What Tile Holds Up in a Shower
Most people pick the shower tile by looking at it. That is backwards. The tile is the part of a shower that is easiest to replace. The pan, the membrane and the slope are the parts that decide whether the shower works, and the tile has to fit what they do.
The Short Answer
In a Shower, the Substrate Matters More Than the Tile
A beautiful tile on a floor with no slope and a pan that has no waterproofing under it is a shower that fails. A plain tile on a properly built shower holds up for years. So the order of decisions matters: the pan and the waterproofing come first, then the substrate, and the tile gets picked to suit both.
Three Things to Check on Any Tile
There are three things to check on any tile before it goes into a shower, and none of them is the color. How much water it takes on, how it behaves underfoot when it is wet, and how big it is.
Porcelain, Ceramic, or Stone
Water Absorption Is the Number That Separates Them
Tile is classified by how much water its body takes on. The four groups below are the ISO 13006 groups. ANSI A137.1, the standard used in the United States, draws its bands in slightly different places. Porcelain is fully vitrified, which means it absorbs 0.5 percent or less. That is why it holds up outdoors, in freezing weather and in a wet room.
- Porcelain, group BIa, absorbs 0.5 percent or less. Dense, hard, and the usual right answer for a shower floor and wall.
- Vitreous ceramic, group BIb, absorbs between 0.5 and 3 percent. A reasonable wall tile, and fine on a wall that does not get soaked.
- Semi-vitreous ceramic, group BIIa, absorbs between 3 and 6 percent. It has a place in a dry room, and it is not a shower floor.
- Wall tile, group BIII, absorbs more than 10 percent. It is made for a vertical surface and it is not made for a shower floor.
Read the Absorption Figure on the Box
One honest warning. In ordinary trade use the word porcelain is not controlled. Some factories market higher absorption tile under that name. So read the absorption figure on the box rather than trusting the label on the front of the sample board.
Slip Resistance
Slip Resistance Is a Number, and It Is on the Box
The test is the dynamic coefficient of friction, or DCOF, measured under ANSI A326.3, the standard the Tile Council of North America publishes. For a level interior floor that gets walked on when it is wet, the threshold is a wet DCOF of 0.42 or higher.
A few things worth knowing before you pick a tile in a showroom.
- The number is for the finish, not the color. The same pattern in a polished finish and a matte or textured finish can test differently. Ask for the number on the exact finish.
- The standard sorts tile into product use groups: interior dry, interior wet, interior wet plus, exterior wet, and oils and greases. Ask which group the tile belongs to.
- The standard does not set a separate number for a shower floor. On a sloped, wet floor the texture of the surface and the manufacturer's own statement carry more weight.
- An older spec sheet may quote 0.60. That is a static friction test from an older standard. It is not the same measurement and the two are not interchangeable.
- No floor tile is slip proof. A number tells you how a surface behaves under a test.
What the Shower Needs More Than the Tile Does
The Pan, the Membrane, and the Slope
A shower floor is not a flat floor. It slopes toward the drain so the water leaves. That slope is set before any tile is picked, and it decides what the tile has to do.
The Layers Behind the Tile
Under the tile there is a pan that catches the water and carries it to the drain, a waterproofing membrane over it, and backer board with its own membrane and sealed seams on the walls. That assembly is flood tested before a single tile goes on. Our guide to what goes behind shower tile goes into the layer stack in detail.
Build First, Then Choose the Tile
So the order is this. The pan gets built and flooded and tested. The wall gets its membrane. Then the tile gets chosen to suit the surface that exists. A tile that is stiff and flat wants a flatter substrate, and a mosaic on a backer board wants less. The tile that gets picked first and the floor that gets built to match is the way to do it.
What Goes Wrong
The Four Ways a Shower Tile Job Goes Wrong
- A flat shower floor. Water needs somewhere to go. If the floor does not slope to the drain, water sits, and standing water is what finds the weak spot in the assembly.
- Grout where sealant belongs. The corner where the wall meets the pan, and the joint around the drain, take flexible sealant. Cement grout in a joint that moves cracks, and water follows the crack in.
- Unsealed cement grout on a shower floor. It is porous by design, it takes on water, and it darkens and stains. Sealing it helps, and it is not the same as it not absorbing.
- A polished or honed stone floor on a slope. It can test below the wet threshold, and stone in a shower also has to be sealed and resealed on a schedule.
Big tile adds one more failure mode. Tile with an edge of 15 inches or more, which is where the flatness tolerance tightens, needs a substrate flat to a tolerance of about an eighth of an inch in 10 feet, measured from the high points, with no more than a sixteenth of an inch in 2 feet. Put that tile on a floor that does not meet it and you get lippage, which is a height difference between two tiles that you feel underfoot and see under raking light. The subfloor article covers how that is measured.
At the Showroom
What to Bring With You
- A tape measure, or the width and depth of the shower. Tile that fits the space well has fewer cuts, and fewer cuts means fewer pieces that can differ from each other.
- The wet DCOF number for the finish you are standing in front of, written down. Ask for it in writing on the spec sheet.
- The water absorption figure from the box. That tells you what the tile body is made of, and it is the figure that matters, not the name on the display.
- A photo of the shower, if you already have one. Where the drain sits and where the walls are decides the layout more than the pattern does.
- The grout sample. Grout is chosen in the same trip as the tile, not a week later, because the color of the joint and the color of the tile have to be looked at together.
What to Do Next
Have the Shower Opened Before the Tile Is Ordered
If you are building a new shower, decide the pan and the substrate before you pick the tile. If you are replacing tile in an existing shower, the useful question is what is under the tile right now. We open it and look, and we tell you whether the shower needs a retile onto a sound substrate or whether the pan has to come out.
What the Estimate Puts in Writing
On the estimate we write down what we find, what it means for the tile you can use, and what the work involves. If the shower is in good shape, we will say that too.
Frequently Asked Questions
Tile for a Shower - Questions
Porcelain is the safest default because it absorbs so little water and does not chip easily. It is not the only good answer. The deciding factors are the wet slip rating, the size of the tile, and what the floor and walls are built on, and those matter more than the material name.
Look for a wet DCOF of 0.42 or higher, measured under ANSI A326.3. That is the minimum for a level interior floor that gets walked on wet. On a shower floor the standard sets no separate number, so the texture of the surface and the manufacturer's own product use statement carry more weight there.
Grout goes in the joints between tiles on the floor and on the wall. The change of plane, the corner where the wall meets the pan, and the joint around the drain get flexible sealant instead. Cement grout in a shower joint is a crack waiting to happen, and it lets water behind the tile.
It depends on the stone and on the room. Stone needs sealing, some stones need more care than a busy shower can give them, and a honed or polished stone floor often tests below the wet slip threshold. Ask for the wet DCOF of the exact finish before you commit to it.
It does. Small tiles, and mosaic sheets, follow the shape of the floor and hide small irregularities. Tile with an edge of 15 inches or more needs a much flatter substrate and a careful layout, because it does not bend to fit what is under it.
Still have questions? Call us at (860) 990-2332
Where this work gets done
Shower tile installation, Large format tile installation by Dmtilellc across Connecticut. Ask for a free estimate.
Let Us Open the Shower and Show You What You Are Working With.
If you are in New Britain, Berlin, Newington, Plainville, Farmington, Avon or a nearby Connecticut town and need tile installation, bathroom remodeling, shower waterproofing, backsplash work, or floor tile installation, contact Dmtilellc today. Free estimates available.