Bathroom Grout: Floors, Walls, Tub Surrounds and Where to Caulk Instead

Most bathroom tile does well with a high-performance cement grout (ANSI A118.7) or an epoxy grout on the floor and tub surround, and a high-performance or standard cement grout on dry walls. The bigger decision is where not to grout: the tub-to-tile joint, inside corners, floor perimeter, vanity top and toilet base get flexible sealant.

Walk-in showers are covered in the shower grout guide and the shower floor guide. This page handles the rest of the bathroom.

Bathroom grout by zone

Bathroom floors

Bathroom floors look like ordinary floors but carry more water. Bath mats hold it against the grout, toilets occasionally overflow, children splash, and the floor gets mopped often. The area in front of the toilet also gets urine, which is acidic when fresh and turns alkaline and smelly as it breaks down, and both stages stain porous grout.

For most homes, a high-performance cement grout is a good fit: it absorbs less than standard grout, holds color better and resists stains when sealed. Epoxy is the low-maintenance upgrade, worth choosing for light grout colors, households with small children, or anyone who does not want to reseal. The floor grout guide covers floors in general; the points below are bathroom-specific.

• Joint width: With rectified porcelain, 1/16 to 1/8 inch joints are common; with calibrated or handmade tile, wider. ANSI A108.02 guidance ties minimum joint width to tile size variation. See the joint width guide.
• Perimeter gap: Leave a gap at walls and the tub (commonly 1/4 inch, hidden by baseboard or filled with sealant). Grouting tile tight to walls is a classic cause of tenting and cracked grout lines along a wall.
• Heated floors: Radiant heat speeds curing and adds thermal movement. Leave the heat off while grout cures and follow grouting radiant heated floors.
• Color: Mid-tone grout hides foot traffic soil and hair. Bright white cement grout on a bathroom floor needs either epoxy or diligent sealing.

Grout around toilets

The tile around a toilet is grouted like the rest of the floor. The toilet itself sits on a wax ring or foam seal over the closet flange, and its base sits on top of the finished tile. Two questions come up constantly.

Grout or caulk at the toilet base?

Never grout the toilet base to the tile. Grout cracks when the toilet flexes and is impossible to remove cleanly when the toilet needs to come up. Many plumbing codes require the base of a floor-mounted toilet to be sealed to the floor with caulk, which also keeps mop water and urine from getting under the base. A common practice is to caulk the front and sides and leave a short gap of an inch or two at the back, so a leaking wax ring shows up as water on the floor instead of rotting the subfloor unseen. Local code and inspectors vary on that point, so check what applies.

Tile around the flange

The flange should be set so its top sits on, or slightly above, the finished tile surface. Tile cut around the flange should finish close to it without trapping grout against the flange, and the cut edges are hidden by the toilet base. Grout in this area must be fully cured before the toilet goes back on, because the wax ring and bolts load the surrounding tile.

Tub surrounds

A tiled tub surround takes direct shower spray on the lower walls and steam above. Grout here behaves like shower wall grout, and the same principle applies: grout is not waterproofing. The wall behind it needs cement board with a membrane, a waterproofed foam board, or another assembly the tile industry recognizes for wet areas. See does grout waterproof tile.

Wall joints in a tub surround are often 1/16 to 1/8 inch with subway or rectangular tile. Unsanded or fine high-performance grout suits joints under 1/8 inch; sanded or high-performance grout suits 1/8 inch and wider (see sanded vs unsanded grout). Wall grouting technique differs from floors: smaller batches, stiffer mix, and working from the top down. See grouting walls vs floors.

The tub-to-tile joint

This is the most failure-prone joint in any bathroom. A tub is a separate fixture that flexes and drops slightly when it fills with water and a person. Grout in this joint cracks within months and lets water run behind the tile onto the tub flange and the wall below.

1. Leave the gap. When setting the bottom row of wall tile, hold it about 1/8 to 1/4 inch above the tub rim. Do not grout this joint.
2. Fill the tub. Before caulking, fill the tub with water so it settles to its loaded position. This prevents the sealant from being stretched every time the tub fills.
3. Clean and dry the joint. Remove dust, grout and soap residue. Joint surfaces must be dry for silicone to bond.
4. Apply sealant. Use a 100 percent silicone or a sealant rated for tub and tile in a matching color, and tool it into a smooth concave bead.
5. Let it cure before draining. Leave the water in until the sealant skins over and cures per its label, then drain the tub.

The same rule applies to the vertical inside corners of the surround and the wall-to-ceiling joint if the ceiling is tiled. Those joints move, and grout in them cracks.

Tub decks and aprons

Tile decks around drop-in tubs hold puddles and shampoo bottles, and the joint between the deck and the tub rim takes constant water. Slope the deck slightly toward the tub where possible, use epoxy or sealed high-performance grout on the deck, and use sealant at the rim. Tiled aprons on the tub front need an access panel to the drain and overflow, and that panel's perimeter should be sealant or a removable trim, not grout.

Vanity backsplashes and tiled vanity tops

A vanity backsplash gets splashes, toothpaste, makeup and hair products. It sees far less water than a tub surround but more staining agents than most walls. A high-performance cement grout, a stain-resistant premixed grout, or epoxy all work. For light colors near a busy sink, the stain-resistant grout guide is worth a look.

The joint where the backsplash meets the countertop gets sealant, not grout. Stone, quartz and laminate tops all move differently from the wall, and grout in that joint cracks. The same goes for the ends where the backsplash meets a side wall.

Tiled vanity tops (less common now than in earlier decades) behave like a small countertop. They see standing water, hair dye, nail polish remover and cosmetics. Epoxy grout is the practical choice. See the countertop grout guide for the joint layout and edge details.

Choosing one grout for the whole bathroom

Many homeowners want one product and one color for every tiled surface. That is reasonable as long as the product suits the wettest surface in the room. A high-performance cement grout or an epoxy works on floors, tub surrounds and backsplashes alike. A standard sanded cement grout used everywhere will look fine on day one but needs more sealing and cleaning on the floor and surround.

If the choice is still unclear, the which grout do I need guide narrows it down by tile and location.

Ventilation, sealing and care

Bathroom grout that grows mildew is usually responding to humidity, not to its own weakness. A properly sized exhaust fan run during and for 15 to 20 minutes after bathing keeps walls and grout dry enough that mildew struggles to take hold. See grout mold and mildew.

• Seal cement grout after it cures, then test it yearly near the tub and in front of the toilet with a water drop test. See do you need to seal grout for the decision.
• Clean floors with a pH-neutral tile cleaner. Bleach-based bathroom sprays used often can lighten colored cement grout over time.
• Replace the tub sealant when it shows mildew under the surface or pulls away. Silicone in a bathroom typically lasts several years, not decades.
• Persistent smell near the toilet usually comes from urine in porous grout or a failing wax ring, not mildew. See urine on grout and smelly grout.