Ceramic tiles have been used in wet installations all throughout history from the Roman baths to today’s commercial kitchens. This article will discuss the use of tile and waterproofing in three commonly executed and difficult wet installations: Showers, steam rooms, and exterior commercial decks. There are many more demanding wet tile installations like pools, spas, commercial kitchens, balconies, exterior walls, and water features that deserve a future article. If an installation is designed and correctly executed, most wet tile installations can last the life of the structure.  

Waterproofing Showers 

The key to a wet installation is proper water management. The degree and type of waterproofing is dependent on the type of installation. An excellent example of good water management principles is the traditional mortar bed shower pan. The pre-slope creates the needed slope to the drain at ¼” per foot slope. Next, the waterproofing is installed, most often in this installation a chloraloy or PVC shower pan liner is installed over the pre-slope and up the walls and over the curb, a minimum of e 3” above the finished curb as specified or required by code. Since the shower pan liner is not typically bondable, a wire reinforced mortar bed is installed over the shower pan and floated just below the thickness of the tile being installed below the drain. The mortar bed makes an excellent bondable substrate for tile. At the walls, the shower pan is covered with an appropriate backer board, such as cement board or a mortar bed.  

Fasteners for the cement board or lath for a mortar bed should be limited to the top 1” of the pan material coved up the wall. The traditional mud (mortar bed) walls will be installed over building paper or a vapor retarder membrane, then lath and a scratch and brown mortar bed. For proper wall-to-floor waterproof transitions: The backer unit, with or without the vapor barrier depending on the type of backer board, overlaps the shower pan, so any water or moisture that gets through the tile installation is drained down the backer board or vapor barrier into the shower pan. The water hits the sloped waterproofing and goes into the drain weeps, into the drain. Excellent water management principles: From the shower head of water, ship-lapped membranes, and slope to evacuate the water into the drain. Today’s innovative trench, integral and traditional drains allow for many alternatives to this traditional method but installed correctly, they all perform extremely well. It is all about managing the water. 

Waterproofing Steam Rooms 

A similar but very different installation is a steam room or steam shower. Steam rooms must manage the water like a mortar bed shower, but proper steam room design involves different construction principles, including slip joints in corners, sloped ceilings, and seating. Ceilings should be sloped a minimum 2” per foot to avoid condensate dripping onto occupants; sloping ceiling from center can minimize the amount of rundown on walls.  

A few years ago, the TCNA Handbook committee made some very important changes to the waterproof membrane application requirements in the TCNA Handbook steam room methods: SR613 and SR614. Steam rooms or steam showers designed for continuous use applications should specify a low perm waterproof membrane (a waterproof membrane meeting ANSI A118.10 and with a water vapor permeance rating of 0.5 perms or less when tested per ASTM E96 Procedure E, tested at 90% relative humidity and 100°F). When a waterproof membrane with a water vapor permeance rating greater than 0.5 perms is specified, a vapor retarder behind the wall assembly is required. And, the vapor retarder must have a water vapor permeance rating of 0.1 perm or less when tested per ASTM E96 Procedure A, tested at 50% relative humidity. This assures that the waterproof membrane can perform in the type of conditions to which it will be exposed in steam room or steam shower. If it can’t pass E96 method E, a vapor barrier must be added to the assembly. When installing commercial steam rooms, consult your setting material and backer board manufacturer, so you understand the proper assembly needed for your successful steam room or steam shower project.  

Waterproofing Exterior Decks  

A large exterior tiled deck may sound very different than a shower pan but the principles are same, it’s all about the water management. It is about getting the water off the deck surface as quickly as possible, to reduce freeze/thaw and possible slip issues. Both exterior deck methods in the TCNA Handbook F103 & F103B are very similar and both, if executed correctly, give the best water management assembly for an exterior installation of a tile deck. Both start with a properly sloped substrate, in the case of commercial construction that would typically be concrete. The concrete is sloped to a drain or off the exterior deck at ¼” per foot. Then a primary roof membrane is installed, sloped to drain either into the drain or off the deck. All exterior installations must also be waterproofed behind the finish material on the wall. In the case of stucco, brick, or wall siding, the deck’s primary waterproofing should cove up the wall and terminate 4” to 6” up behind the wall building paper, weather-resistive barrier, or similar drainage plane in the wall assembly. 

Next, on top of the horizontal primary membrane a 1” drainage layer of crushed stone with filter fabric on top or a drainage mat with filter fabric already applied is installed. This drainage on top of a primary membrane is an important and frequently overlooked step. It is critical, for best performance in freeze/thaw areas. Water will take the path of least resistance, it wants to go to air, when properly sloped, the drainage layer helps move the water efficiently to the drain. Next, a wire-reinforced unbonded mortar bed is installed, followed by an optional secondary ANSI A118.10 waterproof membrane, a bond coat, and tile.  

The optional secondary ANSI A118.10 waterproof membrane may be specified to prevent moisture intrusion into the mortar bed. Some contractors prefer keeping moisture close to the tile surface, so it can evaporate away, rather than allow water into the mortar bed. Without the secondary waterproof membrane, this large exterior deck performs the same as the tile shower pan or steam room pan. Water or moisture, such as rain, wets out the tile and setting material, goes into the mortar bed, soaks down to the waterproof membrane and drains into the drain.  

All three of these tile installations require properly installed TCNA method EJ171 movement joints. It is essential in wet areas, to install tile movement joints in showers, steam rooms, and exterior decks. While ceramic tile are not affected by moisture or water, they do have some absorption. Tile is as small as it will ever be when it comes out of the kiln. We must allow for movement due to changes in the assembly due to tile absorption, moisture, and thermal changes in all installations of tile, but this allowance is critical in wet areas.  

Read up on solutions to common moisture problems

Installing tile in demanding installations like showers, steam rooms, and exterior decks is not difficult, but it is different. A failed installation in a wet area can be very costly to the installed area, adjoining areas, and the building. Installers should really get credit for a well-executed wet areas installation. It takes an understanding of water management, proper product selection, planning, experience, quality installation skills, and a clear understanding of industry guidelines and standards.