Don’t Be All Wet
Learn the Secrets to Avoiding Floor Failure – Insist on Moisture Testing
By Terry Nali, Coordinator, INSTALL Twin Cities and a CSI/MSP Member
A common phrase in the commercial flooring industry is: The most beautiful flooring in the world is useless if not installed properly. In this article, I’d like to explore a new motto: A properly installed floor will probably fail if excessive moisture is present in the substrate.
The majority of flooring failures occur because of elevated moisture and/or
alkalinity levels in the substrate. Adhesive bonds break, underlayments rot, flooring warps and mold and bacteria spreads. Moisture intrusion and pH imbalances occur through external and internal third-party sources, because of the improper preparation of floor’s surface, or from improper (or non-use) of moisture and alkalinity testing. And don’t be fooled, excessive moisture issues are not exclusive to on-grade or below-grade floors. Floors have failed on above-grade floors because the cement slab was not given enough time to dry.
Moisture and alkalinity are inherent to concrete and neither can be fully eliminated, but understanding the amount of moisture and alkalinity can help you plan for its movement through the substrate. The American Society for Testing and Materials (ASTM) E 1907 presents: Standard Practices for Determining Moisture-Related Acceptability of Concrete Floors to Receive Moisture Sensitive Finishes. ASTM puts forth eight tests used in the construction industry to determine if unacceptable moisture is present in, or emitting from, concrete slabs.
Flooring manufacturers, too, have standards for acceptable moisture content of the substrate that will host its product. Manufacturers also recommend the preferred method of moisture testing. The majority endorse the
Quantitative Anhydrous Calciu
m Chloride Test, which also is typically the accepted testing method when litigation is involved. Com
mon pH testing employs manual strip tests or digital devices.
Because moisture distribution changes, moisture emission rates also change, and may increase to a level high enough to cause a flooring failure. This can be addressed by measuring moisture with the relative humidity probes, or alternative testing techniques, placed at varying depths throughout the slab. This provides an accurate moisture profile of the concrete substrate. Therefore, testing is done to determine the current condition of the concrete. No test can reveal what the condition of the concrete will be long term. Many uncontrollable factors influence the slab. The instability of these factors compounds the necessity to create as optimal an installation condition as possible.
Drying Time
A common rule for drying time is one month for each inch of slab thickness. However, recent studies show that regardless of the thickness, water vapor emissions decreased at about the same rate. Therefore, current thought is that reducing slab thickness does not significantly reduce drying times.
When drying time is critical, the slab should be p
rotected from external moisture sources. Studies show that re-wetted mature concrete dries much slower than newly poured concrete. For example, adding water to the surface after the 46 day of the drying period increased the emission to 15 lbs, and 5 additional weeks of drying time were required to return to industry-accepted rate of 3 lbs.
Lightweight concrete with a water to cement ratio of 40 percent takes 183 days to reach an emission rate of 3 lbs per 1000 sq. ft. per 24 hours. Although lightweight concrete has its benefits, there is a significantly longer drying time associated with its use. Even finishing techniques can affect drying times. There is evidence to suggest that a power trowel finish dries more slowly than a normal trowel, or float finish. The surface is compacted and densified, making it more difficult for water to evaporate.
Avoiding Misery Underfoot
There are five main ingredients to ensuring a successful floor installation:
- Use manufacturer-recognized moisture testing methods
- Insist that floor prep testing is always done and that protocol is followed precisely
- Insist on a vapor-retarder that is puncture-resistant
- Rectify imprope
r conditions before proceeding with installation
- Be sure that the flooring contractor is competent and well-versed in identifying and understanding improper flooring conditions before installation occurs.
All of these points can be covered if you specify that your contractor has the training, skills and experience to make the right decision, so that the floor does not fail. One way to ensure that is through detailed specification. Mandate that your flooring is installed by a trained, certified professional with at least four years of experience for every installer. That specification still keeps your project open to dozens of prospective, qualified contractors, while at the same time weeding out poorly trained, ill-qualified, less reputable or less-equipped outfits.
About the Author
Terry Nali is coordinator of the Minneapolis-St. Paul-based flooring installation group, INSTALL Twin Cities, which partners with 50 mills and manufacturers in the flooring industry. INSTALL supplies the local construction industry with flooring contractors who use INSTALL-trained professionals exclusively. Nali also works with construction specifiers on specification language that outlines the skills a flo
oring installer must have to be accepted on the job site. To learn more about flooring installation specification, contact Terry at 651-636-0091 or tnali@mncarpenter.org
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