD-C154-77—Standard Test Method For Determination Of Moisture In Fine Aggregate For Concrete By Means Of A Calcium-Carbide Gas Pressure Meter

ASTM F710—Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring

Frequently Asked Questions

Is the PosiTest CMM calibrated at the factory?

How does the PosiTest CMM differ from the PosiTector CMM IS?

Why is concrete moisture measurement important?

How many readings can the PosiTest CMM store into memory?

What information does the PosiTest CMM store into memory?

What are the different measurement scales available for the PosiTest CMM?

What are the different measurement modes available for the PosiTest CMM?

How long do the batteries last in the PosiTest CMM?

How is the PosiTest CMM checked for accurate operation?

Why test for moisture in concrete floor slabs?

How often should the PosiTest CMM be recertified?

Is reporting software available for the PosiTest CMM?

What is an in situ concrete moisture meter?

How is the PosiTector CMM IS different than other in situ instruments?

How do I view my PosiTector CMM IS readings?

How should I store the PosiTector CMM IS probes when not in use?

Does temperature affect relative humidity readings within the Calibration Check Chamber?

How long do the batteries typically last in the PosiTector CMM IS?

How are the PosiTector CMM IS probes calibrated at DeFelsko?

How long is the warranty on the PosiTector CMM IS probe?

What is the cost to recertify the PosiTector CMM IS probes?

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