Most liquid applied products utilize a fabric and liquid. While the fabric does add some reinforcement properties, more importantly, it assures that when the second coat is applied the proper film thickness will be achieved to provide lasting crack protection.


Some products utilize an adhesive application for bonding. Always make sure the concrete falls within the proper Moisture Vapor Level or Relative Humidity and pH levels. Trapping moisture under a membrane or having a high pH can be very detrimental to adhesive-applied products.

My fairly recent entry into an inspection and consulting career has already broadened my horizons considerably. In my previous position I had the good fortune of landing a job developing a national training program after working nearly three decades in the field installing. During the course of that endeavor, the closeness of my relationships with manufacturers in learning about their products, coupled with numerous visits (as part of our training programs) to the Tile Council of North America Performance Testing Lab, allowed me to develop an unusually candid knowledge of how things really worked and pass that knowledge to others. Then there were the phone calls, literally thousands of them, looking for answers about either what went wrong or how to avoid problems. If you did not have the answer, you had to find the answer, all part of the job. After ten years of that environment, you tend to get the feeling you’re on top of things. One thing is certain in life:  as soon as you think you know something, somebody or something will come along and show you that you don’t know as much as you think you know. Such has been the experience for me since embarking on my twilight career of inspection and consulting.



Even the best membranes will not provide crack protection unless the tile is properly supported by thinset mortar. Coverage is very critical when installing over a compressible surface.

In my semi retirement, I find myself in a new city, sometimes two, nearly every week. Inevitably, by virtue of the fact I am there, something has gone wrong with a tile or stone installation. Nearly as inevitable, as part of the job some removal will be required to discover why things went wrong. Occasionally, testing will have to be done to assure the products involved met standards.  Of course we already know that, 75 to 80% of the time, it surely is a manufacturing or product issue according to all involved except the manufacturer. Just as obvious, 97.5% of the time, as testing will demonstrate, there is no product issue. Just a footnote here before proceeding further: I used to use a figure of 98.5% relative to the unlikely fact that it could truly be a product issue. This year, after slightly more than 100 job reviews, two actually did have product issues so I am now lowering my expectations by a full percentage point to err on the side of caution. That’s a joke for those that don’t get it. While possible, it is not probable the product is the issue.

With that, let’s start on product and performance expectations for crack suppression membranes. To allow for addressing the meatier issues in some depth we should start with the simple statement “if it sounds too good to be true, it is.” That saves me a lot of typing and the magazine valuable space in explaining the obvious. Membranes are not supporting structures nor will allowing for a half inch of movement be either a true statement or of any value to you in the installation. In selecting the right products, you need to make a realistic assessment of the intended use of the floor and include consideration of the maintenance chemicals and procedures. An elevator lobby for a condominium project has very different performance needs from the powder room in the penthouse suite. Likewise a shopping mall is much different than the dentist office vestibule. It is entirely possible that one product could be used in both applications, however, I would stop short of saying it’s likely.

Crack suppression membranes are often highly deformable can offer great elasticity and the ability to resist great amounts of movement. These same features may also mean it has a relatively low resistance to compression such as a fully loaded hand truck or in some not so unusual instances for commercial applications, a pallet jack or scissors lift to change the light bulbs. The type of substrate should also be included as a consideration. Is it dry concrete or does the slab have possibly poor site drainage or other problems such as an excessive water ratio in the mix, causing high vapor emission? It may be lightweight gypsum and a sealer needs to be applied. In wood structures, plywood over a finished basement may be very different than OSB over a crawl space. A membrane used on OSB over a crawl space can be as nearly problematic as an installation over damp concrete in areas of high moisture or rainfall when the crawl space is not properly ventilated. You should always know the use of the floor and limitations of the product prior to the installation. Some of this may sound to a few like it is not in the realm of the installer’s responsibility. If you are the knowledgeable flooring professional who was hired to do the job, it is your responsibility to know the benefits and limitations of your trade products.



This marble was installed over a control joint without placing a movement accommodation joint at the closest grout joint per manufacturer instructions and industry recommendations. The result is 72 feet of cracked stone that now needs replacement.

Another consideration is what size and type of material is to be installed over the membrane. I bristle a little when somebody categorically says our product is fine for tile and stone. As we know there are many types of tile. However, there is only one type of tile used for testing the elastic abilities of a membrane, and that is quarry tile. Ceramic floor tile and porcelain tile typically have a fair amount of elasticity relatively speaking. Half-inch quarry tile has an even greater tolerance of movement. The testing under tile industry standards for the crack bridging abilities of any membrane product utilizes quarry tile.  We all know that with most stone products, we lose a certain percentage just in getting them cut and installed on the floor. Stone is very intolerant of any movement without an accompanying fracture. Every vein in stone is a crack waiting to happen. If your project is of any size and involves the installation of thin stone flooring over a membrane, it would be very prudent to ask if the manufacturer has any crack suppression data related to the particular type of stone you are using. While not a frequent occurrence, it is not at all that unusual for a membrane to be both too compressive and thin stone flooring too inflexible for use over certain types of membranes, especially in commercial applications.

Membrane placement in the flooring sandwich is another consideration. In the testing process, a thin layer of setting material in 1/8” thickness with 100% coverage is used in establishing the performance values of the membrane product. Yet often we see a bonded crack suppression membrane under a mortar bed or ¾” or more of medium bed mortar. The crack suppression abilities of a membrane are very limited when placed anywhere other than immediately under the tile. The further away from the tile interface the less likely they are to provide you with the crack suppression abilities you seek. To get the best performance out of a membrane system they need to be located as close to the tile surface as possible. Any prep work such as floor fill or correcting out-of-level conditions should occur prior to the placement of the membrane.

Without exception, the one item most often consistently missing in membrane installations is the lack of any movement joints or failure to carry control joints through to the next closest grout joint. Crack suppression membranes do not eliminate the need for movement accommodation joints. On the contrary, if membranes are to perform their task, they need a place to move to. Control joints are designed to control where cracking will occur. That the joints will crack at some point in time is relatively certain. In the case of random slab cracks, the energy of the cracking is stored in the membrane for transit to a predetermined location. That location would be the movement accommodation joints in the field and/or expansion joints at the perimeter of the installation. For floors with lengths greater than 25’ total, movement joints need to be placed in the field of installation. In such installations perimeter joints alone will not provide the necessary movement accommodation. Crack suppression membranes, by design, dissipate energy; they store it for transit just like a truck hauling a load.  Once the energy of the movement arrives at its destination, the movement accommodation joint, it unloads and is ready for another trip. No joint, no stress removal, and cracked grout or loose tiles are not out of the realm of possibilities.

The above is a brief description of what we who look at failed jobs see consistently when jobs go bad. We also hear a fair amount of “I’ve been doing it this way for years and never had a problem.” Nobody is saying that each and every time you don’t take the appropriate measures to ensure a successful installation, a failure will occur. The reality is only a small percentage of jobs where proper installation practices have not been followed will fail. These failures may be near term, after a few years, or long term, 15-20 years. In most instances, either the home has been sold or the building remodeled, and who installed the floor will be long forgotten. But, many will fail and if you are fortunate enough to still be around you may find yourself unfortunate enough to be fixing problems that remained masked for many years. You would be surprised at how long you can be held accountable for your actions; it certainly is longer than the one year most think, depending on the state you live in. Why take a chance on failures? Follow the instructions and put it in right the first time.