(Editor's Note: This is the second installment of a series that examines building materials and the moisture meters needed for accurate measurements.)
Whether it's for a foundation, floor, or a thick wall, concrete delivers in ways other building materials can't.
Strong, durable, and long-lasting, concrete easily withstands the test of time and demands of use where other materials fall short. When was the last time you saw concrete with a termite problem or a wood floor in a manufacturing facility with extremely heavy equipment?
Despite its robustness, concrete is like any other building material in one respect -- it's susceptible to moisture issues. However, the same qualities that set concrete apart also provide challenges for assessing moisture within it.
Selecting the best moisture meter for concrete requires understanding the unique properties of this material and the various testing devices available (which might not be the meter you'd expect).
Concrete & Moisture: A Unique Relationship
At face value, it’s easy to think concrete is impervious to moisture. Rock solid and hard to damage, concrete would seem like an absolute barrier to everything.
However, this is simply not the case.
Despite appearances, concrete is actually rather porous -- especially uncured concrete. At a microscopic level, concrete’s makeup allows for moisture vapor to pass through it. You’ll see this especially in unsealed concrete floors because of their proximity to groundwater.
Compared to other materials, concrete can be deceiving when visually assessing for moisture. Because of its hardness and durability, what’s considered excessive moisture in concrete is very different from drywall or wood. In simplest terms, it takes a lot of moisture to create a noticeable issue with concrete. Like other materials, excessive moisture can lead to a range of problems in concrete, including:
- Reduced overall strength
- Cracking
- Spalling
- Mold growth
These issues are usually signs of a much bigger or moisture problem. What's more, other building materials nearby, e.g. a wooden baseboard or drywall, may also become affected by moisture that passes through concrete.
The Moisture Meter Needed for Concrete
Measuring moisture in concrete isn’t as simple as using your favorite professional moisture meter to take readings.
The best moisture meter for concrete isn’t a moisture meter. Rather, it’s a hygrometer with penetrating probes for in situ testing.
But first, let’s take a look at why professional moisture meters aren’t ideal for measuring moisture in concrete.
Both pin-type and pinless moisture meters are standard devices in a moisture inspector's toolbox. There's no question why -- while one measures actual moisture content and the other helps determine moisture's location, both work on a wide variety of materials.
With concrete, the story is a little different.
Though it’s possible to take moisture measurements in concrete with a pin-type meter, the readings are only valid to a certain extent. At best, a pin-type meter’s readings on concrete are quite literally surface-level and don’t account for vapor presence. Measurements with this meter type don't give a full assessment of moisture presence and shouldn’t be part of a final inspection report.
Pinless moisture meters (aka non-invasive moisture meters) are more useful when checking moisture in concrete. Their readings help determine moisture’s location and not its content percentage within the material. And like a pin-type meter, a pinless meter’s readings merit further investigation.
Before You Buy ...Pinless and pin-type moisture meters designed for taking measurements in concrete do exist. There are also meters marketed as “moisture meters for concrete floors,” too. However, be aware their measurements are as described above -- taken from the surface and not a true indication of moisture content within the material. In fact, their readings for concrete are not accepted by the ASTM. |
Back to hygrometers …
Hygrometer readings using the in situ method have been the go-to for moisture assessment in concrete for more than three decades. In fact, in situ moisture tests by the Technical University of Lund in Sweden led to creating of the ASTM F-2170, the standard for measuring moisture in concrete.
Providing the most accurate and reliable results for assessing moisture content within concrete, hygrometer in situ readings measure relative humidity (RH).
Unlike both types of moisture meters, hygrometer in situ readings don't rely on electrical conductivity or radio waves to take surface-level readings. Instead, hygrometer in situ readings are captured from inside a layer of concrete.
Below the surfaces of a concrete slab, in situ readings are not affected by factors such as condensation or humid environments, which can make for false-positive readings. Additionally, using multiple hygrometer probes during testing (a best practice) provides a more complete picture of moisture content and distribution within a concrete slab.
Those tests by the Technical University of Lund in Sweden – they found that moisture in concrete isn't uniform as it moves through a slab or floor at a gradient. Thus, using multiple probes helps accurately pinpoint moisture’s location and content percentage.
The Cut & Dry of Measuring Moisture in Concrete
When it comes to assessing moisture in concrete, hygrometer in situ readings are the go-to method. Taking moisture measurements in concrete using the in situ method is a relatively straightforward process.
Simplifying the in situ method, the process involves:
- Drill holes in the concrete being tested -- specifically three probes in a 1,000 square-foot area + one probe for each additional 1,000 square feet.
- Insert the probes, sealing them in with a cap.
- Wait 24 hours
- Record readings with a hygrometer
Want a more in-depth look at in situ readings?
Check out our flooring kit demonstration:
Concrete Moisture Meters: A Different Device for a Different Moisture Perspective
Though a standard building material, concrete requires a unique approach for moisture assessment.
While pinless and pin-type meters may have their uses in gauging and locating moisture in concrete, their readings are not a true indication of the material's moisture content.
Hygrometer in situ readings, on the other hand, provide the most accurate and reliable results for assessing moisture within concrete.
Did Our Flooring Kit Catch Your Eye?
Learn more about it and how it makes measuring moisture in concrete a breeze:
