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Today’s floorcoverings and adhesives have specific requirements for concrete vapor emissions. Installing products outside these levels will void your warranty, cause adhesive failures, promote mold and mildew growth or in time result in the product delaminating, curling or bubbling. Therefore, it is a requirement to test the moisture emissions of your slab prior to installation. This is your protection to insure all manufacturers’ warranties are in force and the product specifications are met.
Concrete Slab Readiness
How do you know your concrete slab is ready to receive floor covering? Currently the universally recognized test for moisture emissions is the calcium chloride ASTM 1869 test method. This test measures the quantity of vapor emitted in pounds of moisture over a 1000 square foot area during 24 hours. The ASTM test, which takes 64 - 72 hours to perform, requires the environment to be acclimatized for 48 hours prior to, and for the entire duration of the test.
In addition to testing for moisture, the surface of the concrete must also be pH tested for alkaline salts which can also cause adhesive failures. Moisture vapor carries alkaline salts to the concrete surface which lead to most adhesive failures.
 Spectra strongly recommends that because of the seriousness, potential cost impact and liability of moisture and pH test results, moisture testing should be performed by a qualified independent agency. This is also the position adopted by the World Floor Covering Association. The owner or general contractor should submit to Spectra a written report on the vapor emission levels and surface alkalinity.
Moisture Transmission
How does moisture transmission occur? One way is cellular migration which can be caused by inadequate outside drain off. The moisture travels from outside into the slab, through the concrete capillaries, and migrates up through the floor systems inside. Another way is hydrostatic pressure from ground water. The majority of moisture problems we encounter are due to controllable construction practices. Frequently in new construction, high moisture is directly related to the amount of water used when mixing the concrete (the water cement ratio), the curing method or the lack of time to allow the moisture to escape once it has been poured, formed, and finished. Under normal conditions, the required time for concrete to dry is 30 days per inch of pour, or 90 to 120 days. Even pan poured upper level floors can create moisture problems if sufficient curing time has not been allowed. Rain or rewetting of the slab before the building is enclosed is a major source of moisture and can extend the drying time significantly. A high quality vapor barrier is essential.
Moisture Remediation
What are the alternatives if the moisture or pH test results are higher than the manufacturer specification? The installation should be postponed until an acceptable test result can be achieved. Desiccant dehumidification may be brought in to accelerate the drying process. Contact Munters Corporation at 1-800-MUNTERS for assistance.
Many surface applied remedies are available and the right one may depend on the source of the moisture, the rate of the moisture vapor transmission and the finished floor covering being installed. If a moisture remedy is utilized the applicator must insure it is compatible with the specified floor covering.
It is Spectra’s recommendation to apply Koester VAP 2000. We have intensively studied this problem and evaluated the chemistry and performance of many alternatives. Spectra will install the Koester system and warrant all products and workmanship. http://www.koesterusa.com/index_vap2000.php
If another moisture remedy product is specified, Spectra will contract to apply the limiter system. In this event Spectra will warrant that the remedy product has been applied correctly. All other installation warranties will be with the manufacturer of the moisture remedy product.
After application of a moisture retarder, additional calcium chloride tests should be performed and results provided to verify the floor meets the manufacturer’s specified moisture emissions rating. When moisture tests are lower than the manufacturer’s tolerance, a successful installation will proceed.
Preventing Moisture
How can we prevent these problems? You may never be able to completely prevent moisture problems but you can minimize them. Remember the big five steps in controlling moisture.
- Install a quality, uncompromised vapor barrier over the crushed fill
- Use as low a water/cement ratio as possible
- Mechanically remove curing compounds as quickly as possible after the concrete has set
- Avoid rewetting of the slab
- Climatize the construction environment as soon as possible after placement of concrete
At Spectra we appreciate your cooperation and efforts to responsibly consider moisture in concrete as it will affect your floor coverings for years to come.
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