Concrete Moisture Mitigation - June 2012

By Rick Kercheval


Consider this typical and all too frequent scenario. A local high school installs new flooring in its existing gym. Less than two years later, the new gym floors are starting to blister. The building contractor and design architect are called in to assess the problem, and soon all eyes turn to the flooring contractor. The manufacturer of the finished surface is contacted and joins in the analysis discussion. Questions begin to surface. Who performed the testing prior to floor placement? Where are the reports? Is this isolated or do we have a bigger problem that will extend over other areas? What assurance do we have that the problem can be fixed? And who is liable for fixing it?

When situations like this arise, all parties share the burden of accountability—including the architect, contractor and building owner—but the flooring contractor is expected to be the expert. The flooring contractor is expected to be familiar, not only with all types of environments, but also with the best types of flooring finishes to use in each environment according to their manufacturers’ specifications. For these reasons, it is imperative that the flooring contractor know how to complete and analyze the testing properly, because this has implications for the project as well as for the reputation and livelihood of the contractor’s business.

The fact is, in today’s high-cost, low-margin construction economy, it is simply not enough that flooring contractors be knowledgeable in product makeup, green flooring, evolution of adhesives, construction scheduling and efficient project management. Without carefully choosing a flooring contractor that knows about pre-installation and concrete moisture mitigation techniques, the general contractor and building owner can easily find themselves in the same situation as the high school above. And the flooring contractor can incur costly mitigation expense and potential legal liability costs.

The activities performed during a pre-installation investigation are the very essence of the success or demise of a good project. It is critical that the flooring contractor conduct a thorough risk assessment before placing any finish products on the concrete surface. After all, with failures requiring warranty activity generally a very small percentage of any company’s budget, failure to do adequate work on the front end of an installation can produce catastrophic costs for the flooring contractor without a backup blanketed insurance. Avoiding preventable problems is just as important as providing a quality installation.

At the high school, as it turns out, testing was in fact performed, but it was flawed.  The testing analysis looked suspicious and getting the records took some time. Upon reviewing the records, it was evident that the test report showed deficiencies in a few respects. 

First, no climate control factors were recorded during the testing. This means that the testing could have been performed in almost any environment. This is significant when the calcium chloride dome test is the primary source for information, because the testing has to be performed in the conditions under which the floor will exist or at 70º Fahrenheit at 50% relative humidity, plus or minus 3º or 3% humidity. Second, the number of tests applied was fewer than the specified direction defined by the ASTM F1869. Only six tests were applied to a 12,000 square foot gym surface; according to ASTM standards, 15 should have been conducted, three per project plus one for every 1,000 square feet of flooring surface. Further, a glance at the pH testing results yielded acid concrete, which will destroy flooring adhesives. A “healthy” reading is eight to nine; however, on this project, the reading was recorded as five and seven, which is virtually unheard of. This should have set off alarm bells for all involved. Interestingly, the manufacturer of the finished floor had a representative on site for the installation and approved the testing results.

Unfortunately, the construction industry has a generally prescribed protocol of “last one in is the first one to be held accountable” for commercial projects. If flooring finish issues surface, the flooring installation company is the first to be held accountable. What does that mean for flooring contractors? Either they discover preventable issues before failing finishes are a part of that equation, or they pay for the finishes in place a second time with enormous piecemeal and non-disruptive repair times to the owner of the building. 

Simply put, a failed floor finish is a substantial financial cost—usually significantly more than the original investment; a serious impact to business relationships with the prime contractor, architect and especially the owner; and a negative hit to the company’s reputation and brand status, if it is determined that the problem would have been preventable.

After the high school gym tests were revealed, a third-party engineering consultant was hired to test the floor and assess the problem with the existing floor showing present stress. Once again, everyone on the project had a stake in the outcome. What did the tests reveal? 

After the re-testing was complete, it was determined that the engineering firm, in the interest of not damaging the floor finish while school sports activities were underway, had used fewer calcium chloride testing stations on the floor than specified in the testing protocol. In addition, the placement of the tests was completely invalidated because the engineering firm field team forgot the preparation tool to clear off residual mastic adhesive and proceeded to lay the test kits on top of the mastic and not the concrete slab anyway. When this was pointed out, they admitted that they had done wrong and agreed that the testing might be skewed. 

All of these things are enormously critical to assessing a pre-existing potential for failure or a post-failure analysis. It is altogether crushing to watch a quality hard surface or wood floor system come under stress or failure from some abnormal or threatening attribute within the substrate unrelated to the activity of the installation team. 

The high school gym project reflects a laid-back and careless testing acumen combined with a naive subjective conclusion by both the floor manufacturing representative—who was present to view and accept the testing pre-installation but then took a different posture, saying that the testing results were too high, after the flooring failed—and the installation team. That laziness resulted in costly consequences. Testing should not be considered as simply another project function; rather, it should be a serious analysis or discovery of a risky or impossible environment in which to place a finish. It is only when the floor finish becomes threatened or fails outright that the testing history of the floor comes under much greater scrutiny. 

What other sources contributed to the consequences? The design team omitted the vapor barrier material at the last minute to reduce the overall cost to the owner. While that was not the sole reason for the problem, it certainly contributed to the result.

In this case, the subcontractor made the ultimate error by not diligently testing the floor to the letter. If it had, the testing would have shown that something was askew. This would have precipitated a question about the building platform and the subsequent revelation that no vapor barrier was in place. The general contractor was also at fault and should have had some knowledge about the guidelines for the testing and made sure that it was conducted under the normal guidelines of the ASTM protocol. This would include the number of tests required, building environment requirements for testing, and floor finish manufacturers’ maximum sensitivity values of the test results to uncover a potential problem. The bottom line is that everyone needs to be involved in the testing and analysis because, in the end, everyone has a part in proper construction acumen, and this small amount of testing will help determine the risk of applying finishes.

A mitigation system is a system applied to a properly prepared substrate that is designed to mitigate moisture emission issues, including pH, moisture vapor, and air movement through the slab, so that any and all finish surfaces may be applied with the full expectation that the wearing life of the finish will be achieved.

In the event that the testing indicates the substrate needs to be mitigated, there are two considerations for mitigation, chemical mitigation and mechanical mitigation. The former depends upon the age and compound makeup of the concrete matrix, and the latter depends only upon surface compatibility and penetration.

At a different project at a light manufacturing building, the mitigating product was ordered and installed, only to fail after six months. When the sealer manufacturer made the trip to investigate the claim of a warranty due to the failed material, he was informed of a second building failing as well. When the square footage was totaled, it became obvious that the installation team overextended the material by 200% of the square footage to cover both surfaces. Since the order was shipped directly to the project site, the manufacturer knew what the coverage estimates would be, and it was easily calculated that the sealer had no real chance to be successful due to the material extension over twice the advisable project size. This process of mitigation repair is much like hiring a smoker to run a firework stand. In this case, the installation team was unscrupulous and totally responsible. Just checking and testing the slab may resolve half the issue, but the other half is based on the competence of those doing the installation. Most companies get only one chance to bill and collect for a project, or they start all over again at their own expense repairing it if they manage to stay in business at all.

The three important aspects of a successful mitigation still remain the preparation of the substrate, the mitigating system, and the installation team responsible for applying the system. Downplay any one of them and the risks for failure are significantly more likely, even with a remarkably potent product.

Ray Reed of CTC-Geotek Inc. describes a thorough surface preparation like this: “A clean concrete surface is free of form release agents, curing compounds, surface hardeners, oils, grease, food, chemicals, or other contaminants. Previously applied coatings or toppings may need to be removed. Dust, including new dust generated by surface shot blasting or scarifying, must be removed too.” 

The installation team must be trusted by the manufacturer of the mitigating system for successful placement of the product and must have a track record of successful repairs available for review. They must also be competent in explaining how the material and installation scientifically and physically will resolve the issue by addressing the cause and effect of moisture vapor emission.

Most successful systems are from the family of mechanically applied systems. In all cases, it is important that the track record of the material and the installation team not only have an impressive array of significant references but also a good financial standing.  

Discovery of a potential problem on the front end of a project has become the expected norm from all parties involved, including the floor finish subcontractor. Is it fair that the flooring contractor bears the brunt of the burden for mitigation? That is up for debate, but the fact is, the flooring contractor is expected to know that hostile conditions not readily visible may exist and therefore make sound objective analysis before proceeding with a floor finish. 

When discovering a potential problem, it’s important that the flooring contractor document the problem in writing, including identifying the problem; the type of objective, dynamic testing undertaken; and a potential solution if the problem involves concrete moisture content or vapor drive outside the acceptably safe limits prescribed by the manufacturers of the finishes. This information will be available long after the project is completed and the problem is discovered. Documentation is well worth the effort and is an important part of the professional reputation of any flooring contractor who desires to stay in business long term.

In addition, it is important that adhesive manufacturers have correct testing data by which to make their judgments, especially on projects that use an adhesive not endorsed by the flooring manufacturer, since any problem with adhesive will reflect poorly on their product. This is especially true of third party “problem solving” adhesives. These new adhesives must multi-task by suitably neutralizing moisture vapor threats while also maintaining expected bonding integrity of virtually all composition flooring finishes from various manufacturers. Correcting a known moisture problem during the construction phase eliminates a wide variety of potentially catastrophic problems. Potential “costs” can include lost business relationships, poor reference sources and reputation, legal liabilities, and bond and insurance cost surges. 

In the case of the gym, the estimated costs to correct the problems will be significant—possibly in excess of $120,000. These include demolition of a two-year-old sheet vinyl wood grain appearance floor; removal of all adhesives and patching/float materials; surface blasting of concrete for complete decontamination; application of mitigating sealer at least in two coats for most systems; application of a self-leveling underlayment cement to remove surface profile issues; application of float for transition touch-up, adhesives and re-application of original floor finish; provision for all incidental waste containers and refuse removal; and provision for all electrical needs. 

Even though the costs to remediate the 12,000 square foot gym can be in excess of $120,000, not all of the burden is placed with the guilty parties. The owners will have to participate in the mitigating system, since this was a pre-existing condition at the time of installation and would have added cost to the initial installation had it been discovered at that time. While the owners may end up footing half of the bill and reducing the impact to the construction team, the construction parties involved also are losing out on potential revenue from other projects while they replace the failing floor.

The key takeaway for flooring contractors is to either plan for the problem with a proper regimen of scheduled testing and possible correction during the construction, or fix the problem when it is discovered. The key takeaway for the project team—including the architect, contractor and owner—is to put in a contingency to deal with the problem. It is far better to plan for the unexpected than not to have the reserves to correct a potential problem. Most trouble occurs when a potential problem is avoided, ignored or, in the case of the high school, not considered important enough to be properly diagnosed with good testing procedures. Use every possible means to be certain that the concrete has been thoroughly assessed before proceeding. As flooring contractors, we are expected to be the experts. Tens of thousands of dollars are riding on our decisions, and those decisions need to be based upon accurate and quantitative information. The more information that is collected and properly analyzed, the more likely it is that an apparent issue will come into focus. Make certain that the moisture vapor emission condition of the project is not viewed as someone else’s problem. It might be yours.


Copyright 2012 Floor Focus