Grout is the material that fills the joints between tiles, and choosing the right type is more important than most people realize. The two main categories are sanded and unsanded grout, and using the wrong one leads to cracking, shrinking, or even scratching your tile. It is a simple decision once you know the rules, but getting it wrong creates problems that are expensive to fix.
What Is Sanded Grout?
Sanded grout contains fine sand particles mixed into the cement base. The sand acts as a filler and adds strength, making sanded grout resistant to cracking and shrinking in wider joints. It is the standard choice for floor tile and any application where the grout joints are wider than one-eighth of an inch. The sand gives the grout structural integrity in those wider gaps where unsanded grout would shrink and crack as it dries.
What Is Unsanded Grout?
Unsanded grout is a smooth, sand-free mixture that works best in narrow joints of one-eighth inch or less. Without the sand particles, it can be pressed into thin joints more easily and provides a smoother finish. Unsanded grout is the standard choice for wall tile with tight joints, rectified tile installations, and polished natural stone where sand particles could scratch the surface.
The Width Rule
Here is the critical rule: use sanded grout for joints wider than one-eighth inch and unsanded for joints one-eighth inch or narrower. The reason is physics. In a wide joint, unsanded grout shrinks too much as the water evaporates during curing, causing cracks. In a narrow joint, the sand particles in sanded grout are too large to pack tightly, resulting in a weak, porous joint.
Tile Material Considerations
Material matters too. Polished marble, polished granite, and glass tile should always use unsanded grout because the sand particles will scratch the polished surface during application. You cannot be careful enough to avoid this; the sand particles are everywhere in the grout and they will mark the surface as you work it into the joints and wipe the excess. Unsanded grout eliminates that risk.
Epoxy Grout: The Third Option
There is a third option worth knowing about: epoxy grout. It is waterproof, stain-proof, and does not need sealing. Epoxy grout works in any joint width and is ideal for showers, kitchen backsplashes, and anywhere that moisture and staining are concerns. The downsides are higher cost, a shorter working time during application, and a slightly different appearance. For most residential applications, cement-based sanded or unsanded grout does the job well.
Always Seal Your Grout
One last tip: no matter which grout you use, cement-based grout needs to be sealed after it cures. Grout sealer fills the pores in the cured grout and prevents moisture, stains, and mildew from penetrating the surface. Apply sealer after the grout has cured for 48 to 72 hours, and reapply annually in high-moisture areas like showers. At Adrian's Custom Services, we seal all grout as part of our tile installation because an unsealed grout joint is an unfinished job.