The most common moisture control system failures that I have seen involve subfloor prep and improper application. Most systems require a specific Concrete Surface Profile (CSP) and a porous slab free of any sealers. In order for most systems to work, they must be able to penetrate the concrete. Grinding or shot blasting is often a necessity.
Improper application is self-explanatory. Moisture control systems require a specific application rate. A metering device (trowel or roller) is required to allow the proper amount of product to be applied. These products are carefully tested and failure is, or should be, expected if the application instructions are not followed.
For quasi-solid type moisture systems, the cause for failure to mitigate or block the moisture transfer is improper application (spread rate) over the substrate. These incidences fall under human error. Not paying attention to the wear on the trowel-specific nibs for a 2, 3, or 4-in-1 adhesive product will leave a progressively thinner film until the nibs have worn down to leave a standard notch trowel profile and no moisture protection capability.
Then there is the spread rate application for liquid/epoxy type substrate sealers that may not be adhered to, either from lack of training or attempting to stretch the product beyond its minimum recommended spread rate to save a few dollars. Chemically and physically speaking, the technology in product engineering and the manufacturing process minimize product-related failures. In the rare case that the products do fail, the failure would be systemic and not limited to the one job problem a contractor is experiencing.
Standard felt-asphalt-felt-asphalt systems also fail from human error as will felt-visqueen systems. Not overlapping seams, not taping off seams, pinches, cuts, or pierced materials are all common challenges.
There are many different multifunctional adhesive moisture control systems on the market and they are great if they are applied according to manufacturer’s guidelines. But in many cases, when we see a failure, it is due to the application process, not a system failure. Primarily, it’s the stop and start location of adhesive where the installer has a break in the moisture control system and bond connection to the substrate. This is outlined in the photo above. This will create a weak spot in the adhesive bond, and when placed under stress from moisture, this location will buckle, which is why it’s so important to read manufacturer’s guidelines.