You’ve found the perfect choice for your new shower wall or bathroom floor tile, and you’re ready to start your install! It’s a common assumption among homeowners that tiles are waterproof and water can’t pass through tiles and into the substrate once grout has set.
Unfortunately, that’s only partly true.
While tiles themselves are largely water resistant, tiled areas are fairly porous thanks to the surrounding grout. While treating grout joints with penetrating sealers can slow down water intrusion, it will not eliminate it completely.
That’s why bathroom and shower tile waterproofing methods and insulation systems are needed when you expect to have a good amount of water or vapor in your room. We’re covering the best methods for tile shower waterproofing and preventing moisture issues and damage in this How To Guide!
You'll feel even more confident in your amazing tile choices like our Emerald Hexagon Glass Mosaic, knowing that your shower tile is as waterproof and guarded against moisture and leaks as possible!
Prevent Moisture Issues – Why Shower Tile Waterproofing Is Important Before You Install
The water-resistant nature of tile makes it the preferred material for moisture-prone areas like showers, tub surrounds, and bathroom floors, but there are two potential problems to consider when installing tile in a wet and humid environment: water vapor that can diffuse into the walls or floors or bulk liquid that can come from leaks. Water vapor is an invisible enemy that can migrate through tile settings and cause moisture problems without being apparent. And while bulk water can sometimes evaporate and exit via the air handling systems, any remaining liquid also creates the perfect condition for mold and mildew to grow.
In the most humid rooms of a house, it is a huge mistake to overlook water insulation systems when installing tiles, especially in showers and steam rooms. If you don’t have the patience for insulation or simply think tiles are impervious, think twice! Remember that water insulation systems are relatively inexpensive compared to those costs you would have to pay later on. We’ll go over different types of water insulation systems in a minute.
But first…
What are the Consequences of Moisture to my Home?
Moisture is an issue that threatens not only our homes but also our health on a variety of different levels. They can be caused by leaks, improper tub and tile shower waterproofing, or lack of adequate ventilation. Below are some of the impacts of allowing moisture or leaks inside your home:
- Mold and Mildew –
Mold and mildew are some of the biggest problems caused by moisture. Aside from the constant cleaning required to keep it at bay, having mildew building can actually be the cause of major health issues. According to a study by The Mayo Clinic in 1999, nearly all chronic sinus infections in the United States (about 37 million) were caused by mold. Due to harmful toxins produced by fungus, mold is also known to trigger allergies, dermatitis, and even asthma attacks. Not to mention the coughing, sneezing and wheezing! Whether it’s a residential home or commercial setting, indoor mold is a serious health concern that can be prevented through properly sealing tile in areas prone to moisture.
- Pest Infestations –
It’s not just fungi that prefer wet and moist environments. Moisture also attracts common pests, including termites and carpenter ants, which are highly destructive to your home. Having pest infestations that go unchecked can lead to serious structural damage throughout your home, but you can prevent potential pest problems with a proper moisture seal.
- Structural Decay –
With excessive moisture, there’s a risk of decay to wooden frames that form the structure for most residential homes. Moisture is very likely to saturate the studs and framing components which eventually leads to rot and decay. Property inspections can help pinpoint areas of leaks and moisture that can lead to this kind of damage, and proper sealing is essential to prevention.
- Foundation Damage –
When water passes through tile flooring all the way through the substrate, it accumulates around the substructure. This sets up the perfect environment for cracking and uneven settling of your foundation, and can affect the entire level of your home! If you start to see flooring or tiles shift, or seams appear in your drywall, it can be a sign of damage to your foundation. Foundation repairs can cost tens of thousands of dollars so a little extra spent on water insulation systems is probably a better idea, right?
While there are solutions to all of the above problems after the fact - like an exterminator to rid your property of pest infestations, or dehumidifying to help with the health risks of breathing in mold - it’s always a better idea to prevent moisture issues before they start. After all, wouldn’t you rather avoid thousands of dollars to repair a damaged foundation if you could? These issues are commonly discovered when home inspections are held during the process of selling a house, and can have a significant impact on your resale value or even turn off potential buyers if the damage is too great. Even if you aren’t thinking of selling, it’s best to be proactive when it comes to protecting your home and your health, and one day your real estate agent might thank you! ‘An ounce of prevention is worth a pound of cure’ is a great way to think about the initial investment when it comes to waterproofing tile.
How to Avoid Moisture Problems on Exterior Bathroom Walls
When it comes to bathroom renovations, homeowners prefer to install tile for showers and bathtub surrounds. Using water resistant or waterproof tile is the easiest way to minimize leaks and water damage, but there are still moisture issues to consider. This is especially true for the grout between tiles, which is a permeable material. It allows water to pass through the wall or shower floor thanks to capillary action and may loosen the bind of tile over time. In hot climates, water that makes its way into grout will move towards drier areas - usually the outdoors - and can cause deterioration to the wall itself.
This usually happens on exterior walls as water vapor can evaporate fairly well in the empty wall cavity of an interior wall. That’s why the easiest way to prevent moisture problems in a bathroom is to avoid placing tubs and showers on exterior walls. Sometimes that placement is the only choice - in this case, there are water insulation systems that you can apply behind exterior walls to help minimize the chance of moisture damage.
Bathrooms are usually the most humid room in the house thanks to steam from tubs and showers, so this is where installation of water insulation systems most often come into play. These methods can also be used to help prevent moisture in other parts of the house, or anywhere tiles are exposed to water and extreme vapor.
An exterior wall shower with our Glossy Gold Hexagon Glass Mosaic Tile will be as efficient as possible with these shower waterproofing methods!
All right, we’ve covered some of the scarier consequences of allowing leaks or moisture build up, but let’s cover some of the water insulation methods for the most humid rooms in the house to improve durability, increase comfort and create a healthier indoor environment!
Tile Shower Waterproofing Insulation Methods to Extend the Life of Your Tile
Traditional Tile Shower Waterproofing Methods:
1. Shower Pan Liners 
Since your shower floor is a horizontal surface that’s regularly immersed in water, it requires some measures to prevent water from getting underneath and rotting your floor framing - the most effective being a shower pan. The purpose of a shower pan is to hold any water that goes through the grout and cement. The traditional method for installing tiled shower assemblies was described as a ‘water in / water out system’. It is basically the installation of a mortar bed over the subfloor that is sloped to weep holes in the drain. A waterproofing membrane (typically called a pan liner) is placed over this slope and clamped into the drain. Pan liners can consist of lead, copper, polyvinyl chloride (PVC) or chlorinated polyethylene (CPE). The picture shows an Oatey Shower Pan Gray PVC Shower Pan Liner.
Because pan liners are not designed to allow for the direct application of tile, a mortar bed must be installed to provide load distribution and a bonding surface for the tile. The mortar bed is sloped toward the drain, and then the tiles are installed using thin-set mortar.
Although this method is still used today, it is found to be ineffective as it causes water penetration through and around the mortar base. Installers who prefer using this method find this amount of water acceptable as long as the water makes its way towards holes at the base of the drain. However, that’s not always the case! Even with the proper slope below the liner, it’s impossible to keep water away from the mortar base. Guess what happens? Mortar is significantly hydrated, eventually breaks down, and mold starts to grow.
2. Hot Mop Shower Pans
The Ceramic Tile Institute of America recommends the hot mop shower pan method over the traditional shower pan liner we outlined above. To be honest, it’s just another method for installing tiled showers in a traditional manner! A ‘hot mop’ is the process of waterproofing with the use of mortar mix cement, asphalt, roofing felt and fiberglass mesh to build up a pan liner. After it’s heated in a kettle, hot asphalt is used to adhere layers of tar paper to cover the surface. Once the hot mop is complete, the mud of the tile setting is prepared and tiles are installed using thinset mortar.
One of the advantages of this method includes completing the whole process in a fraction of the time of the traditional method (which can also cut down on the overall cost). Since it is being applied in a liquid form, it also allows the pan liner to be applied in any shape or size unlike prefabricated methods. While it has benefits over the traditional shower pan liner, ‘hot mop’ is considered another ‘old school’ method! Although it’s an effective option that has been used for over 50 years, we’re going to cover new tile shower waterproofing methods that can be even more effective.
New Tile Shower Waterproofing Systems:
Manufacturers introduced new shower tile waterproofing systems in the late 80’s. These systems are directly adhered to the substrate and allow for direct application of tile. The first choice in choosing a waterproofing membrane is to decide between a prefabricated sheet and a liquid-applied membrane. The performance of both options is comparable, but the primary differences are in the installation process.
1. Liquid Membranes –
These are liquid-applied waterproofing products that require multiple coats with drying time in between. Unlike the sheet membranes below, there are no primers to apply, no seams to treat and transition through walls and corners. Liquid membranes are brushed, rolled or sprayed onto the substrate, in a similar process to applying paint. It is usually necessary to apply more than one coat to avoid voids or pinholes that allow water penetration to the substrate. Each product will have a requirement for the number of coats and how much thickness is necessary. Liquid waterproofing membrane is exemplified by Redgard Waterproofing Membrane by Custom Building Products, although there are also a number of other brands out there.
This is the easiest and cheapest option among the new waterproofing systems, which can be applied to any surfaces that come into contact with water or moisture. It can be used for both bathroom walls and floors, including horizontal areas exposed to moisture such as shower benches, shelving, half-walls, niches, and especially the shower floor. Some manufacturers even claim that they also serve as crack isolation membranes if applied thickly enough.
Pro Tips:
* When installing liquid membranes on horizontal surfaces in a shower such as shelves, half walls, and niches, ensure that these surfaces all have a slight pitch to the drain in addition to applying waterproofing. These surfaces are extremely susceptible to leakage!
* We still recommend installing a vapor barrier behind the substrate, especially if you plan on installing a steam generator in the bathroom.
2. Sheet Membranes –
When the waterproofing method is bonded to the substrate with a thinset mortar or other adhesive, it’s called a sheet membrane. The most common sheet membranes are plastic or elastomeric that have to be bonded to the substrate prior to installing tile. Sheet membrane has an advantage over liquid membrane because it’s very easy to see where the membrane is. Sheet membranes are exactly cut to size, avoiding any inadvertent gaps in the seal that may result in painting on a liquid membrane. You can attach wall and shower floor tiles to sheet membrane with a layer of thinset mortar in the same way you would set any tile.
On the walls - Some building codes also require these vapor retarder membranes to be installed between the studs and the backer board on outside facing walls, to limit moisture transfer into the framing in wet rooms.
On the floors – Most sheet membranes are pliable, and therefore easy to roll out onto your shower floor or any parts of a wet room.
Sheet membranes also differ from liquid waterproofing membranes in that they can also serve as uncoupling membranes. Some waterproofing sheet membranes can even act as an acoustic barrier as they provide sound proofing. Thanks to the design of a sheet membrane, the wet room is ready to tile as soon as the membrane is installed!
The most well-known example of sheet membranes would be the Kerdi Shower system by Schluter systems although many other companies like Noble Company, Blanke, Prove and others have waterproof shower sheet membranes.
Types of Waterproofing Membranes -
Keep in mind that the term ‘waterproofing membrane’ itself is actually misleading. No membrane is completely waterproof! The membranes that we refer to as ‘waterproof’ actually belong to a larger classification, which is called ‘Vapor Retarders’ and measured by ‘perm rating’. A vapor retarder can only limit the amount of moisture that can pass through it, not completely eliminate it. There are 3 vapor retarder classes that all waterproofing membranes fall into;
Class 1: 0.1 perm or less
Class 2: 0.1-1.0 perm
Class 3: 1.0 – 10 perms
Most tile shower waterproofing membranes will fall into Class 2, however some can end up in Class 3 as well. The lower the perm rating, the less moisture will get through the membrane!
Where to Install Waterproofing Membranes
The main influence on the location of a waterproof membrane is the climate. As a general rule, moisture tends to migrate from areas of greater (warmer) concentrations into areas of lesser (colder) concentrations. Or in other words, cold-climate wall assembly dries to the exterior and hot-climate wall assembly dries to the interior.
In areas where the climate is cold in the winter, the vapor retarder should be installed on the inner side of the wall near the warm interior space — or on the warm side in winter. In humid climates or areas where there is extensive use of air-conditioning, a vapor retarder should be installed on the exterior side of the wall.
As a pro tip, try to avoid shower niches or areas where water tends to gather on an exterior wall. If there’s no alternative, a pro tip is to make the horizontal surfaces of these cubbies sloped to shed the water back into the shower!
- Waterproof Foam Tile Backer Boards
Another method is to install foam backer board panels, where the waterproofing method is the same as the membrane systems mentioned above. They are waterproof on the surface rather than letting moisture absorb through the back of the board. These are made from extruded polystyrene foam and contain a layer of material on both sides for bonding tile mortar.
Foam wall boards can serve as a structural, load bearing substrate for tile as well as a waterproofing shower membrane. They come in various thicknesses to allow you to use them as building panels and backer boards. The most popular of these is the Kerdi Board by Schluter Systems. They are attached to the wall with special fasteners which are then covered with adhesive or small piece membranes to create a waterproof assembly.
2. Waterproof Foam Shower Bases
As an alternative to the outdated methods we covered above (old-school methods like shower pan liners and hot mopping), foam shower bases are sold as a kit that contains several components for the shower pan, such as a foam shower curb, membrane bonding shower drain, as well as corner and seam tape. There are standard size foam shower bases designed for either right or left-hand drain orientations. Since they are made from the same foam materials used for wall boards, these foam products are also easily trimmed to match your shower size and drain position by using simple hand tools, such as a utility knife!
A foam shower base is bonded to the subfloor with thinset tile mortar, making them simple to install. They always require the seams to be sealed with either special membrane corner pieces or strips of fiberglass tape, and then covered with waterproof adhesives.
You'll feel more freedom to get creative with your bathroom and shower know you've done as much tile waterproofing as you can - you can even mix things up like this pairing of our Ionic Copper Decor Impact B Rectified Porcelain Tile and Ionic Herringbone Copper Porcelain Mosaic Tile
Keeping wet rooms like bathrooms, laundry rooms, and even kitchens free of mold and other moisture-related problems can feel like an ongoing chore, but luckily you can cut them off at the pass by following some of these waterproofing steps for your shower or bathroom floor. Waterproofing tile walls and floors is the best way to reduce leaks and moisture issues that can build up over time and ensure your home stays safe and dry!
What have you found most effective for tile shower waterproofing and preventing moisture issues? Let us know in the comments!
