10 Guidelines for ASTM F2170 Preparation and Testing

Construction crew

For flooring and concrete professionals, ASTM F2170 provides the standard for using relative humidity (RH) testing when measuring moisture content in concrete slabs. Meeting this standard provides the groundwork for limiting moisture-related flooring problems and the many liabilities and mitigation problems that can result from excess moisture.

The standard provides precise guidelines for RH testing methods. While any professional must understand the exact requirements of standard F2170 (the most recent version), the following are 10 guidelines to help ensure that you have met the criteria laid out in ASTM F2170. These requirements for the standard apply regardless of the RH test method being used.


  1. Confirm your test method equipment meets specifications. ASTM F2170 provides precise dimensions and requirements for accurate RH testing (section 6). Each hole must have a liner that isolates the sensor from ambient conditions, and sensors must have NIST-traceable calibration. Some calibration restrictions may apply, so read the standard carefully to be sure your test equipment qualifies for the most recent standard.
  2. Make sure your calibration is up to date. Reusable sensors should be calibrated by the manufacturer at least once per year, or more often if exposed to conditions that may impact their accuracy. All sensors must be calibrated no less than 30 days prior to use.
  3. Check job site conditions. Section 9 of the standard requires that both the slab and the ambient air above it must be at service conditions for a minimum of 48 hours before testing.
  4. Map your sensor count and location. F2170 requires three test holes for the first 1000 ft2 and, at least, one additional hole for each additional 1000 ft2. The total area of the slab and the number of test holes must be recorded on your report.
  5. Know the required depth of the test holes.40% Depth The test hole depth is not a fixed depth, but it must be calculated based on slab thickness and number of drying sides: 40% of the slab thickness if it is drying from one side only, or 20% of the slab thickness if it is drying from two sides. The depth is calculated to the bottom of the test hole (the location of the installed RH sensor or probe). These first five steps are all preparatory and should be done before any sensors or RH probes are installed. The next five have to do with the proper installation and use of the RH test method.

RH Testing and Reporting

  1. Drill and prepare the test holes. Each test hole must be drilled to the depth determined at Step 5 above (section 10 of ASTM F2170) and properly prepared. For most RH testing systems, this includes cleaning any debris out of the test hole and inserting the necessary liner in the hole. Note that the liner requirements have been updated and the hole is to be fully lined to meet the ASTM standard.
  2. Insert RH sensor. Follow the manufacturer’s directions for inserting sensors into each test hole. If using the Rapid RH®, each Smart Sensor™ should be inserted in the test hole and will remain in position for the duration of testing. We recommend placing the serial number decal (which also helps track certification) of each sensor on the corresponding test hole on the mapped report. Each hole should be capped and sealed according to the manufacturer’s directions during equilibration.
  3. Equilibrate sensors for 72 hours 24 hours before initial reading.Wait 24 Hours ASTM F2170 requires each sensor to equilibrate at least 72 hours now only 24 hours before a documentable reading is recorded. As a practical matter (not a compliance matter), the Rapid RH® has been shown to provide readings within 3% of the final RH value within 1 hour of sensor insertion. This will NOT be valid for ASTM compliance, but can certainly provide a target timeline for schedule decisions or for choosing alternate adhesive or flooring options that might have higher moisture tolerances.
  4. Take RH readings. After the 72-hour  now only 24-hour equilibration time frame, an initial reading should be recorded for each sensor. In addition to the RH value, verify too that the reading does not drift more than 1% over a 5-minute period. After the initial reading, readings can be updated at any time desired with two conditions in mind: If using reusable sensors, each sensor must equilibrate a minimum of one hour in each test hole before taking a reading; or, if using the Rapid RH®, readings can be taken immediately because the sensor remains installed in the test hole and is therefore fully equilibrated at all times.
  5. Use our checklist to record and report the RH readings. Section 11 of ASTM F2170 details the requirements of each report, including test hole location, dates and times of measurements, RH reading, temperature reading, and any other conditions that might impact the RH reading (see section 11 for complete reporting requirements). With all areas of ASTM-compliant RH testing, precision is key and data integrity must also be the focus for each flooring professional. Wagner Meters’ DataMaster™ L6 app provides wireless recording and storage of RH data for each job site as well as certifiable reporting through the website at www.f2170reports.com. As any professional knows, ASTM standards are established to help guide industry testing and also to help ensure standardized best practices to protect both the installer and the consumer. When measuring concrete moisture, RH testing provides the best way to ensure accurate concrete moisture measurements and a strong, beautiful lifetime for each floor. Be sure to familiarize yourself with ASTM F2170 and choose the best concrete moisture test method for the job.


  1. Patrick Moffett says:

    Jason, when testing lightweight concrete that is a floor fill at 2″ thick, the probe at 20% drilled into the concrete will stick above the surface. Is this acceptable or compromise the test? Thanks for the reply, Patrick

    • Jason Spangler says:

      We have people who use the Rapid RH on shallow pours. The only thing we recommend is that you ensure that there is a good seal between the sensor body and the concrete wall.

  2. Arthur Duffy says:

    When determining the Depth of a probe on an elevated concrete slab on metal deck, the 40% depth is measured to the depth of the thickness of concrete above the “high” flutes or to the thickness of concrete within the “low” flutes. Example: a 3″ deep metal deck with 4.5″ of concrete = a 7.5″ total assembly thickness. Is the probe depth to be 40% of the 4.5″ thickness (1.8″) or of the 7.5″ thickness (thus 3″)?

  3. bob says:

    If i have an area of approx 5000 sq ft and have done the required testing for the area, and 5 fail and 3 pass does the whole area fail? How do you handle this problem?

    • Jason Spangler says:


      At this point, if one test fails, they all fail. I would verify that the hole depths are consistent and that environmental conditions are at service conditions. Good luck.


  4. Enric says:

    how can we deal with very thick concrete pour?

    i have to test an 18 000 sqft area of 10″ thick concrete which has some parts (around 10% of the total area) of the slab as thick as 30 inches, as per ASTM F2170, i would have to drill a 12″ hole in the slab.

    at that depth, using the sensor reader will be quite complicated, how would you proceed with this?

    thank you

    • Jason Spangler says:


      Thanks for the question. When you have time, give me a call at 800-634-9961 X235.



  5. Clinton Burch says:

    I appreciate this means to contact you. I have a 7″ concrete roof deck on metal decking that I need to get tested for moisture/humidity levels. Can you please let me know your recommendation on this?

    • Jason Spangler says:


      Thanks for the question. First, I have to state that F2170 is specified for interior applications that are under consistent ambient air controls. That being said, there are many people that have used F2170 testing methodology for testing roof decks with this understanding. The first thing I would look at is the assembly that you are installing. Does the finish roof product have specifications for testing the concrete deck? If not, call their technical team and ask the questions. Sometimes online and print information isn’t updated expeditiously. Once you find out the methodology they require to meet warranty, I would reach out to someone within RCI in your area to conduct the tests. I hope this helps.


  6. Mike Kemp says:

    I have heard two different opinions on locations of holes.
    Some say you should test within 3′-0″ of slab edge and some say that you should be at least three feet away from slab edge.

    • Jason Spangler says:


      Thanks for the question. Here is what the ASTM F2170 standard (in situ relative humidity testing) actually states:

      10.1.2 Select test locations to provide information about
      moisture distribution across the entire concrete floor slab,
      especially areas of potential high moisture. Include a test
      location within 3 ft (1 m) of each exterior wall.

      So this isn’t really an opinion. I hope this helps.

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