Understanding ASTM F-2170 and Its Critical Role in Concrete Moisture Testing

There are some things that just need to be done a certain way. When it comes to assessing

moisture in concrete, whether in large-scale commercial construction or a residential basement, one method stands out as the gold standard: ASTM F-2170.

Though its title may not be immediately revealing, ASTM F-2170 is recognized as the

benchmark for accurate moisture measurement in concrete. But what does it mean, and why is it the preferred standard?

In this article, we'll explore:

• How to properly conduct concrete moisture tests to ASTM standards

• The most crucial applications for ASTM F-2170-compliant testing

• Why this standard surpasses previous moisture testing methods

Breaking Down ASTM F-2170

The methodology of testing relative humidity (RH) in concrete using ASTM F-2170 was originally practiced in Europe before being introduced to the U.S. in 1999 and officially published as a standard in 2001. The need for a more accurate and reliable concrete moisture measurement method arose due to frequent floor failures, leading to the development of ASTM F-2170.

Limitations of Previous Moisture Testing Methods

Before ASTM F-2170, various moisture testing methods were used, but they often lacked

accuracy and consistency. One of the most widely used methods was the calcium chloride test. This test involved placing anhydrous calcium chloride crystals on the concrete surface and weighing them after 72 hours to determine how much moisture they had absorbed. The

problem? The results could be skewed by external environmental conditions, such as changes in humidity or rain, leading to misleading conclusions and potential flooring failures.

How the In-Situ Method Transformed Moisture Testing

Unlike surface-based moisture tests, ASTM F-2170 employs an in situ testing method, which

measures moisture levels within the concrete slab rather than just on the surface. This is done by inserting hygrometer probes into sealed holes within the slab, providing a more reliable reading of the concrete’s internal moisture levels.

Key Benefits of ASTM F-2170 Testing

1. More Accurate Results: Since probes are placed inside the concrete slab, the

readings are not influenced by external humidity fluctuations.

2. Identifies Hidden Moisture: Surface tests often miss underlying moisture issues,

which can lead to unexpected flooring failures.

3. More Reliable than Moisture Meters: Pin-type moisture meters rely on electrical

conductivity and only provide surface-level readings, while pinless meters can’t measure

deeper than ¾ inch. ASTM F-2170 ensures moisture readings are taken at a depth that

accurately reflects the slab’s overall condition.

4. Time Efficiency: The in situ method provides reliable readings within 24 hours,

compared to the lengthy calcium chloride test.

5. Standardized Testing: ASTM F-2170 specifies the number of test probes required per

1,000 square feet, ensuring consistency in measurement.

Step-by-Step Guide to ASTM F-2170 Concrete Humidity Testing

Properly administering an ASTM F-2170-compliant test involves seven key steps:

1. Identify Areas of Concern: Use a pinless moisture meter to locate high-risk areas.

2. Drill Test Holes: Drill three holes for the first 1,000 square feet of concrete to a depth

of 40% of the slab’s thickness (or 20% for slabs drying from both sides). Drill additional

holes as required for larger areas.

3. Clean the Holes: Remove debris with a wire brush and vacuum.

4. Inspect the Holes: Ensure they are free of coarse aggregate obstructions.

5. Insert Probe Sleeves: Place them at the correct depth.

6. Seal and Wait: Insert the probes, cap the openings, and wait 24 hours for the readings

to equilibrate.

7. Take Measurements: Use a hygrometer to record relative humidity levels.

Selecting the Right Hygrometer Probes: Reusable vs.

Disposable

Both reusable and disposable probes are available for ASTM F-2170 testing. While disposable

probes are convenient, reusable probes offer two significant advantages:

• Cost Efficiency – Reusable probes can be used multiple times, reducing long-term

  expenses.

• Higher Accuracy – Reusable probes generally use more advanced sensor technology,

  leading to more reliable readings.

The Most Crucial Applications for ASTM F-2170 Testing

Moisture testing is always valuable, but it is particularly critical before installing flooring over a concrete slab. Flooring failures due to excess moisture are costly and disruptive. For example, large commercial retailers with tile flooring installed over concrete must ensure the slab is properly tested. Without accurate moisture measurement, tile can tent or delaminate, leading to expensive repairs and potential store closures.

Why ASTM F-2170 Matters for Long-Term Flooring

Success

The ASTM F-2170 standard was developed to prevent flooring failures caused by excessive

moisture in concrete. The American Society for Testing and Materials (ASTM) explicitly

acknowledges that improper moisture levels can cause delamination, peeling, staining, and

microbial growth under floor coverings. Ensuring concrete has reached equilibrium moisture

content before installing flooring is essential for long-term durability.

Environmental Factors Impacting Concrete Moisture

Several factors can impact concrete moisture levels:

• Ambient Humidity – Concrete absorbs and releases moisture based on surrounding

  humidity levels, affecting surface test accuracy.

• Ground Moisture – Vapor from below the slab can permeate into the concrete, making

  vapor barriers and proper drainage essential.

• Drying Conditions – Concrete must be allowed sufficient time to dry before flooring

  installation.

Final Thoughts

Concrete moisture testing has come a long way, and ASTM F-2170 has revolutionized the

industry by providing a standardized, accurate method for assessing moisture levels. By

adopting in situ relative humidity testing, contractors and flooring professionals can avoid costly failures and ensure the longevity of their installations. As technology advances, ASTM-

compliant moisture measurement systems will continue to improve, further enhancing accuracy and reliability in the field of concrete moisture management.

Hire C+C Inspection Services for Reliable ASTM F-2170 Testing

When it comes to ensuring accurate and ASTM-compliant concrete moisture testing, trust C+C Inspection Services. Our certified Relative Humidity Testing Technicians provide precise, reliable, and efficient testing to help you avoid costly flooring failures. Contact us today to schedule an assessment and ensure your concrete slabs meet the highest industry standards.