Waterproof Tiles: Which Tiles Are Truly Waterproof?

Tiles are widely considered a waterproof flooring option, but the reality is more nuanced than most homeowners realize. While certain tiles are essentially impervious to water, others absorb moisture readily, and the grout between every tile is the weakest link in any tile installation.

Understanding which tiles are genuinely waterproof, which need additional protection, and how to build a complete waterproofing system is critical for wet areas like bathrooms, showers, and laundry rooms. This guide breaks down the water resistance of every major tile type and explains what it takes to create a truly waterproof tile installation.

Are Tiles Waterproof? The Short Answer

The tile itself may or may not be waterproof depending on the type. However, a tile floor as a complete system is never inherently waterproof. Water can penetrate through grout lines, unsealed edges, and the substrate beneath the tile. A waterproof tile installation requires waterproof tiles, waterproof grout or sealed grout, and a waterproof membrane beneath the tile.

Let us examine each tile type individually.

Porcelain Tiles: The Most Waterproof Option

Porcelain tiles are the closest thing to a truly waterproof tile. They are made from refined clay fired at extremely high temperatures (2,200-2,500°F), which vitrifies the material into a dense, glass-like body. The result is a tile with a water absorption rate of less than 0.5% — the threshold that officially classifies a tile as “impervious” according to ASTM standards.

Many high-quality porcelain tiles have absorption rates as low as 0.1%, meaning they absorb virtually no water even when fully submerged. This makes porcelain the top choice for:

• Shower walls and floors
• Bathroom floors
• Outdoor patios and pool decks
• Laundry rooms
• Commercial kitchens
• Basements

Porcelain tiles are through-body colored, meaning the color and pattern extend through the entire thickness of the tile. Even if the surface chips, the exposed material matches the surface. This is another advantage in wet areas where wear and tear are common.

Glazed vs. Unglazed Porcelain

Both glazed and unglazed porcelain tiles are waterproof at the tile body level. The glaze adds an additional layer of protection and makes the tile even more stain-resistant, but unglazed porcelain is already impervious to water. For wet areas, glazed porcelain offers easier cleaning, while unglazed or textured porcelain provides better slip resistance.

Ceramic Tiles: Water-Resistant, Not Waterproof

Ceramic tiles are made from similar clay materials as porcelain but are fired at lower temperatures (1,800-2,000°F). This results in a less dense body with a higher water absorption rate, typically between 0.5% and 7%. Technically, ceramic tiles are classified as “non-vitreous” to “semi-vitreous” depending on their absorption rate.

What does this mean in practice? An unglazed ceramic tile can absorb a meaningful amount of water over time. In a constantly wet environment like a shower floor, this absorbed moisture can lead to:

• Mold and mildew growth behind or beneath the tile
• Weakening of the tile-to-substrate bond
• Cracking during freeze-thaw cycles (outdoor use)
• Staining from colored liquids that penetrate the body

Glazed Ceramic: A Different Story

The glaze applied to the face of ceramic tiles creates a glass-like barrier that is effectively waterproof. As long as the glaze is intact, water cannot penetrate the tile surface. This is why glazed ceramic tiles are acceptable for bathroom walls and kitchen backsplashes, even though the tile body itself is not waterproof.

However, the sides and back of glazed ceramic tiles are unglazed and can absorb water. This is why proper waterproofing beneath and behind ceramic tile installations in wet areas is non-negotiable.

Natural Stone Tiles: Requires Sealing

Natural stone tiles — including marble, granite, slate, travertine, and limestone — are inherently porous. Their water absorption varies widely by stone type:

• Granite: 0.1% to 0.6% (least porous common stone)
• Slate: 0.2% to 0.8%
• Marble: 0.2% to 1.5%
• Travertine: 1% to 5%
• Limestone: 2% to 12% (most porous common stone)

Without sealing, most natural stone will absorb water, stain, and potentially develop mold in wet environments. Granite is dense enough to perform reasonably well without sealing, but all natural stone used in wet areas should be sealed with a penetrating impregnating sealer.

Sealing does not make stone waterproof. It slows water absorption significantly, giving you time to wipe up spills before they penetrate. For shower and bathroom use, natural stone requires both a quality sealer (reapplied every 1-2 years) and a proper waterproof membrane system behind it.

Grout: The Weak Link in Every Tile Installation

Even if you install perfectly waterproof porcelain tiles, the grout between them is porous. Standard cement-based grout absorbs water readily, allowing moisture to reach the substrate beneath the tile. Over time, this leads to mold growth, substrate deterioration, and potential structural damage.

Types of Grout and Their Water Resistance

• Sanded cement grout: Most porous. Requires sealing. Best for joints wider than 1/8 inch.
• Unsanded cement grout: Slightly less porous than sanded. Still requires sealing. Used for narrow joints.
• Epoxy grout: Virtually waterproof. Does not require sealing. Excellent for showers and wet areas. More expensive and harder to apply.
• Urethane grout: Pre-mixed, flexible, and water-resistant. Does not require sealing. Good for wet areas and areas with slight movement.

For truly waterproof tile installations, epoxy grout is the gold standard. It is impervious to water, resists staining, and does not support mold growth. The downside is that it is significantly more expensive than cement grout and must be applied carefully, as it sets quickly and is difficult to clean once hardened.

Sealing Cement Grout

If you use standard cement grout in a wet area, sealing is mandatory. Apply a penetrating grout sealer after the grout has fully cured (typically 28 days for cement grout). Reapply the sealer every 6 to 12 months in shower areas and annually in other wet spaces. Even sealed cement grout is not truly waterproof — it is water-resistant at best.

Waterproofing Systems for Showers and Wet Areas

A waterproof tile installation in a shower or wet area requires more than waterproof tiles and good grout. The complete system includes a waterproof barrier between the tile and the wall or floor structure.

Sheet Membranes

Products like Schluter KERDI and NobleSeal TS are polyethylene sheet membranes that bond directly to the substrate before tile installation. They create an impenetrable barrier that prevents any water that passes through grout lines from reaching the wood or cement board behind the tile.

Sheet membranes are applied with thin-set mortar and overlapped at seams with special waterproof tape or sealant. They are the most reliable waterproofing method for shower walls and floors.

Liquid-Applied Membranes

Liquid waterproofing membranes like RedGard, Hydroban, and AquaDefense are painted or rolled onto the substrate in multiple coats. Once cured, they form a flexible, waterproof layer that bonds directly to cement board, concrete, or drywall.

Liquid membranes are easier to apply than sheet membranes, especially in areas with complex geometry like shower niches and benches. They typically require two coats with drying time between each coat.

Foam Shower Panels

Pre-formed waterproof foam panels like Schluter KERDI-BOARD and Wedi building panels serve as both the substrate and the waterproof membrane. Tiles are installed directly onto the foam panel, eliminating the need for cement board and a separate waterproofing layer.

These systems are increasingly popular for shower builds because they simplify the waterproofing process and reduce the number of potential failure points.

Shower Pan Waterproofing

The shower floor is the most critical area to waterproof because water collects there by gravity. Options include pre-formed shower pans (like Schluter KERDI-SHOWER-ST), hot-mopped or cold-applied membrane pans, and liquid-applied membranes over a mortar bed. Regardless of the method, the shower pan must slope toward the drain at a minimum of ¼ inch per foot.

Testing Tile Water Absorption at Home

If you are unsure about the water absorption rate of a tile you already own or are considering, you can perform a simple test at home.

1. Place a few drops of water on the unglazed back of the tile.
2. Wait 5 minutes and observe.
3. If the water is absorbed quickly (within 1-2 minutes), the tile is highly porous and not suitable for wet areas without significant waterproofing.
4. If the water beads up and remains on the surface after 5 minutes, the tile has low absorption and is suitable for wet areas.
5. If the water slowly absorbs over the 5-minute period, the tile is semi-vitreous and may be acceptable for wet areas with proper waterproofing beneath it.

This is not a precise scientific test, but it gives you a useful indication of how the tile will perform in a wet environment.

Best Waterproof Tile Choices by Room

Showers

Use porcelain tile with a textured surface for slip resistance. Pair with epoxy grout and a sheet or liquid waterproof membrane. Avoid natural stone unless you are committed to regular sealing.

Bathroom Floors

Porcelain or glazed ceramic with a waterproof membrane beneath. Small-format mosaic tiles work well for shower floors because the extra grout lines add traction.

Kitchens

Porcelain or glazed ceramic is sufficient. A waterproof membrane is not typically required for kitchen floors, but it adds an extra layer of protection against dishwasher leaks and spills.

Laundry Rooms

Porcelain tile with sealed grout. Consider a waterproof membrane, especially if the laundry room is on an upper floor where a washing machine leak could damage the ceiling below.

Outdoor Areas

Use porcelain tile rated for exterior use (freeze-thaw resistant). Unglazed or textured porcelain provides the best traction when wet. Cement grout outdoors will crack — use a flexible polymer-modified grout or an exterior-rated epoxy.

Common Mistakes That Compromise Tile Waterproofing

• Skipping the waterproof membrane: Tile and grout alone are not waterproof. Always use a membrane in wet areas.
• Using drywall in showers: Standard drywall disintegrates when wet. Use cement board, foam board, or a waterproof panel system.
• Not sealing grout: Unsealed cement grout is a highway for water to reach the substrate.
• Improper slope: Shower floors must slope toward the drain. Flat or reverse-sloped floors pool water and accelerate grout failure.
• Ignoring corners and transitions: The junction between walls and floors, around fixtures, and at door thresholds are common leak points. Use waterproof tape or sealant at every transition.

Final Thoughts

Porcelain tiles are the most waterproof tile option available, but no tile installation is waterproof without proper grout management and a waterproofing membrane system. Whether you are tiling a shower, bathroom floor, or laundry room, thinking of waterproofing as a complete system rather than a single product will save you from costly water damage down the road.

Explore our full tile flooring guide and waterproof flooring guide for more help choosing the right materials for your project.