What You Should Know About Waterproofing Your Tile—And What to Do if It’s Not

Audrey Bruno
Written by Audrey Bruno
Updated May 27, 2022
Bright clean shower
Photo: Justin Paget / DigitalVision / Getty Images

If you’re struggling with a shower that always smells funky, it might be because your tile isn’t actually waterproof

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Despite what many believe, the tile and grout in most showers isn’t waterproof all on its own. It’s actually protective membranes and sealants installed before and after new tile. 

This sealant is key to preventing wet areas and mildew from developing and will keep your morning shower a relaxing way to wake up.

Why is Waterproofing Tile Important?

Waterproofing tile in rooms prone to moisture will protect your home from water vapor and the issues it can lead to.

Mold and Mildew

Water that gets behind tile and into walls or floors can cause leaks and create the conditions for mold and mildew to grow. According to the Centers for Disease Control and Prevention, people who are sensitive to molds may develop symptoms like “stuffy nose, wheezing, red or itchy eyes, or skin.” Those with allergies and asthma are at risk for more severe symptoms like shortness of breath or fever. 

To prevent mold and mildew, make sure your tile is correctly waterproofed and your bathroom has a ventilation fan. For those who live in humid environments, a dehumidifier might be necessary to control humidity levels. 

Pests

In addition to mold and mildew, there are common household pests that are attracted to moisture that gets behind tiles and into the substrate. You might find some centipedes, termites, and carpenter ants—and the last two can be destructive to your home. If you have a pest infestation on your hands, you might need to call a local exterminator and repair any pest damage. However, don’t forget to remedy the moisture issue, or the pests are likely to return. 

Structural Decay

Moisture that travels through tiles and into the wooden framing and studs of a home can cause decay, rot, and fungus. 

Foundation Issues

Water that goes through the tile in a bathroom can find its way into the substructure and cause cracking and uneven settling in your foundation. You might have foundation issues if you notice tiles shifting or new seams in your drywall. Depending on the damage, foundation repairs cost between $2,010 and $7,060 on average. Waterproofing your tile could go a long way toward protecting your home’s foundation.

How Do I Find Out if My Shower Tiles Are Waterproof?

If your shower has a funky smell that won’t go away no matter how many times you clean, it’s probably because your tile isn’t actually waterproof. Wet areas or noticeable molding—whether on the shower walls or floor—are other signs this might be your problem.

The next error occurs when the tile setter overlooks mistakes made by the builder and plumber. They will install the wall board that they are comfortable with and float a sloped mud set pan over the vinyl liner in an attempt to provide positive drainage in the finished shower floor.

If there’s no standing water (often called a birdbath) in the shower pan when you turn off the shower valve, the shower pan must be working correctly, right? Many go on to compound the mistakes by not taking measures to install any waterproofing measures prior to setting the tile.

Quite a few bathroom tile contractors also will puncture the liner in critical areas on the curb and below the curb line inside the shower pan while fastening the wall board. Another requirement of a vinyl shower pan liner is a bed of pea gravel in the mud set around the drain, a step that pros or DIYers often ignore.

Should I Try to Waterproof My Existing Tiles or Start Over Entirely?

It all depends on the current state of your shower. If there are severe structural damages, it’s probably necessary to pull up the existing tile and grout and replace everything. 

Newer tile installations that haven’t received much use will be fine with a coating of liquid membrane or sealant. The only catch: you may have to reapply this sealant over the years.

How Much Will It Cost to Waterproof My Shower Tiles?

While shower waterproofing kits can be pricey, they’re worth the splurge to prevent costly repairs down the line. They include everything you need to complete the project—including sheet membrane and a shower tray—and can cost anywhere from $477 to $745, depending on the size and setup of your shower. 

Alternatively, you’ll pay much less for liquid membrane upfront—between $55 and $770—but may have to spend more on upkeep in the future.

Clean shower tiles
Photo: John Keeble / Moment / Getty Images

Types of Shower Tile Waterproofing Methods 

There are three main types of tile waterproofing methods, and the installation process for each varies. 

Sheet Membrane

Sheet membrane made of polyethylene is the most durable waterproofing system, but it’s not as DIY-friendly as other options. Before tile installation, the sheets bond with the substrate using an adhesive or thinset mortar. One advantage to sheet membrane is that you can easily tell where the membrane is. 

The sheet membranes are cut to size, which helps avoid gaps, and bathroom tiles can attach to the sheet membrane with thinset mortar. Note that some codes call for shower membranes between the studs and backer board on exterior walls. 

Foam Board

Foam boards are more costly than other options, but it’s lightweight and easy to install. 

The panels consist of extruded polystyrene foam on both sides and double as a backerboard and a load-bearing substrate. You’ll need special fasteners and adhesive to attach them to the wall. Applying a liquid-applied membrane over the parts and seams makes it fully waterproof. 

Liquid-Applied Membrane

Liquid-applied membrane waterproofing systems are the most cost-effective option and are easy to apply. However, they aren’t as strong as sheet membranes. You may use it as your main waterproofing system or pair it with other systems like foam boards.  

You can apply liquid membrane to the substrate with rollers, sprayers, or brushes, just like you would if you were painting. You’ll most likely need more than one coat to make sure the membrane is completely waterproof; allow each coat to dry before applying the next coat. Check the product label for the number of coats and thickness needed.

What Tools and Materials Do I Need to Waterproof My Shower?

Shower waterproofing kits include most of the materials you need to complete this project. And remember, all of this needs to be installed before laying down tile:

  • 1 shower tray

  • 2 shower curbs

  • 2-3 rolls of waterproofing membrane

  • 1 shower collar

Some kits will also include crack isolation membranes to prevent tile or grout from cracking. You can always buy this separately. 

From there, you’ll also need some common tools to complete the job: a paintbrush, a smoothing tool, and scissors for cutting the membrane. If you choose to hire a pro, they’ll have all the necessary equipment to get it done. 

Even if your shower is equipped with under-tile waterproofing, it can still be worth it to add an extra layer of security. For this, you’ll need your preferred brand of liquid sealant, a smoothing tool, and a bit of time to let it fully dry.

Is This a Project I Can DIY, or Should I Hire a Pro?

Once again, this is going to depend on the shower’s current condition. If it’s experiencing serious damage from years of insufficient waterproofing, you might need a total replacement. In these cases, it’s best to hire a tile installer in your area to guarantee everything is up to code so the same problems won’t reoccur. 

On the other hand, it’s easy to apply a layer of protection to a newly completed tile installation on your own.

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