Nothing can ruin your day faster than a callback to a jobsite you thought you were finished with. Callbacks inevitably cost you time, money, reputation and hassle as you determine what the cause of the problem is, who is responsible, and what it will take to correct the problem. At no time is this truer than when the problem is a moisture issue related to the concrete slab. Moisture-related concrete problems can show up in slab strength, performance or appearance, warping or cracked flooring, adhesive failures, mold, finish flaws and more.
Prevention is really your best option but, by definition, prevention happens before a problem could possibly arise, right? Here are three tips to provide that ounce of prevention and save you the trouble of preventable call backs.
1. Understand the specs
Any building project is comprised of a team of professionals working together to establish the architect’s plan and the client’s dream, and sometimes that means understanding not just your own field of expertise, but some basics from the other contractors as well.
How does this come into play when understanding concrete moisture?
Understanding how the myriad of materials will interact with each other is just as important as understanding the dimensions of the structure. For example, if the plans specify a lightweight concrete installation, a savvy flooring installer will verify that the concrete moisture testing has not been specified as calcium chloride testing. Why? According to ASTM, calcium chloride (CaCl) testing is specifically disallowed for lightweight concrete applications. Its accuracy has proven to be very problematic in lightweight concrete applications (as well as in general moisture measurement situations for concrete). We’ll look at why in a minute.
2. Measure the moisture
Moisture in concrete can be particularly insidious because of the process that constitutes drying in the concrete slab. As the water from the initial batch mix moves to the surface, it evaporates and allows more moisture to move to the surface in a continual process until the moisture levels in the slab are roughly equivalent to those in the surrounding air. Just like it takes more time for the cars at the back of a traffic jam to get moving, the moisture levels deeper in the slab will be more concentrated than at the surface and require more time to make their way to the surface. Only accurate concrete moisture testing will be able to accurately tell you what the overall moisture picture is. Contrary to some accepted industry practices, only a test method that tests in the slab will provide accurate moisture readings.
This is why the accuracy of CaCl testing, the hood method, the plastic sheet method or any other surface-based or rule-of-thumb guideline for concrete moisture testing cannot be trusted. They read at the surface of the slab but not deeper into the slab itself. Any moisture source not directly at the slab surface, including high internal moisture levels, groundwater or leaking plumbing, will not register on a surface-based moisture test. If the slab is sealed before that moisture can exit the slab, it may very well bring the entire slab above the moisture tolerance levels of any material it contacts once it equilibrates.
Relative humidity (RH) testing, like the Rapid RH®, tests concrete moisture through the use of sensors placed within the slab itself, at a depth proven to indicate the final moisture level of the slab if it were sealed at that point. The Rapid RH® has the advantage, too, of being the only RH test method to leave its sensors in place in the slab so that they remain equilibrated, allowing instant repeat testing as often as necessary to monitor the drying progress of the concrete, and letting flooring and building professionals adjust their plan, if conditions are impacting the drying schedule based on accurate information.
3. Know your product moisture tolerances
It used to be that flooring products could more successfully tolerate higher-than-tested moisture levels when they occurred, due in part to their primary source from petroleum-based materials. But with the move of the past years towards building materials with lower volatile organic compounds (VOCs), there has also been a corresponding change in the moisture tolerance margins of these products; definitely better for the environment, but less predictable for the industry. While it would be premature to suggest that the new products aren’t better in terms of performance or longevity, the present reality is that these new products have highlighted a knowledge area in the flooring and concrete industry that was simpler to overlook in the past. Accurate moisture measurement has always been critical for any building project’s success, and as new products reach the market, accurate moisture testing is foundational to determining their success. Installers, contractors and even architects and designers must understand the moisture tolerance limitations of the products they will be using.
Manufacturers, too, have realized the importance of knowing their products’ capacity to remain functional in various moisture situations and will provide RH tolerance guidelines for each product. Our RHSpec App puts this information at your fingertips with quick and easy mobile access to over 120 major manufacturers’ relative humidity specifications. However, by knowing both the accurate concrete moisture RH level and the specified product’s moisture tolerance, you can make the correct choice best suited to job site conditions so that you won’t be back later.
Up-to-date, accurate concrete moisture measurement lets each contractor quickly assess schedule realities, and be sure that moisture tolerances of any subsequent building or flooring materials meet the moisture realities of the concrete. Why have to come back to a cupped wood floor or a carpet of mildew when a simple and affordable moisture test can prevent the problem in the first place?
Understanding the specs, accurately testing concrete moisture, and knowing product moisture tolerances are three steps sure to keep your schedule free from those pesky callbacks.