There have been many waterproofing methods attempted, with some proving successful while others have failed. These efforts led to a decree by the Materials and Methods Standards Association (MMSA) authorizing the formation of a committee to establish standards. This resulted in an ANSI document: American National Standards Institute specifications for load-bearing, bonded, waterproofing membranes for thin-set ceramic tile and dimension stone installation, a document found under the heading "A-118.10."
In the standard found under MN.1, membranes are described in the introduction as barriers to positive liquid migration. In some cases, certain membranes can double as the bonding adhesive for the ceramic or stone installation. MN1.2 states that the ANSI standard applies to trowel-applied, liquid-applied, and sheet membranes.
Another important requirement in ANSI A118.10 is the testing for fungus and microorganism resistance, a requirement that is increasingly relevant in today's society. And of course, there are bond-strength, seam-strength, and water-resistance requirements.
There are many different membranes available, both in sheet and liquid form. Regardless of the type you choose, I would suggest you make certain it meets the ANSI standard.
Sheet membranes are generally composites made from chlorinated polyethylene, bitumen, or vinyl. The advantage of sheet membranes is that there is no waiting time required for curing or set-up. The ceramic tile or stone may be installed immediately. Sheet membranes have spun-bonded polyester fibers bonded to the sides of the membrane. This allows a thin-set procedure to be used in the setting of the stone or tile.
How thick?The thickness of the sheet membranes can be 20-, 30-, or 40-mil, so that no substrate depression is needed. Most sheet membranes do not require a floor primer prior to installation. Again, this results in a faster installation. Seaming methods are reasonably simple and time-friendly. Most sheet membranes require a bonding agent (either latex modified thin-set or mastic) to secure the membrane to the substrate. Others may be self-adhering. Usually, self-adhering membranes require substrate priming.
I would like to point out that waterproofing membranes, sheet or liquid, double as crack-isolation membranes. In effect, you get two values for the price of one.
Now for a word or two about trowel- and liquid-applied membranes. Liquid-applied membranes come in various chemical compositions, such as asphalt-modified, neoprene-latex elastomers reinforced with a polyester fabric; polymer liquids; cementitious fiber powder; polymer and fabric; and one-component urethane (the one-component urethanes can double as the bonding agent). Liquid and trowel systems vary in flood testing and minimum times allowed before setting the ceramic or stone. For example, one system says you may start installing after 8 to12 hours, while others may say 4 to 6, or "a few," hours.
With most liquid-applied membranes, there are preparation steps and procedures to follow, such as mixing the liquids and powders, and placing the reinforcing mesh. Both sheet membranes and liquid-applied membranes have a very high success rate when properly installed. Again, it is important to know if the products meet the A118.10 requirements. It is also important to follow the manufacturer's instructions regarding installation limitations.
Waterproofing has become a valuable part of the installation profession. Often, it becomes a debate between Divisions Seven and Nine as to who wants to install the waterproofing. Many tile contractors do not want the responsibility, and would prefer the waterproofing contractor do the work. Others actively seek this work, as it can be highly profitable.
Another point to consider is service requirements, which range from residential to heavy. The manufacturer should provide you with a service rating when their membrane is going to be used.
Becoming experienced in installing large-area waterproofing is not only profitable, but it is a step to gaining the experience and knowledge necessary to install sound-isolation materials as well. Sound isolation is becoming more of a factor in ceramic and stone installations. The savvy installer will always consider the profitability factor.