Guide to the C555 Concrete Moisture Meter for Residential Use

Imagine getting a call from a customer a couple of weeks after you install a floor covering in their home. Their floors are warping—and they want to know why.

Or maybe it’s your dream home with floors that are warped, discolored, or releasing odors.

It’s exasperating—especially if you took the precautions to monitor moisture levels in your flooring materials and let them acclimate before installation.

What went wrong?

Whether you’re a residential flooring professional, an inspector, or a handy homeowner, you’re probably facing the same culprit: moisture issues in the concrete subfloor.

The damage can cost you time, money—and even your reputation.

That’s why monitoring and managing moisture in concrete subfloors is crucial to your flooring project. You want floors—whether hardwood, laminate, or carpet—that stand the test of time.

A moisture meter, like the C555 concrete moisture meter, can help you make that happen. It can help you locate leaks, detect wet spots for further testing, and determine if the environment is appropriate for concrete drying.

Let’s talk about:

• How the C555 Concrete Moisture Meter Works
• Why Measuring Concrete Moisture Matters
• The Benefits of Using a C555 Before Floor Installation
• Other Residential Uses for C555 Moisture Meter
• Customer Experiences Using the C555
• How to Set Your Projects Up for Success

First, what is the C555 moisture meter? Let’s break it down.

How the C555 Concrete Moisture Meter Works

Place the C555 on a smooth, flat concrete surface to take a concrete moisture reading.

The C555 handheld concrete moisture meter provides fast, non-destructive preliminary moisture measurements on smooth, firm concrete.

Here’s how it works to test a concrete floor for moisture with the C555:

1. Turn on the moisture meter.
2. Press the button for standard mode.
3. Place it on a smooth, concrete surface.
4. Get an instant moisture reading.

Like other concrete moisture meters on the market, the C555 reading tells you how much moisture the slab has within the top half-inch or so of concrete. This info helps you pinpoint problem areas quickly and over a large area, without the need to drill holes or drive pins into the slab.

To get the full picture of how much moisture still needs to work its way up from deep inside the slab, you’ll want to follow up your findings with relative humidity tests, like the Rapid RH® L6 Smart Sensors.

Some key features of the C555 concrete moisture meter include:

• Standard mode: This setting reads moisture in the top .5 inches of concrete within the 1% to 6.9% moisture reading range.
• Relative mode: This setting compares moisture in non-concrete applications like gypsum or drywall.
• Relative humidity and temperature mode: Built-in sensors measure ambient temperature and relative humidity.
• On-demand calibration platform: Comes with a separate device for field calibration—saving you time and money.

The C555 concrete moisture meter allows a person to follow the suggestions of the ASTM F2659 procedure for preliminary evaluation of moisture conditions. ASTM (the American Society for Testing and Materials) creates standards to guide professionals in each industry.

Now let’s talk more about why it’s crucial to perform moisture testing in concrete subfloors.

Why Concrete Moisture Testing Matters in Residential Flooring

Buckling like this is one of many kinds of moisture-related flooring issues.

The ASTM F2659-23 standard puts it like this:

“Moisture in concrete floor slabs affects the performance of flooring systems such as resilient, wood, and textile floor coverings and coatings.”¹

“Excessive moisture in floor slabs after installation can cause floor covering system failures such as delamination, bonding failure, deterioration of finish flooring and coatings, and microbial growth.”²

Now let’s cover some quick science behind why moisture can become an issue.

All concrete starts as a mix of water, cement, aggregates, and sometimes other additives. Water binds the other ingredients and causes the chemical reaction that hardens, or cures, the concrete over time.

Concrete usually cures enough to walk on within 24 to 48 hours. But concrete will continue to release excess moisture through the surface from deep inside the slab. This evaporation process continues until the concrete reaches the same humidity level as the air.

But if you install flooring before the slab releases enough moisture, it can cause:

1. Breakdown of flooring adhesives
2. Wood floor warping, cracking, shrinking, or crowning
3. Linoleum floor warping or discoloration
4. Vinyl floor buckling, swelling, or shifting
5. Growth of mold or mildew in carpet

Most of these issues cause unsightly and damaged floors. And that’s not ideal for residents or flooring professionals.

But mold growth impacts air quality. So, measuring moisture in slab before floor installation is not only crucial for floor integrity—but for the health of residents.

Many flooring manufacturers also require moisture testing before “the installation of coverings on floor slabs and screeds.”³ And not performing (and recording) moisture tests prior to floor installation can void the floor warranty.

Here’s the bottom line. Taking moisture readings in concrete subfloors can:

• Prevent flooring failures.
• Protect the health of homeowners.
• Track progress towards acceptable moisture content in concrete flooring.
• Save you time, money, and countless headaches.

Benefits of the C555 Concrete Moisture Meter for Floor Installation

Concrete moisture testing helps you track timelines for flooring installation.

You don’t need a Harvard scientist on hand to measure moisture. The C555 moisture meter makes it fast and easy to take average readings across your floor slab. And the intuitive, handheld design makes it ideal for residential flooring professionals, DIY enthusiasts, and homeowners alike.

The C555 takes readings without damaging existing structures and finishes. And it even has a high moisture alarm—so you can tell if you hit a wet spot without looking at the display.

With moisture readings, you can:

• Have a better understanding of which areas of your floor slab contain more moisture.
• Plan a rough timeline for floor installation.
• Promote faster drying (by increasing heat and lowering humidity, for example).

And in an ideal world (and timeframe), you can follow up by placing in-situ RH test probes in the hotspots to get accurate and specific moisture measurements.

But we get it. In the real world of residential flooring, in-situ testing isn’t always an option. And moisture meters are better than nothing.

Now let’s talk about how else you can use the C555 moisture meter in homes, apartments, and other living spaces.

Other Residential Uses for the C555 Moisture Meter

The C555 handheld meter does more than pinpoint which area of concrete still needs to dry the most. It can also:

• Find leaks
• Monitor ambient air
• Simplify quotes
• Inspect basements and crawl spaces

Let’s walk through each one.

The non-damaging nature of the C555 moisture meter makes it a go-to tool when providing quotes to potential customers. You can simply pull back a corner of the carpet and take a quick reading.

The C555 might help you get a better understanding of the environment that could be causing your floor slab to dry too slowly.

Concrete dries fastest in warm and dry environments. That’s why the C555 has integrated ambient temperature and RH sensors. They measure the surrounding air to let you know if you need to adjust the environment.

And FYI, making those adjustments can allow you to install your floors sooner.

Moisture meters like C555 also help if you’ve had flooding or suspect a leak.

That’s where relative mode comes in. In these cases, you’re not trying to find where to place probes in concrete. You’re measuring through other materials to see if one area reads higher than the rest—which could mean a possible leak, water damage, or mold growth.

This application also proves useful if you’re inspecting crawl spaces or basements. It can tell you if too much moisture is making its way in—and help you prevent costly surprises.

Now, let’s take a quick look at how some folks are stepping up their game with the C555.

Real-Life Experiences With the C555 Moisture Meter

The C555 also makes it easier to give accurate quotes to residential flooring customers.

One customer who goes by “Coach K” emphasizes how helpful it is to have the C555 moisture meter on hand for inspections:

“I am an inspector and use it to test the moisture content of concrete slabs mostly. I have used the Tramex meter in the past. This one is more affordable so I took a chance and am happy I did. I actually like the way it works better and the accuracy seems comparable. I would definitely recommend this meter.”

And Jeff B., from Garage Expressions, shares his use of the C555 in residential garages:

“We are a concrete coating company. Mainly garage floor coatings. And checking the moisture in the concrete is vital before selecting our primer coat to ensure permanent adhesion to concrete. Testing for moisture on every floor is vital to the success of our company and the Wagner C555 helps us achieve that.”

Think it’s worth adding to your toolkit?

Set Your Residential Flooring Projects Up for Success

Quality moisture meters prove useful to DIY enthusiasts, flooring professionals, and inspectors alike.

And one such meter, the C555 concrete moisture meter, makes it easy for those in residential construction or maintenance to:

1. Improve decision-making during floor installations.
2. Avoid costly repairs and replacements due to moisture-related floor damage.
3. Catch leaks and detect moisture from flood damage.
4. Perform preventative maintenance in moisture-prone areas.

By testing concrete moisture in residential flooring, you can have increased confidence that you’re creating a durable and healthy living environment.

And if you’re a flooring professional, it keeps you at the top of your game while protecting your time, money, and reputation.

It’s all about being proactive. Protect your home. Protect your business.

Shop Wagner Meter’s C555 Moisture Meter Today

Jason Spangler

Jason has 20+ years’ experience in sales and sales management in a spectrum of industries and has successfully launched a variety of products to the market, including the original Rapid RH® concrete moisture tests. He currently works with Wagner Meters as our Rapid RH® product sales manager.