A costly problem

Focus on concrete moisture and mitigation

Though under-slab barriers block the migration of moisture from the ground, there is water in the concrete itself — as part of the mix — and that water vapor often gets trapped causing such problems as bubbling and curling tile as it migrates through the concrete.

Damage to flooring from concrete slab moisture costs U.S. companies upwards of $1 billion each year. When we interviewed flooring industry experts, more than 70% of them reported that they experience moisture issues “often,” with 100% of those surveyed in unanimous agreement that they had experienced some moisture issues.

Moisture issues show up as distorted flooring (such as curling and buckling), adhesive coming through the joints and alkalinity. They can also appear as the white streaks that appear, especially near seams.

Moisture issues have become common due to a number of changes over the past 10 to 15 years, from aggressive building schedules to sustainability trends.

FAST TRACK: Fast-track schedules mean that often the under-slab moisture barrier may be omitted or not installed correctly. And slabs can’t air dry because the slab is not in a conducive environment to dry, which might take an extra 45 to 180 days.

Also, there is moisture in the slab itself, as part of the mix. If the slab is not allowed to adequately dry, that moisture vapor often gets trapped and causes flooring problems as it migrates upward through the slab.

Many of the new mixes contain more water to begin with. A lightweight mix has about 11% more water. And mixes with more fly ash are denser and, therefore, take longer to dry.

Also, many new types of floor coverings are more susceptible to damage because of their composition. Once moisture damages the inner layers, it often causes the flooring to distort. Many new types of flooring become dimensionally unstable in the presence of moisture vapor, and many sound isolation materials absorb moisture and cause problems.

GREEN: Research estimates that more than seven in 10 new-build projects are pursuing LEED (Leadership in Energy & Environmental Design) certification. In doing so, many experience flooring problems. For example, more fly ash creates denser concrete that takes longer to dry, and strict LEED air-quality requirements encourage architects to specify low-VOC adhesives.

These formulas contain water, which therefore makes them more susceptible to re-emulsifying in the presence of alkalis. Older adhesives tolerated moisture better.

TESTING: In every case where moisture-sensitive flooring will be placed over a concrete slab, moisture testing should be performed regardless of age or grade, and all warranties require testing. The most reliable and most widely recognized method is the Relative Humidity (RH) Probe test.

According to ASTM F2170, a probe is inserted into the concrete slab to measure the moisture. After 72 hours, a numerical read ing determines whether mitigation will be necessary.

Many flooring problems show up as damage from alkalinity, and pH testing can prevent them. The soluble salts migrate to the surface of the slab and degrade the water-based adhesive and, in extreme cases, the flooring itself. These problems often show up as oozing adhesive at the joints or seams of the flooring and as unsightly salt deposits on the slab.

MITIGATION: Choosing a mitigation method is an important decision. It’s important to consider not only the cost of materials and labor, but also the cost of downtime. A rolled moisture barrier is both time- and cost-efficient, and it can be installed in one night, so there is no downtime and no days of lost business.

Effective upfront planning is crucial to the process:

  • Include a moisture mitigation contingency for both time and money.
  • Conduct an RH in-situ probe test to determine the need for mitigation, per ASTM protocol.
  • Choose the best mitigation method for the RH level, pH level, budget and schedule parameters.
  • Install flooring with confidence.

On average, every five to seven years, most retail spaces get new flooring. The installation of a new floor can be time consuming and costly. In some cases, stores are closed for days and must take additional time to move fixtures and product out and then replace them. For all these reasons, it’s important to get it right from the start.

Jennifer Chambers is national accounts manager for VersaShield Rolled Moisture Barrier with Halex Corporation. Previously, she worked for IFTI (Independent Floor Testing and Inspection). She is a Certified Moisture Testing Technician.

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