Improved techniques make concrete testing easier

It wasn’t until the 15th of my 40 years in the industry that I had to seriously deal with the question of concrete moisture testing prior to floor covering installation.

Christopher Capobianco

I had spent my career on the residential side of the business, and it was not an issue that came up very often.

When it did, we taped a sheet of plastic to the concrete overnight to test. When I made the switch to the manufacturer side in 1992, I got a call in the office day one, asking what the requirements were for concrete moisture levels. I did a quick “let me get back to you” and called some people way smarter than me.

By the next year I had joined ASTM committee F.06 on resilient flooring to learn more about industry standards and wound up involved in creating the first two ASTM test methods for concrete moisture testing as a small part of a great group of concrete scientists, resilient flooring experts and manufacturers of testing equipment that created these documents and has been refining them ever since. I still am a proud member of that committee, although not as active as I once was. Recent changes to ASTM test methods make it easier to test concrete than ever before.

A lot of installers and dealers tell me they have never done concrete moisture testing, and “never had any problems.” I tell them they are lucky and ask them if they play the lottery. In the years that I have been inspecting floor covering failures as part of my job responsibilities, the results of moisture related failure have been pretty ugly in many cases; ugly floors and ugly, contentious, finger-pointing situations. Today, there is so much awareness of concrete and moisture testing among the design and construction community that nobody from architects to general contractors to installers can plead ignorance anymore. Luckily, methods have gotten easier and the results more accurate.

A light grinding of a 50 cm square is required to prepare concrete for ASTM F1869 Calcium Chloride testing.

The two commonly used tests are the calcium chloride test that became ASTM F1869* in 1998, and the ASTM F2170** relative humidity (RH) test that was published in 2002 and is widely thought of as the most accurate method. Both methods have always required a three or four-day process for test results. However, recent changes to ASTM F2170 have shortened that time to one day, which makes the whole process a lot easier.

By the way, the plastic sheet method that I mentioned earlier still gets used sometimes. The idea is that if the concrete beneath the plastic looks damp after a day or two, be concerned. However, this method does not give you a numerical value, so you can’t really make a plan for remediation. Plus, I saw firsthand a laboratory test where this method was done side by side with the other two methods and the plastic sheet was dry when the other two results were very high. That was an eye-opener that confirmed that we should not rely on plastic sheets to tell whether or not concrete is dry.

The calcium chloride test method has been around since the 1950s, and since 1998, our committee has done a lot of research and “round robin” testing to refine the ASTM F1869 method, right up to the most recent revisions in 2016. The result is a written test method that if followed will give the proper results. Three steps of F1869 that are often done incorrectly are the three day waiting period for results, the need to ”lightly grind an area 50 by 50 cm*” before placing the test and the necessity of testing when temperature and humidity conditions are the same as when the space will be occupied.

ASTM F2170 Relative Humidity Testing.

Missing these details makes the test invalid, so be sure to test completely “by the book,” meaning the 2016 version. ASTM F2170 measures inside the slab by drilling holes.

The 2018 version now has a 24 hour waiting time for the results, which is easier for everybody. The holes could be drilled first thing in the morning one day and the next day results can be
obtained. Other changes since F2170 was first published include the depth of the holes. Depending on the type of concrete slab and where is placed in the building, the holes are drilled to either 20 or 40 percent of the slab depth.

There also have been advances in the equipment for this testing.

RH testing devices that can be reused many times are great for people that do a lot of testing. Reusable probes are placed in holes and then a hand held meter is connected to get test results. The probes can be left in place or moved from hole to hole. The probes and meters are re-calibrated periodically to maintain their accuracy.

Another big advance was single use “all in one” devices that are placed in the holes for quick results. These also can be left there for long periods of time to monitor RH. This type of device tends to be less costly and easier to use for the people that don’t do a lot of testing. The real 21st century advance is RH testing equipment that can wirelessly connect to the Internet so the results can be monitored remotely. Talk about space age technology for floors!

Calcium chloride testing in progress. Courtesy of Independent Floor Testing And Inspections (IFTI).

I’m sure some of my readers are asking, “Why test?“ Or “when do we need to test?” I’ll answer the second question first.

ASTM F710*** is the industry standard for concrete testing and preparation. It says, “All concrete slabs shall be tested for moisture regardless of age or grade level.” The majority of manufacturers say the same. Always test.

ASTM F710 also says “although carpet tiles, carpet, wood flooring, coatings, films and paints are not specifically intended to be included in the category of resilient floor coverings, the procedures included in this practice may be useful for preparing concrete slabs to receive such finishes.” I would add patching/ underlayment compounds and even tile to the list. These standards are used throughout the industry.

Now, back to the question of “why test?” For starters, it’s a requirement for most every type of floor covering; if you don’t do it and there’s a failure related to moisture, it could fall completely on you. Second, it’s a profit centre. I don’t advocate doing moisture testing for free. The “book” requires it and it needs to be done, so if you do it, charge for it.

Truth is, most of the calls for concrete testing are on commercial jobs and new construction. I don’t see a lot of moisture testing being done on residential renovation projects. However, because it’s a lot easier to test now, you might want to think about it, especially on the high-end residential projects where the floor covering is expensive.

The cost of failure goes up as the cost of material goes up!

The bottom line is that if you present yourself as a professional floor coverer, moisture testing has to be part of your repertoire just as much as the products and the installation services you provide.

Christopher Capobianco has been in the floor covering industry since the 1970s in various roles including retail and commercial sales, technical support, consulting, journalism, education and volunteer work. He currently is part of the sales team for Spartan Surfaces in New York City. You can reach him via christopher@SpartanSurfaces.com.

* ASTM F1869, Standard Test Method for Measuring Moisture Vapor Emission Rate (MVER) of Concrete Subfloor Using Anhydrous Calcium Chloride
** ASTM F2170, Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using In Situ Probes.
***ASTM F710 Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring.
These documents are available from ASTM International.

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