What Is Grout?

Grout is a cement- or epoxy-based material used to fill the joints between tiles after installation. Beyond looks, it locks tiles in place, keeps moisture and debris from getting underneath, and allows for small amounts of movement in the substrate below. Choosing the right type, and installing it correctly, has a real impact on how long your tile job lasts. This guide covers the main types of grout and how to choose between them. For quick definitions of related terms like sanded grout or grout haze, see our Tile Glossary.

Types of Grout

• Sanded Grout: Contains fine sand for added strength; best for joints 1/8 inch or wider, commonly used on floors.
• Unsanded Grout: A smoother formula for narrow joints (under 1/8 inch) and delicate polished surfaces that sand could scratch.
• Epoxy Grout: Made from epoxy resins rather than cement, highly resistant to stains and chemicals, popular for kitchens and commercial spaces.
• Pre-Mixed Grout: Ready-to-use grout, often polymer-modified for improved flexibility and stain resistance.

Sanded vs. Unsanded Grout: How to Choose

The general rule: joints 1/8 inch or narrower call for unsanded grout; wider joints need sanded grout, since the sand adds strength and reduces shrinkage. One exception, polished natural stone like polished marble usually calls for unsanded grout even at wider widths, since sand can scratch a polished surface during application.

Grout Color: More Than Just Aesthetics

Grout close in color to the tile creates a seamless look that can make a space feel larger. A contrasting color highlights the pattern, a great choice for layouts like herringbone or basketweave, but shows any inconsistency in tile placement more clearly. Darker grout also tends to hide dirt better on high-traffic floors.

Sealing Grout

Cement-based grout is porous and can absorb moisture and stains if left unsealed. A penetrating grout sealer, applied once the grout has cured (usually 48-72 hours), protects against staining and makes cleaning easier. Epoxy grout is largely non-porous and generally doesn't require sealing. See our Cleaning Blog for a full grout maintenance schedule.

Common Grout Problems

Cracking is often caused by an unstable substrate or skipped expansion joints where movement is expected. Staining usually comes from unsealed grout exposed to spills. Efflorescence, a white, powdery residue, is typically linked to excess water in the mix or moisture intrusion from below.

The Bottom Line

Grout is a small but critical part of every tile job, affecting both durability and finished appearance. See our Installation Blog for more step-by-step guidance, or browse the full Tile Glossary.