Concrete needs moisture testing every time flooring is changed
Millions, if not billions, of dollars are spent every year to replace, repair and correct floor covering problems related to excessive moisture and elevated pH levels of concrete floor slabs.
Proper moisture testing
Proper testing in advance of installing a new floor or replacing an existing floor is the only way of knowing the moisture condition of the concrete rather than guessing what it might be.
When should you test? Always. Test if it’s old or new concrete, even if the existing flooring material that’s installed looks in good shape. All concrete slabs should be tested for moisture regardless of age or grade level. On-grade, above-grade, below-grade – from the penthouse to the basement – if it’s concrete slab, test it.
1. ASTM F 2170 – Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using In Situ probes, measures moisture inside a concrete slab
2. ASTM F 1869– Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous calcium Chloride, measure vapor emission at the concrete surface
Both testing methods provide valuable information, and it’s good idea to perform both in addition to the pH test. Usually these three tests are done at the same time and the data collected will provide a relevant understanding of the existing concrete slab’s moisture condition.
Who should do the testing
There is much concern about whose responsibility it is to test the floor. The Floor Covering Industry White Paper Position Statement on Moisture Emission Testing recommends independent testing rather than assuming the floor covering installer, the general contractor or landlord/developer will do the right thing and test the floor.
The best way for the owner to assure that the testing gets done is to write a testing specification themselves. A simple statement such as “install floor covering according to manufacturer’s instructions” is not enough. What is needed is to create a specification section regarding moisture testing that will leave no question about what testing is to be done, when the floor will be tested, who is to do the testing, how the results are to be reported and who will receive the copy of the test report.
Elements of specification
The elements of moisture-testing specifications should include:
Type of testing to be done – usually ASTM F 1869 and ASTM F 2170 moisture tests and pH testing per ASTM F 710
Number of tests – the standard calls for three tests for the first 1,000square feet and one test for each 1,000 square feet thereafter, but the owner may change the number of tests based on their needs.
Timing of testing – the temperature and humidity conditions are important and on new construction, testing should be done after the building is enclosed and the HVAC system is up and running. For a renovation project, the testing should be done at least a month prior to the scheduled floor covering installation, so there is adequate time for corrective measures to be taken if they are necessary.
Reporting – test reports should contain as much information as possible about the conditions at the time of testing, methodology of testing and test results. This is an important way to document not only the test results but the accuracy of the testing that was done. The specification should also identify who is to receive the report – the owner, general contractor, architect or all parties.
Mapping – the more sophisticated reporting done by some independent agencies will show the test results on a map of the facility, which can help the construction team identify problem areas in the floor.
Repair options – the report should include options for repairing a floor that exceeds the manufacturer’s limits.
The moisture testing specification may be standalone specification as part of a concrete floor slab section that details some of the key points of a concrete industry standard designed to prevent floor covering moisture problems. The details may include the need for the concrete to be dry, clean, smooth, and free of contamination, the inclusion of a proper water-cement ratio, the installation of a vapor retarder directly under slabs on or below grade, the use of moisture-retaining coverings for curing concrete and so on.
Concrete floor moisture-related failures continue to cost property owners a great of money and lost time. It pays for these parties to take charge of the process, requiring testing by independent agencies and creating detailed specifications that direct the entire construction team as to what is expected of them so potential flooring problems can be identified and solved in advance.
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