To waterproof or not to waterproof, that is the question

The TCNA Handbook for Ceramic, Glass, and Stone Tile Installation highlights the building designer’s responsibility to know how each tile installation will be used and maintained, to avoid under-designing an area for the amount of water it will be exposed to. Courtesy of the Tile Council of North America, Inc. (TCNA).

I talk to many people who are not clear on when and where to use waterproofing under tile installations. The most surprising thing I come across is those who think that tile, grout, mortar and backer board are waterproof. Unfortunately, there are many failed installations due to the lack of waterproofing and improper waterproofing, so let’s look at when to consider using waterproofing under tile.

A good place to start is the Tile Council of North America (TCNA) Handbook, which addresses waterproofing in several places. There are specific sections such as the “Membrane Selection Guide” and the “Wet Area Guidelines” that discuss membrane usage. The Membrane Selection Guide outlines several different types of waterproofing, from non-metallic, lead, copper, CPE and PVC. There are also the ANSI A118.10 trowel-applied sheet or liquid waterproof membranes commonly familiar to the tile trades. Sometimes these are referred to as fluid-applied membranes. Once cured, these ANSI A118.10 membranes are designed to provide a continuous membrane that tile can be directly bonded to.

The Wet Area Guidelines section in the TCNA Handbook is a very useful for understanding the requirements for waterproof membranes. In addition to discussing the environmental exposure classification, this section also discusses proper slope required for wet areas, as well as the different types of drains, such as clamping drains and integrated bonding flange drains. One of the most important topics discussed in this section is performing the water test, commonly called a flood test or 24-hour test. Testing the ability for the area to properly hold water is an important factor to know prior to installing tile and is required by certain municipalities.

Many TCNA Handbook methods include the possible use of a membrane, leaving the design professional to determine whether one is needed, based on the expected water exposure.

Within the TCNA Handbook methods, such as F141-19, the diagram shows the option for a membrane and below the diagram it states, “*Use of a membrane is optional. See membrane options.” Does that mean a membrane usage is optional at the discretion of the installer? No, first, it’s important to understand the designed usage of the space and its Environmental Exposure Classification. The Environmental Exposure Classification section in the TCNA Handbook is often overlooked and yet it holds a wealth of information with regards to the intended usage of a space and thus the proper classification. These classifications are divided into two categories, residential (res) and commercial (com). Both the residential and commercial categories are further divided into seven separate classifications, each with its own expected water exposure.  

In the example TCNA F141-19, the area is designed with limited water exposure has a rating of Res1,2/Com1,2. If this space is going to be used as a commercial kitchen for instance, this area is typically designed with limited

Commercial kitchen maintenance practices vary widely. Some are routinely saturated during cleaning and require a membrane.

water exposure in mind, giving it a Com2 usage rating. The difference could be as simple as how the space is cleaned, do they intend to hose down the walls and floor? If so, the area would need to be designed for increased water exposure as outlined in the membrane options within the TCNA F141-19. Typically, in this type of situation, the flashing connections to the walls and any drains need to be addressed to create a complete waterproof system.

As you can see, there are a lot of considerations for the proper selection and use of waterproof membranes. If you have specific questions, contact a membrane manufacturer and they can help with the correct choice of material. Some manufacturers even provide job site support for the proper installation of their material. I’ll leave you with my simple rule of thumb, if it’s going to see water exposure, waterproof it – because in the end it’s cheaper than a failure.

William A. White

William A. White, is Certified Tile Installer #878 and aState Ambassador for the National Tile Contractors Association representing the states of Oregon, Washington, Idaho, Montana and Alaska. White is the Tile & Stone Team Leader for ARDEX Engineered Cements.