Shower Waterproofing 101 with Select Kitchen & Bath

As hurricane season rages on, we’re each of us reminded of the damage water can wield in our homes. Extremely corrosive to building materials, water leaks or flooding can cost thousands of dollars in repairs and can create an unsafe living environment if not addressed quickly and correctly.

While we cannot control the weather, we can take preventative measures against water damage, and we absolutely should when beginning new construction. This is especially important in the bathroom, where our daily showers have the potential to cause extensive—and expensive—water damage to the walls and floors of our homes.

To this end, I spoke with Derek Baxter, Bathroom Consultant with Select Kitchen & Bath, a kitchen and bathroom remodeling company operating in Northern Virginia and Washington, DC. I worked with Derek recently on an article covering various aspects of remodeling a master bath; this time, we spoke specifically on the best practices for waterproofing a shower and whether or not the seasoned DIY-er should take on a shower renovation project.

Shower Waterproofing Basics

When you think of shower remodeling, what comes to mind first? It’s likely an attractive tile pattern you noticed online or in a magazine. But tile, or “the fun part,” as Baxter deems it, is entirely secondary when it comes to proper shower installation.

“Tile and grout are cosmetic,” Baxter said. “Neither material is waterproof, so without a waterproof backing, water can infiltrate behind the wall or into the floor, causing mold growth and structural issues.”

There are various brand-name shower waterproofing products and systems on the market today, but most modern systems operate on the principle of creating a waterproof envelope behind the tile. When water seeps through the tile, it enters the envelope, where it flows into the drain.

To create the envelope, installers apply either a liquid membrane or a rolled sheet membrane to the walls behind the tile. They may also use waterproof boards or panels to construct the walls of the shower. Whether or not an installer chooses to tile the shower floor, the material of the shower pan (typically cast iron or acrylic) will affect planning the waterproofing system, as well.

It can all get a bit confusing.

The most important takeaway is this: Shower installations should always include some type of waterproofing system, and effective waterproofing requires a solid technical understanding of the particular system, the materials used, and strict adherence to installation instructions.

Shower waterproofing vocabulary

• Substrate: Refers to the material attached to the wall framing to which tile is applied (backer board), or the material underneath the shower floor (a plywood subfloor, for example).
• Tile backer board: Boards or panels designed to receive tile, constructed from gypsum, cement, pressed fiber and cement, or high density foam. There are dozens of brand names, which can be either water resistant or waterproof.   
• Pan: A pre-formed, waterproof unit that can be tiled, or a solid-surface unit made from cast iron, fiberglass, or acrylic that serves as the shower floor.
• Liquid membrane: A paint-on waterproofing material applied to water-resistant tile backer board to make it waterproof.
• Rolled membrane: A waterproofing material available as a rolled sheet, cemented to water-resistant tile backer to make it waterproof.
• Thinset: A bonding material similar to cement used to apply rolled membranes to tile backer board and to apply tile to that membrane.

Indications of improper installation

Normally, when you notice a leak at home, the best course of action is to call a reputable plumber. If the issue occurs in or around your shower (usually visible in one of the ways listed below), contact a professional remodeler.

Bubbling/soft drywall. Look for puckering where the shower tile meets drywall. This is a clear sign that the waterproofing has failed and water has seeped into the wall.

Water stains. If the bathroom is located above the ground floor, check the ceiling beneath. Water stains on the ceiling suggests failed waterproofing.

Cracked tile. Cracks in tile do not usually indicate an issue with the waterproofing, but with the backing material. Because tile is more rigid than the substrate it attaches to, it will crack as the substrate expands and contracts.

Waterproof Membrane System Comparison

For the purpose of this article, I asked Baxter to compare two popular brand-name shower waterproofing approaches: RedGard, which is a liquid membrane, and the Schluter-KERDI system, which uses either a sheet membrane or waterproof foam tile backer board. While preference varies among professionals, Baxter favors Schluter-KERDI for its relatively low margin for error and its “one-stop shop” materials list.

RedGard

RedGard is an easy-to-use, paint-on product that is relatively inexpensive. Some installers prefer it because it can be used with any water-resistant tile backer material. This allows the option for using backer material that is firmer than the foam waterproof boards of the Shluter-KERDI system, thus producing a more solid surface.

However, RedGard is not in itself a complete system. Installers must have the technical background to understand how to use it and other necessary materials properly.

Schluter-KERDI

The Schluter-KERDI system is more complex, but it’s a complete system including all component parts. Schluter-KERDI provides a wealth of educational materials for learning their installation process, and they also offer “shower kits,” or complete installation packages.

While Schluter-KERDI is the more expensive option, installers who have taken the time to become familiar and adept with the system can install showers and other tile projects quickly and efficiently with consistent results, saving on labor time to compensate for material expense.

Should You DIY or Call a Pro?

Waterproofing is one of the most important steps when installing a shower, as water damage can happen quickly without your knowledge and cost thousands to repair.

“You need it in your house and it’s great to have there, but the fact of the matter is that water is one of the most corrosive things you can have in a home,” Baxter said. “Any time you’re messing with water, you either want to make sure you really know what you’re doing, or you want to hire a professional.”

The seasoned DIY-er may have installed backsplash tile in the kitchen or completed a similar project, but constant exposure to water complicates the tiling process. If you choose to waterproof a shower yourself, a system using either approach discussed above will work, but you need to invest time in understanding that system, the component materials, and how they function.

Bottom line: For the best assurance of a water-tight shower renovation, contact a reputable remodeler. Our research team surveys thousands of homeowners a year, so you can hire a Best Pick company with confidence.

This article was crafted with the help of Derek Baxter, Bathroom Consultant with Select Kitchen & Bath, and Rick Kimmel, owner of select Kitchen & Bath.