Let me preface this article by saying it gets a little complicated as it goes on. Everyone likes the simple version of things and I have attempted to make it as simple as I know how. Understanding membrane uses and limitations is very important to your financial well being and is the purpose of this article.
Earlier in my career I would have to describe myself as a skeptic about the added value of using membranes in every tile installation. Product options were very limited and performance standards were non-existent. Over the course of time, construction methods and practices have changed, in some cases dramatically. Buildings are constructed with less time for acclimation of the structure and use a much tighter building envelope for energy efficiency.
To further complicate the issues, we are presented with specifiers and the electronic media educated consumers are increasingly looking for crack free, waterproof and quiet ceramic tile floors, sometimes all three. The needs of these structures and the desires of the end user have been noted by manufactures that develop products seeking to accommodate both the building practices and the desired increased performance of the installation. This is especially true when it comes to sound attenuation in multi-unit buildings which is mandated in many areas of the country under building codes. Mandated energy codes for a much tighter building envelope can cause problems unless areas receiving water or high moisture vapor are properly managed through the use of appropriate waterproofing products. Add to those issues the rightful desire and expectation for long-lasting crack-free floors in structures that are not allowed to properly acclimate and you have a plethora of reasons to use a membrane that did not exist 20-25 years ago.
Products made to Industry Standards can be counted on to perform when used in the proper application and appropriately installed. However, there is a long history of failure when using products that don’t meet appropriate standards such as roofing felt, sheet vinyl, scribing paper, and plain or scrim reinforced Kraft paper for various membrane applications.
The sound reduction market is probably the worse when it comes to understanding use of products. In days past most membrane claims revolved around improper installation. With the increasing amount of products available and their complexity, from my experience, there is an increasing amount of claims from not only products that do not meet standards but inappropriate use of those that do. There are published standards for ceramic tile and most tile related products that help level playing field. However, you can find substantial differences in their recommended use even when meeting standards.
In short, all products meeting the test requirements of standards are not created equal.
The product standard for waterproofing is the American National Standard Specifications for Load Bearing, Bonded, Waterproof Membranes for Thin-set Ceramic Tile and Dimension Stone Installation A118.10. This standard was developed to provide specifiers and installers with the minimum criteria necessary for a material to function as a barrier to positive liquid water migration in a load-bearing, bonded, thin-set installation of ceramic tile and dimension stone. This standard applies to trowel applied, liquid, and sheet membranes. Waterproof membranes for thin-set ceramic tile and dimension stone installations function as barriers to positive liquid water migration. Products meeting this standard are not designed for moisture reduction such as a slab under hydrostatic pressure.
The intention of waterproof membranes meeting tile standards is to stop liquid water from going into the substrate or entering the wall cavity. The waterproof aspect of testing under this standard revolves around preventing the passage of liquid water for a period of 48 hours. This means not all waterproofing products are necessarily suitable for prolonged submerged applications. There are also no reporting requirements relative to the passage of moisture vapor in an application, such as a steam shower. The amount of moisture vapor passage into the wall cavity can vary greatly dependent on use of the steam shower. Some products are suitable for 24/7 operation of steam units, most are not.
For crack isolation there is the American National Standard Specification for Crack Isolation Membranes for Thin-set Ceramic Tile and Dimension Stone Installation ANSI A118.12. This standard was also developed to provide specifiers and installers with the minimum criteria necessary for a material to function as a deterrent to crack propagation from the substrate through the finished thin-set tile or stone installation. Additional tests, which are not a requirement of this specification, may be run when requested for a particular project. Depending on the scope of the job, additional testing using the exact materials for that project which can be a very prudent decision.
The standard test method under this specification uses 4”x8” quarry tile to check for a membrane’s crack-bridging abilities. Anyone who has installed quarry tile knows it is a very elastic product as far as tile goes. It typically has a higher breaking strength than the porcelain tile more commonly used with membranes. Crack isolation membranes for thin-set ceramic tile and dimension stone installations are intended to isolate the tile or stone from minor in-plane substrate cracking. Membranes covered by this specification can be bonded to a variety of manufacturer-approved substrates under ANSI specifications. In some cases, the trowel-applied products may also be used as the adhesive for the ceramic tile or dimension stone. Other products used within the scope of this specification are allowed to cure or are applied as sheet goods and are then used as the substrate for the application of ceramic tiles and dimension stone by traditional methods and materials.
Cracks are allowed in the grout joints only when using a 118.12 product. There are two performance levels under the crack resistance portion of the test. For a standard-duty rating, the crack may occur after 1/16” of movement but before 1/8”. For a high-performance rating, the cracked joint may not occur till after 1/8”. There is no ASTM C-627 Robinson Floor Testing required under this standard. That particular test is used to provide a duty rating for a specific floor system ranging from Residential to Extra Heavy traffic. Any representation for suitability for use in a given application comes solely from the manufacturer. None of the performance testing under this standard uses stone as a specimen. Use of some Crack Isolation membranes can actually prove problematic to very soft stones such as travertine under moderate to heavy traffic conditions.
Standards for sound reduction membranes have been a goal of the industry for a number of years. In the most recent standards meeting, the American National Standard Specifications for Bonded Sound Reduction Membranes for Thin-set Ceramic Tile Installation ANSI A118.13 was approved by the committee and has received final approval from ANSI. It will be published in late spring or early summer of 2011 along with the numerous other changes approved by the committee.
This A118.13, standard like all others, was developed to provide specifiers and installers with the minimum criteria necessary for a material to function as a bonded sound reduction membrane when used with ceramic tile. Bonded Sound Reduction membranes for thin-set ceramic tile installation lower the transmission of sound from one room to the room below. Membranes covered by this specification are bonded to a variety of manufacturer-approved substrates covered by ANSI specifications. Products within the scope of this specification are applied below ceramic tiles by traditional methods and materials.
Dimension stone is a product of nature with a wide variety of inherent characteristics including veins, fissures, starts, and dry-seams. These characteristics may make the stone tile relatively fragile and susceptible to cracking and chipping when exposed to traffic. This susceptibility can be even more predominating when stone is placed on sound reduction materials, which are almost always resilient or compressible by nature. This sound standard was created specifically for ceramic tile.
If used for dimensional stone, additional testing would be required to establish suitability of use. The new specification describes the test methods and minimum requirements for sound reduction membranes for thin-set ceramic tile installation. It should be noted that while sound reduction membranes are intended to minimize the transfer of sound from one room to the room below, it is only one part of the overall system. Substrates, flooring material, ceiling assemblies, etc., will all affect the overall values. It is important when dealing with a sound reduction membrane that perimeter joints are properly located and filled as per the manufacturer’s instructions. The individual manufacturers, project engineers, and architects should be consulted, per Tile Council of North America (TCNA) recommendations, regarding their requirements for expansion and control joint material and placement.
There are two additional caveats that are very important to consider when using membranes under this standard. First, the floor performance level to pass this standard is a residential rating under the ASTM C-627 Robinson Floor Tester. The second and equally important consideration is the test uses a TCNA high performance thinset mortar. A TCNA high performance mortar is defined as ANSI A118.4 compliant latex modified thin-set mortar that has been identified by the TCNA Grout and Mortar Subcommittee as being capable of achieving a 28-day impervious mosaic tile shear bond strength greater than 450 psi. This is not your everyday thinset and would be considered a premium product.
So why does any of this matter? Quite simply, if there is no standard for any given product or installation then there is no expectation of performance other than that implied by the installer or manufacturer. As structures grow more complex in design and performance, expectations grow. We are certain to see an increased usage of membranes for their various attributes, be it for waterproofing, crack suppression, or sound reduction. There is likely no one company or one membrane that serves all conceivable situations. Structures and their attributes are complex as are the products that go in them. Pick some products from your favorite manufacture and learn them well, you need to!