Beyond Crack Isolation
May 17, 2007
For those of you not already familiar with crack isolation membranes, their purpose as stated in the 2006 TCNA handbook is to “act to isolate the tile or stone from minor in-plane substrate cracking.” Crack isolation membranes have saved many tile jobs from what would have been total failure. For more than 25 years, millions of square feet of crack isolation membranes have made tile surfaces workable in otherwise unworkable situations.
Although they’ve been around for years, it was not until 2005 that the ANSI Committee approved the A118.12 Crack Isolation Standard and installation methods were formally added to the Tile Council of North America (TCNA) Handbook in 2006. In order to meet ANSI A118.12, a crack isolation membrane must pass six very important tests: 4.0 for Material Properties, 5.0 for System Performance, 5.1.6 for Shear Strength After Accelerated Aging, 5.2 Point Load Test, the 5.3 Robinson Floor Test and 5.4 for System Crack Resistance. Specifying a membrane proven to meet the ANSI A118.12 standard with actual test results is critical to assuring a successful installation for years to come.
Standard performance vs. high performanceAlthough crack isolation membranes come in many forms - from sheet applied, trowel applied to liquid applied - all are not created equal in performance. Elastomeric sheet membranes generally outperform liquid or trowel applied membranes for durability, speed and crack bridging ability. According to the A118.12 system for crack resistance, these membranes are broken down in two categories: “Standard Performance” & “High Performance” Make sure you select a “High Performance” model for best results.
Not just for cracksI’m a little biased, but nothing beats a high quality, elastomeric sheet membrane for speed, high performance and durability. Products comparable to ECB, Strataflex, SAM3 and Super SAM are comprised of an elastomeric adhesive base bonded to fabric with backing paper to protect the pressure-sensitive adhesive. In addition to bridging cracks, they expand the use of ceramic tile by converting an unsuitably cracked floor to a new suitable tile surface, relocating movement joints to accommodate tile patterns, protecting marble and hardwood floors from harmful moisture, accommodating movement from radiant heated floors, helping prevent mold growth on tile and grout and, with a little chemistry and resourcefulness, some can make a great waterproofing membrane. Here is a rundown on some other applications crack isolation membranes have moved into over the years.
Waterproofing Membrane for Thinset ApplicationsBy adding a quality, impermeable binder, self-adhering crack isolation membranes can easily be converted to waterproof membranes utilizing a “double stick” lap joint. The advantage of these membranes is that they provide “the lowest profile, (elevation) of the tile installation when incorporating a waterproof membrane”. These products are great for exterior decks, shower pan liners, food courts in malls, restaurants, and bathrooms. Again I can’t stress enough the importance of meeting standards. In this case, when specifying a waterproofing membrane, you’ll want to ensure that the one you’ve selected meets ANSI A118.10 for load bearing, bonded, waterproof membranes.
The key advantage to a system like sheet-applied Strataflex is its durability, speed of installation and of course, its crack isolation qualities. Since this type of system is self-adhering, another advantage is that there’s usually no waiting for the system to cure. This means tile can be set immediately and water tested in 24 hours.
Another advantage to high performance elastomeric sheet membranes is that they have a consistent thickness and can go through extreme climate changes without drying out or cracking making them a great choice for exterior applications. Used in conjunction with pre-formed corners and double stick flashing tape, water tests can be conducted within 24 hrs, speeding up the building process.
Sound controlOne of the biggest benefits of elastomeric thin-bed membranes is sound abatement, but not without controversy. Floor systems that utilize elastomeric sound control membranes improve the acoustical performance of the floor/ceiling system typically used in high-rise or multi-family residential construction. Like its big brother the crack isolation membrane, sound control systems like SAM3 and Super SAM provide a lower profile in comparison to other sound control membranes for ceramic tile applications. Again, the key advantage to these systems is their durability, consistent thickness, speed of installation and of course, their crack isolation qualities. Quite an advantage when floor height and door thresholds are on-the-job issues!
Thicknesses range from 40 mils to 120 mils and are selected based upon intended application. As with crack isolation and waterproofing, there are acoustical properties that will factor into which sound abatement membrane you will use. Briefly, there are two types of ratings used to measure sound control. IIC (Impact Insulation Class) which is like the sound when a woman walks across a floor with high heels, and STC (Airborne Noise) which is like the sound of music coming from a stereo without a sub woofer.
So, the higher the STC & IIC ratings, the better the sound reduction, right? Yes, but with one important consideration: The current ANSI Standard does not necessarily reveal the TRUE components of the sound reduction assembly and IIC & STC test numbers can be easily manipulated to get unusually high numbers. For example, a bare 6” concrete slab without a tile assembly usually starts out with a IIC rating of 26 to 30. Some thin-bed elastomeric membranes rate their sound control membrane in the mid to high 60’s. An element in the testing assembly can contribute to higher ratings such as a sound rated ceiling assembly, 4” of insulation, double membrane, etc. You get my point. If you come across an acoustical membrane that quotes an IIC rating of over 60, a RED FLAG should be raised. Ask for written tests results including the composition of the testing assembly.
Fortunately there is hope. A new test protocol is in the works, ASTM E2179-03e. What the new protocol will accomplish is to define what the membrane contributes to the IIC (Impact Insulation Class). For example, if a bare 6” concrete slab has a rating of 26 IIC and the tile assembly with a sound control membrane is tested with a final result of 51 IIC, then the contributing IIC or delta rating is 25 IIC (51-26 = 25 ).
Mold and Moisture Vapor Transmission ResistanceMold, mildew and moisture can be an unhealthy and destructive force in your home and on decorative floor surfaces. The wicking of moisture carrying salts through a concrete slab can cause warping, pitting and discoloration in natural stone, grout efflorescence and adhesion loss in ceramic tile. It can also cause discoloration and warping on hard wood floors. This is often the case in coastal and low lying geographical areas as well as new construction projects in which the dynamics of a concrete slab are changed by initial exposure to HVAC (air conditioning or heating). When selecting companion products, be sure the manufacturer states its level of resistance to moisture. For example, ECB, Strataflex, SAM3 and Super SAM have all been field tested and proven effective for up to 10# MVT with 0 perms. The photo above demonstrates the MVT Protection ECB Membrane gives to a natural stone installation.
When specifying a membrane for crack isolation, waterproofing, sound abatement or other applications, be sure to consider components of a membrane system as well. For example, non re-emulsifiable primers will not only help protect against mold and moisture, but also assure a better bond between membrane and substrate to successfully withstand exposure to moisture from the ground up.
Hopefully you’ve learned a little more about the versatility of the crack isolation membranes. When using them for applications “Beyond Crack Isolation”, ask for real data and proof of performance to make your installation easier, limit your liability and assure you’re getting the best membrane for the job at hand.