When is Concrete Moisture Testing Most Necessary?

Necessary-concrete-moisture-testingConcrete moisture testing is a necessary step in the process of any construction project, and in many other cases as well, as a concrete slab moisture test is the most cost-effective means of determining:

  • The optimal time frame for installing new flooring
  • The viability of the chosen products for the location
  • The reliability of existing flooring
  • The origin and causes of a flooring failure

A concrete slab moisture test provides different information for different contexts, and is most necessary in these scenarios:

1. Concrete Moisture Testing in New Construction

During a new construction project, the data provided by a concrete slab moisture test is the only reliable information for determining that the flooring products are the right ones for the job, and that the flooring installation will have the highest potential for long term  success.


Concrete moisture testing can be conducted once the building has all of its doors and windows installed and enclosed, the HVAC system is up and running, and the temperature of the building has been maintained at normal use conditions for at least 48 hours. Conducting tests in normal operating conditions will ensure that the moisture will be running through the concrete at the same rate it will be when the building is in operation.

These conditions are not only optimal for concrete slab testing, but are also the requirements per ASTM standards, as tests performed outside of these parameters will provide unreliable data. Obviously, decisions regarding the installation of flooring based on inaccurate or unreliable data can then lead to a floor failure.

  • Testing is necessary before and during flooring installation

During a flooring installation is arguably the most critical time for testing, once the relative quality of the concrete has been established. When workers and materials are brought into a building, additional moisture sources have been introduced to the environment. Building materials (drywall, plaster, etc.), adhesives, and worker respiration can all add considerable amounts of moisture to the immediate environment -- enough to create its own “moisture failure”.

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2. Concrete Slab Moisture Test in Existing Slabs

  • Remodel Projects

A concrete slab moisture test is necessary even months before the scheduled remodel, prior to the final scope of the remodel. This allows the opportunity to factor into the budget the costs and timing for the floor replacement.


When concrete moisture testing is conducted well in advance of the remodel, the information provided by the moisture tests can be translated into recommendations written in a report. When provided this information, anyone bidding on the remodel project will know which products will be necessary and appropriate to include in the bid, leaving much less opportunity for surprises or change orders.

  • Concrete testing in occupied spaces

In the best case remodel scenario for occupied spaces, concrete slab moisture tests can be conducted outside of business  hours, so that normal operations aren’t interrupted. If the building is furnished, the field technicians should conduct tests underneath fixtures or in out-of-the-way places so that the test sites don’t create hazards and aren’t visible to customers. Field technicians should also repair any areas of the flooring where tests were conducted so it’s as if they were never there.


  • Pre-Tenancy Due Diligence Testing

When a building is being considered for purchase or tenancy, concrete moisture testing is the most effective means of determining the current and future status of the building’s flooring. In this case, a field technician can conduct a host of tests, including a sub-slab condition inspection, also known as coring. The purpose of this test is to assess the quality and location of a vapor retarder, which is crucial to the long term success of any on-grade flooring installation. In many cases, however, the quality and location of the vapor retarder is unknown. To make this determination, the field technician will core through the concrete slab and assess the presence, quality, and location of the vapor retarder. This information can be extremely useful in predicting the life of installed flooring.

  • Flooring Failure

When flooring adhesives are applied to a concrete slab and then flooring is placed directly on top of it, water vapor from the concrete moves thru the slab and interacts with the glue. In many cases, the result is that the moisture works to debond the flooring materials, which creates bubbling or peeling in the flooring.


When flooring has failed, it’s important to conduct concrete moisture testing to determine the source of the moisture. What’s even more important though, is that the concrete is tested not only where the flooring is failing, but also (if possible) in a place where it’s still in good shape.

A trained concrete moisture testing professional will gather multiple samples in multiple locations for comparative purposes. In this case, more is always better. And if the building is occupied, the company involved in the concrete moisture testing should ensure that the area is secured so that the testing doesn’t create an additional hazard to the building occupants.


Concrete moisture testing is often necessary, but only effective when the conditions are correct.

In all cases, the environment must be factored in, before and during any and all testing. This information MUST be recorded and photographed to ensure that the site has been accurately monitored and tested, and that the data has been recorded correctly. If the environment is not suitable for testing, then steps to modify the environment, such as removing any environmentally introduced moisture, should be taken. Accurate testing is possible only when the conditions are appropriate; otherwise the data may be more misleading than helpful.


One final note:

While the need to test on-ground concrete slabs is commonly accepted, the need to test elevated slabs is less understood. In a multi-storey building, it’s important to test every concrete slab at every level of the building. The environmental conditions within each level can affect the moisture in the concrete slab.


For more information about the most effective and reliable concrete moisture testing methods, contact an IFTI professional at 800-490-3657, or contact us at info@ifti.com.

IFTI Staff

Written by IFTI Staff