Installing a shower or steam room relies heavily on the products used to make it waterproof. Properly choosing and correctly using these products are extremely important when it comes to making the project a success. For example, should a contractor choose a sheet- or liquid-applied waterproofing membrane for the project?

“It’s a question of installer preference—whichever system is chosen needs to comply with ANSI A118.10,” said Tom Plaskota, technical support manager, Tec. “The benefit of using a liquid system lies in the time element, as it dries quickly and is typically faster to install.”

Steve Taylor, director of technical and architectural marketing, Custom Building Products, echoed these sentiments. “Steam rooms require that the waterproofing membrane have a low perm rating (less than 0.5 perms) and so a membrane must be selected for its low-perm rating. Sheet (fabric) membranes do not have a dry time consideration, but require more skill and time to measure, cut, fit, apply corners and join sheets together. Liquid-applied membranes are easier to install and form a true monolithic membrane throughout the shower.”

Tim McDonald, vice president, Parex USA, noted that systems have advantages and disadvantages depending on the skill of the installer. “The plus side of using liquid-applied waterproof membranes is they’re monolithic—no seams and no cutting involved, so there’s less likelihood of a breach in the waterproofing system. With a sheet good, when you come to a corner you have to bend it and that means you have to cut it. Every time you cut something, you’re creating a possibility of a breach for the water to get into.”

According to Duane Farley, Loxcreen Flooring Group’s national account manager, pro channel, steam rooms require stricter standards than a typical shower install. “I don’t think [many] manufacturers of liquid-applied waterproof membranes recommend the product for use in steam showers. Using a mat such as ProVa mat, which is recommended for steam showers, is a safe install with no worries of leakage whether it is used in a steam shower or a regular shower.”

Application errors 

Common mistakes installers may make when working with waterproofing membranes can cause the integrity of the installation to fail. When installing traditional pan liner systems, these include “ignoring pre-slope installation, plugging drain weep holes with mortar and fastening tile backerboards through the liner on or below the curb,” said Sean Gerolimatos, technical director, Schluter Systems.

He added, “Leaving out the pre-slope and plugging the weep holes will cause the mortar bed to remain saturated, increasing the risk of efflorescence and mold growth in the system. Penetrations through the liner on or below the curb will result in leaks that damage surrounding building materials like wood framing, gypsum board ceilings, etc.”

Farley stated that following manufacturer recommendations is essential. “When using a fabric membrane with molded inside and outside corners, it would be impossible to have a failure when installed to manufacturer recommendations.”

Taylor said, “The most common mistake is spreading insufficient liquid-applied membrane over the surface and not properly seaming sheet (fabric) membranes. When applying liquid membranes it is important to make sure it is continuous with no holes or voids. If there are any, an additional coat should be applied. Many liquid-applied membranes require mesh reinforcement in corners and change of planes. Make sure you are following the coverage rates of the product you are installing with a uniform coating thickness.”

Added Peter Nielsen, co-founder of USG partner MGNT Products Group, “Failure to use reinforcing fabric where required can result in cracking of the membrane at these critical areas, leading to the subsequent penetration of water into adjacent wall cavities and building materials. In addition, many manufacturers of liquid-applied membranes have very specific wet and dry coat thickness criteria. Not following the written installation instructions regarding application thicknesses can compromise the performance of the membrane and in many cases determine success or failure.”

McDonald said applying too much liquid is a “rookie mistake” common among inexperienced installers. “They reason that if a little is good then a lot is better, and that’s not true. We always stress to installers that if you do get a leak, it’s going to happen at one of two places—either the wall-to-floor juncture or at the drain, because those are the areas you’re making changes. Then the installer’s tendency is to really pack the rubber in there.”

However, he added, this assumption leads to problems. “Latex-based liquid (which is 95% of what the market is for liquid-applied membranes underneath tile) cures from the topside down, forming a skin over the top where the air hits it. That means everything below it has to dry out at a slower rate because the water is evaporating through the top side. Since it’s already sealed, putting on too much liquid could take a long time—and I mean months—for it to cure out.”

Ensuring complete coverage

Plaskota said the best way to check the integrity of the waterproofing system is to run a flood test or water test. “One important part of any waterproofing application is to check the specific product for preparation, application and cure times. After the appropriate amount of time, a visible inspection can be performed to detect any surface issues, and a water test should be performed. If the cure time has not been reached, damage can occur during the water test or tiling stages. However, it is much easier to make a repair during the installation process than months later when additional damage can occur.”

Many inexperienced installers believe grout and sealers can serve as waterproofing, but Farley said this assumption is wrong. “Many think if you use ceramic tile and grout, water/steam will not penetrate the system, but water will penetrate concrete, given enough time and volume.”

Added Taylor, “Tile and grout are not for waterproofing. Penetrating sealers placed on grout do not stop water penetration. If the tile installation needs to prevent water from getting into adjoining spaces, a waterproofing membrane must be installed under the tile.”

Gerolimatos noted that having an approved waterproofing system beneath the tile is vital to the integrity of the installation. “Installers can do themselves a big favor by taking the time to educate their customers about proper waterproofing and the longer term benefits of using complete systems.”

Considerations for steam rooms

Seeing as steam rooms produce an incredible amount of moisture compared to showers, there are certain things an installer should look for when choosing products specifically for steam room use.

“The Tile Council of North America (TCNA) has added a water vapor permeance criterion to the requirements of the TCNA Steam Shower Methods,” explained Nielsen. “Contractors should look for products that meet the requirement of 0.5 perms or less per ASTM E96 Procedure E, tested at 90% relative humidity.”

Shower waterproofing materials are not likely to be sufficient for steam rooms unless specifically stated, stressed Gerolimatos. “Vapor particles are much smaller than water droplets and can penetrate through openings and pores that are too small for water to pass through. When vapor particles pass through a shower wall and enter into the cavity, they can bond together to form water again and cause significant damage and mold growth inside the wall cavity. The ANSI 118.10 standard for bonded waterproof membranes was developed to provide a framework for determining the suitability of these products to serve as barriers for liquid water only.”

Nielsen added, “In determining whether a specific product meets the ‘low perm waterproof membrane’ criteria of the TCNA, one needs to know the test method and the procedure. For example, ASTM E96 Procedure A is typically conducted at 73.4 degrees Fahrenheit and 50% relative humidity, while ASTM E96 Procedure E is conducted at 100 degrees Fahrenheit and 90% relative humidity, which best approximates the conditions of a steam shower. This means if a manufacturer reports a perm rating of 0.5 perms per ASTM E96, it is not enough information to determine if the product meets the [steam room] requirement.”

Farley shared these tips: “Make sure you follow TCNA guidelines for steam showers. The ceiling should be sloped 2" per running foot to avoid water dripping on occupants. It can be sloped from one side to the other or sloped to the center of the shower to avoid extra water running down the walls. The ceiling should not be over 8' high as it will take a larger steam unit to create enough heat at seat level.”

In the end, a proper installation comes down to not being afraid to ask questions if you are unsure of something. “It takes just as long to do things right as it does to do them wrong,” Plaskota said. “When choosing which waterproofing product to use, talking to the manufacturer’s technical representatives and gathering their knowledge can make the difference between an effective installation and an installation failure.”

Nielsen noted, “It can’t be emphasized enough that the most common mistakes are a result of not following the manufacturer’s installation instructions and industry standard guidelines. Make sure the right product is used for the application, and then consider where in the chain of events the quality control takes place for a given product.”

According to Taylor, “The waterproofing membrane is part of a system; it is not a standalone product. It is important the substrate is prepared properly to receive the membrane. It is also important that bonding mortars compatible with the membrane are used to install tile to the surface of the membrane. Be sure to fully read and follow the manufacturer’s directions. When possible, use a complete system from the manufacturer.”