What Grout to Use in Shower: Complete Guide for Homeowners

A shower is the harshest environment tile ever faces: constant moisture, temperature swings, soap film, and standing water in the pan. Pick the wrong grout and you’ll be fighting mildew and crumbling joints within a couple of years. Figuring out what grout to use in shower walls and floors really comes down to two questions: how wide are your joints, and how much punishment will each area take. Answer those and the choice gets simple. Here’s how I spec grout on every shower I build.

The Three Types of Grout You’ll Consider

Every shower grout decision starts with three families of product. Each has a clear best use.

Unsanded (non-sanded) cement grout

Unsanded grout is a smooth cement-based grout meant for narrow joints, generally 1/16 inch up to about 1/8 inch. It’s the standard for shower walls tiled with subway tile, glass mosaics, or polished stone, where tight joints and a scratch-free finish matter. Because it has no sand, it won’t scuff delicate tile faces.

Sanded cement grout

Sanded grout adds fine sand for strength and shrink resistance in wider joints, roughly 1/8 inch and up. It’s the go-to for shower floors and any wall joint wider than 1/8 inch, because the sand keeps wide joints from cracking. The one caution: sanded grout can scratch soft, polished, or glass tile, so test in an inconspicuous spot first.

Epoxy grout

Epoxy grout, such as MAPEI Kerapoxy or Laticrete SpectraLOCK, swaps cement for a resin-and-hardener system. It’s essentially waterproof, stain-proof, and never needs sealing. That makes it the premium choice for wet, high-use showers, steam showers, and shower floors. The downsides are a higher price, a shorter working time, and a fussier installation, but for a demanding wet zone it’s the most durable option on the market.

Start With Joint Width

Before anything else, measure your grout joints. Width alone rules certain products in or out.

• 1/16 to 1/8 inch: Use unsanded cement grout or a fine epoxy. Sanded grout can be too coarse to pack cleanly into very tight joints.
• 1/8 inch and wider: Use sanded cement grout or epoxy. Unsanded grout shrinks and cracks in joints this wide.
• Mixed widths: Many showers pair 1/16-inch wall joints with 1/8-inch or wider floor joints, so it’s common to run unsanded on the walls and sanded or epoxy on the floor.

Manufacturers print joint-width ranges right on the bag. When in doubt, follow the label rather than a rule of thumb; a few products bridge the categories.

Then Factor In Water Exposure

Not every part of a shower gets equally wet, and that changes the recommendation. Wall areas above the spray line stay relatively dry, while the pan, curb, and lower walls take constant water. The wetter the zone, the more I lean toward epoxy or, at minimum, a high-performance sealed cement grout.

• Shower walls: Sealed unsanded or sanded cement grout works well and is the budget-friendly standard. Epoxy is an upgrade if you want zero maintenance.
• Shower floor and pan: This is the wettest spot. Epoxy is my first choice here for its waterproofing and stain resistance. If you use cement grout, seal it diligently.
• Steam showers: Go epoxy. The relentless moisture and heat overwhelm cement grout over time.
• Niches and benches: These pool water. Treat them like the floor and favor epoxy or well-sealed sanded grout.

Cement Grout vs. Epoxy: The Honest Comparison

Most shower decisions boil down to sealed cement grout versus epoxy. Here’s how they stack up.

• Waterproofing: Epoxy is inherently water-resistant; cement grout is porous and relies on sealer.
• Maintenance: Epoxy never needs sealing. Cement grout needs resealing every one to two years in a shower.
• Stain and mildew resistance: Epoxy resists both far better. Cement grout absorbs soap and body oils that feed mildew.
• Cost: Cement grout is cheap, a few dollars per pound. Epoxy runs significantly more, often $50 to $100-plus per unit, and installs slower.
• Installation: Cement is forgiving and DIY-friendly. Epoxy sets fast and demands quick, careful cleanup, so first-timers should work in small sections.

My short version: if the budget allows, epoxy on the shower floor is money well spent. On the walls, a quality sealed cement grout is perfectly reliable if you commit to resealing it.

Don’t Forget Sealing (For Cement Grout)

If you go with cement-based grout anywhere in the shower, sealing is not optional. Unsealed cement grout wicks water, breeds mildew, and stains. After the grout cures, usually 48 to 72 hours, apply a quality penetrating sealer such as MAPEI UltraCare or Aqua Mix Sealer’s Choice. Wipe on, let it soak, wipe off the excess, and add a second coat. Then reseal every one to two years in a shower, sooner on the floor. Epoxy grout skips this step entirely, which is a big part of its appeal.

Natural Stone Needs Extra Care

If your shower uses marble, travertine, or another natural stone, two rules apply. First, avoid sanded grout on polished stone, since the sand can scratch the surface; use unsanded or a non-scratching epoxy. Second, seal the stone itself before you grout, so grout haze doesn’t stain the porous surface. Stone showers reward patience: seal the tile, grout carefully, then seal the grout.

What About Silicone at the Changes of Plane?

One detail people miss: grout should not fill the inside corners where two walls meet or where the wall meets the floor. Those joints move slightly, and rigid grout cracks there. Instead, fill changes of plane with a matching 100% silicone caulk. Grout the flat field, then caulk the corners and the perimeter for a joint that flexes instead of failing.

Common Shower Grout Mistakes

After repairing plenty of other people’s showers, I see the same failures over and over. Avoiding these is half the battle.

• Skipping the sealer on cement grout. This is the number one cause of moldy, stained joints. If you use cement grout, budget for sealing on day one and every year or two after.
• Grouting the corners instead of caulking them. Rigid grout in a moving corner cracks, then water sneaks behind the tile. Use silicone at every change of plane.
• Using sanded grout on polished stone or glass. The sand scratches soft, glossy surfaces. Switch to unsanded or a smooth epoxy for those tiles.
• Rushing the cure. Cement grout needs 48 to 72 hours before it gets wet, and epoxy needs its full cure too. Showering too soon washes out uncured color and weakens joints.
• Over-washing during cleanup. Too much water on your sponge pulls pigment and cement out of the joint, leaving pale, weak, pinholed grout.

Cost and Budget Considerations

Grout is a small slice of a tile budget, so this is a poor place to cut corners. Cement-based sanded and unsanded grout runs roughly $15 to $25 for a large bag that grouts an entire shower, plus $20 to $40 for a bottle of penetrating sealer. Epoxy grout costs far more, often $50 to well over $100 per unit, and you may need more than one for a full enclosure. When you factor in that epoxy never needs resealing and resists the mold and staining that eventually force a cement-grout redo, the higher upfront price often pays for itself over the life of the shower. My usual compromise for cost-conscious clients: epoxy on the floor and lower walls where water pools, sealed cement grout up high where it stays drier.

A Quick Decision Framework

Put it all together and the choice falls out in three steps. First, measure your joints: 1/16 to 1/8 inch points you toward unsanded, wider than 1/8 inch toward sanded. Second, judge the water exposure: floors, pans, curbs, benches, and steam showers push you toward epoxy, while drier upper walls are fine with sealed cement grout. Third, check your tile: polished stone and glass rule out sanded grout. Run through those three and you’ll land on the right product almost every time.

The Bottom Line

Deciding what grout to use in shower spaces is really a two-part answer. Match the grout to your joint width first, unsanded for tight joints, sanded for wider ones, then let water exposure push you toward epoxy in the wettest zones like the floor and steam showers. Seal any cement grout religiously, caulk the corners with silicone, and give natural stone the extra protection it needs. Get those basics right and your shower will stay watertight and mildew-free for many years.