Moisture Prevention and the Effect on Tile Installations

By Arthur Mintie, LATICRETE Sr. Director, Technical Services

The need for moisture protection and waterproofing has become more significant over the years as savvy construction professionals continue to recognize the long-term benefits offered by relatively inexpensive prevention mechanisms, namely moisture vapor emission control products. Without proper protection, moisture can migrate through the substrate and setting system and adversely affect moisture-sensitive installation materials and finishes, causing the overall installation to be at risk for failure and costly repairs.

Illustration of how moisture moves through a concrete slab, breaks down the adhesive and damages finished flooring.
Illustration of how moisture moves through a concrete slab, breaks down the adhesive and damages finished flooring. | Illustration courtesy Laticrete International

Types of Moisture

The most serious of the two types of moisture can move through a concrete slab and impact tile and flooring installations is negative hydrostatic pressure — water that meets the bottom of a concrete slab.

Negative hydrostatic pressure can be alleviated by the placement of good vapor retarder sheets below the concrete slab, the use of sump pumps, foundation drainage or good landscaping practices, prior to the installation of flooring materials. After the fact, it is challenging to address and correct these issues. Any remediation efforts are more than likely beyond the capabilities of the flooring installer, so experts in water intrusion remediation should be consulted.

The second and most common type of moisture found is moisture vapor emissions (MVE). MVE that transpire through concrete slabs are fine if they are at levels in which the finish flooring and installation materials can tolerate. Typically, MVE will normalize over time in most installations, and flooring installations can then take place. It is important for installers to note that ceramic tile installations are more inherently resistant to the effects of MVE and are good solutions for applications where these conditions may persist.

Additionally, installers need to follow the manufacturer’s instructions to identify the limits of MVE with floor finishes and installation materials. If the MVE rate exceeds what is recommended, appropriate moisture vapor mitigation systems can be employed. Most of these products are two-component epoxy resin based and create a barrier on the concrete surface to prevent MVE from reaching the installation and finish flooring materials.

Moisture Environments

Aside from water present in the concrete slab, tile installations can be impacted by the installation’s environment. For example, in Tampa, FL, the average yearly relative humidity is 74%. During the summer months, Tampa averages a relative humidity between 87% and 91% in the morning, making it one of the most humid cities in the nation. The effects of moisture vapor transmission, humidity, temperature and dew point can affect certain moisture-sensitive finishes.

To set ceramic tile in a damp environment, products must be able to accommodate damp weather conditions and not contribute to mold or mildew. High-performance latex thinset mortars are generally well-suited for these environments due to their composition and characteristics.

Other factors that may influence the installation of tile can include the pH of the concrete or the presence of curing compounds/sealers on the concrete.

Cementitious Waterproofing Membrane, a single-component, polymer-fortified cement-based waterproofing material is designed to perform under both negative and positive hydrostatic pressure up to two bars (29 pounds per square inch).
Cementitious Waterproofing Membrane, a single-component, polymer-fortified cement-based waterproofing material is designed to perform under both negative and positive hydrostatic pressure up to two bars (29 lbs./per square inch). | Photo courtesy Laticrete International

Testing for Moisture/Effects of Moisture on Tile and Flooring

With an increase in moisture-sensitive flooring materials such as luxury vinyl tile, vinyl composition tile and carpet tiles, it is imperative to address any moisture concerns early on in the construction process. Addressing moisture vapor emissions should be a key component of proper surface preparation across the entire industry, and if not addressed, could result in additional costs and repair time for flooring installation failures in the long run.

To determine exactly how much moisture is present on a jobsite and decide on the best tile and flooring installation materials, there are various approaches and testing methods that can be used to assess moisture conditions; such as using relative humidity meters in accordance with ASTM F2170. Although testing is essential, the results are purely a snapshot in time as to what the current situation looks like and cannot guarantee moisture will not become a problem in the future.

Conclusion

While not new, concern over moisture mitigation has grown significantly as condensed construction timelines increase in frequency. This often means less time is allotted for concrete slabs to properly dry, which can result in unsuitable relative humidity levels for flooring installations to perform. A moisture vapor barrier product is highly advised for use before placing underlayments or finished flooring in these conditions.

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