Bathroom Waterproofing—Floors, Walls & More

When it comes to bathroom renovations, many homeowners are tempted to splurge on the visible upgrades—luxury tiles, high-end fixtures, and stylish vanities—while cutting corners on the less noticeable but essential step of waterproofing. However, neglecting proper waterproofing can lead to costly problems down the road, including mold, rot, and structural damage. Because bathrooms are constantly exposed to moisture, investing in the right waterproofing materials and techniques is crucial for protecting your home and ensuring your renovation stands the test of time. 

In this guide, we’ll explore the best options for waterproof floors and walls, break down the steps involved in the process, and explain why waterproofing should never be an afterthought. With the right approach, you can enjoy a beautiful bathroom that’s built to last.

Waterproofing Bathroom Flooring

Best Materials For a Waterproof Bathroom Floor

The right bathroom flooring will not only stand up to daily splashes and humidity but also help prevent long-term issues like warping and water damage. Below are some of the top options for a waterproof bathroom floor:

• Porcelain or Ceramic Tile: These tiles are dense, non-porous, and highly water-resistant, making them a top choice for bathroom floors. When installed with proper grout and sealant, they provide excellent protection against moisture.
• Luxury Vinyl Tile (LVT) or Plank (LVP): Modern vinyl flooring is 100% waterproof, easy to install, and available in a wide range of styles. It’s also softer and warmer underfoot compared to tile.
• Natural Stone (with proper sealing): Options like slate, granite, or marble can be used in bathrooms, but they must be sealed regularly to prevent water penetration and staining.
• Sheet Vinyl: This seamless flooring option is completely waterproof and ideal for bathrooms, especially in homes with children or elderly residents.
• Concrete (sealed): Sealed concrete floors are durable, modern, and highly water-resistant. They can be stained or textured for a custom look.
• Waterproof Laminate: Newer laminate flooring products are specifically designed for wet areas and feature a waterproof core and tight locking systems to keep moisture out.

Traditional hardwood, standard laminate, and carpet can all absorb water, leading to swelling, warping, mold, and unpleasant odors. Even engineered wood, while more stable than solid hardwood, is not recommended for areas with frequent water exposure. For a bathroom that’s both beautiful and built to last, stick to materials specifically designed to handle wet environments.

Click here to learn about how much tiling a bathroom typically costs

What Waterproofing a Bathroom Floor Entails

Waterproofing a bathroom floor is a multi-step process that goes beyond simply choosing the right surface material. First, your contractor will ensure the subfloor is clean, dry, and level. A waterproof membrane—such as a liquid-applied membrane, sheet membrane, or waterproof backer board—is then installed over the subfloor. This barrier prevents water from seeping into the structure below. All seams, corners, and penetrations (like around drains and pipes) are carefully sealed with waterproof tape or caulk. 

Once the membrane is in place, the chosen flooring material is installed on top, with special attention to sealing grout lines and edges. In some cases, a final sealant is applied to the finished floor for added protection.

Waterproofing Bathroom Walls

Best Kind of Paint for Bathrooms

The best paint for bathroom walls is a high-quality, mold- and mildew-resistant paint with a semi-gloss or satin finish. These finishes are less porous than flat or eggshell paints, making them easier to clean and more resistant to moisture. Look for paints specifically labeled as "bathroom paint" or "kitchen & bath," as these contain antimicrobial agents to inhibit mold growth. Brands like Benjamin Moore Aura® Bath & Spa, Sherwin-Williams Duration Home®, and Behr Premium Plus Ultra® are excellent choices for bathrooms.

For more insights, read The Best Paint Finishes and Colors for Your Bathroom.

Is Wallpaper a Viable Choice for Bathrooms?

Yes, you can use wallpaper in your bathroom—but be sure to choose vinyl-coated options that are made to withstand steam and splashes. Avoid traditional paper-based wallpapers, as they can peel or develop mold in damp conditions. 

Even with moisture-resistant wallpaper, proper ventilation is essential to prevent issues over time. Consider using wallpaper on walls that are less likely to be splashed, such as above wainscoting or away from the shower.

Understanding What Must Go Underneath to Waterproof Walls

True waterproofing of bathroom walls, especially in wet areas like showers, requires more than just paint or wallpaper. Behind the finished surface, your contractor should install a waterproof backer board (such as cement board or foam board) instead of standard drywall. Over this, a waterproof membrane—either a sheet membrane like Schluter®-KERDI or a liquid-applied membrane—is applied to create a continuous barrier. 

All seams, corners, and penetrations are sealed with waterproof tape or caulk. This system ensures that any water that gets behind tile or wall finishes cannot reach the wall structure, preventing rot and mold.

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Additional Steps Your Contractor May Take to Waterproof Your Bathroom

• Sloping the shower floor toward the drain to prevent standing water: A properly sloped shower floor ensures that water flows directly into the drain rather than pooling in corners or low spots. This reduces the risk of water seeping into grout lines or beneath tiles, which can lead to mold and structural damage over time.
• Installing a waterproof curb and properly sealing shower thresholds: The shower curb acts as a barrier to keep water inside the shower area. By constructing the curb with waterproof materials and sealing it thoroughly, your contractor prevents leaks at one of the most vulnerable points in the bathroom.
• Using waterproof caulk or silicone at all joints and transitions: Joints where walls meet floors, or where fixtures meet tile, are common entry points for water. Applying high-quality waterproof caulk or silicone at these seams creates a flexible, watertight seal that accommodates movement and prevents moisture from penetrating behind surfaces.
• Applying a vapor barrier behind walls in particularly humid climates: A vapor barrier is a special membrane installed behind wall finishes to block moisture from passing through to the wall structure. This is especially important in humid climates, where condensation can build up and cause hidden mold or rot.
• Ensuring all plumbing penetrations are tightly sealed: Where pipes pass through floors or walls, gaps can allow water to escape into hidden areas. Your contractor will use gaskets, sealant, or special collars to tightly seal these penetrations, reducing the risk of leaks and water damage.
• Adding exhaust fans or improving ventilation to reduce humidity: Proper ventilation is essential for removing excess moisture from the air after showers or baths. Installing a high-quality exhaust fan or upgrading an existing one helps prevent condensation on walls and ceilings, reducing the likelihood of mold growth and maintaining a healthier bathroom environment

Why Bathroom Waterproofing Should Never Be Skipped

Skipping proper waterproofing may save money upfront, but it can lead to costly surprises later. With the right materials and approach, you’ll gain peace of mind that your bathroom is built to last. The most common issues are:

• Mold: Persistent moisture behind walls or under floors creates the perfect environment for mold growth, which can cause health problems and require expensive remediation.
• Decay: Water that seeps into structural elements can cause wood rot, weaken framing, and compromise the integrity of your home. Repairing this type of damage is often far more expensive than proper waterproofing from the start.
• Tile and Grout Failure: Without proper waterproofing, water can penetrate behind tiles and grout, causing them to loosen, crack, or discolor over time. This not only ruins the appearance of your bathroom but can also lead to costly repairs and the need to replace entire sections of flooring or walls.

Simply put, thorough waterproofing is a smart investment that shields your home, your health, and the money you’ve put into your renovation.

Everyday Tips to Prevent Moisture Damage in Your Bathroom

Even with the best waterproofing materials and techniques, daily bathroom use can still lead to excess moisture. To further protect your space and prevent long-term damage, it’s important to adopt habits and solutions that minimize humidity and water accumulation. 

Here are several effective strategies to help keep your bathroom dry:

• Install a high-quality exhaust fan and use it during and after showers. Effective ventilation removes humid air, helping to prevent condensation and mold growth.
• Consider a humidity-sensing fan that runs automatically when moisture levels rise. These smart fans activate as needed, ensuring your bathroom stays dry even if you forget to turn on the fan.
• Keep bathroom doors and windows open when possible to promote air circulation. Allowing fresh air to flow through the space helps moisture evaporate more quickly.
• Use bath mats and rugs that dry quickly and wash them regularly. Fast-drying, washable mats prevent water from lingering on the floor and reduce the risk of mildew.
• Seal grout lines and caulk joints regularly to maintain their waterproof barrier. Keeping grout and caulk in good condition prevents water from seeping behind tiles and into walls or floors.
• Check for leaks under sinks and around toilets, and address them promptly. Early detection and repair of leaks can prevent hidden water damage and costly repairs down the line.

Invest In Your Bathroom With Block Renovation

Waterproofing is one of the most important investments you can make in your bathroom remodel. At Block Renovation, we work with experienced contractors who understand the latest waterproofing techniques and use only high-quality materials. They will guide you through every step, from selecting the right products to ensuring every detail is installed correctly. 

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