Sanded vs Unsanded Grout: Joint Width, Surfaces and Which to Use

Use unsanded grout for joints narrower than 1/8 inch and sanded grout for joints 1/8 inch and wider (most sanded products are rated up to about 1/2 inch). Joint width settles most decisions. The exception is surface: polished marble, glass and high-gloss glazes can scratch under sanded grout, so they push you toward unsanded or a non-abrasive alternative.

What actually differs between the two

Both are cement grouts. Each starts with portland cement, pigments and usually some dry polymer, and both cure by hydration when you add water. The difference is the aggregate. Sanded grout carries a graded silica sand that can make up a large share of the dry mix. Unsanded grout leaves the sand out and relies on very fine fillers (ground limestone or similar) plus a higher polymer content for adhesion and workability. For the chemistry in more depth, see what grout is made of.

That one change in aggregate drives everything else. Cement paste shrinks as it cures and loses water. Sand grains don't shrink, so a well-graded sand skeleton holds the joint dimensionally stable and resists compression and abrasion. Take the sand away and the joint is mostly paste. In a narrow joint that's fine, because the tile edges are close together and the volume of paste is small. In a wide joint the paste shrinks more than the joint can tolerate, and you get hairline cracks down the center or a gap along one tile edge.

Side-by-side comparison

Notice that the standards row is the same for both. ANSI A118.6 and A118.7 don't define "sanded" or "unsanded". They set performance criteria (strength, shrinkage, water absorption, color consistency for A118.7). A sanded product and an unsanded product from the same line may both meet A118.7. The sand/no-sand choice is about joint geometry and surface, not about passing a standard. More on the standards in ANSI and ISO grout standards explained.

The joint width rule and why it works

The 1/8 inch dividing line is a rule of thumb that most manufacturers' data sheets agree with, give or take. It works from both directions.

Why unsanded fails in wide joints

A 3/16 inch floor joint filled with unsanded grout often looks fine on day one. Over the next week, as it dries, the paste shrinks. Because it's bonded to both tile edges, it either cracks down the middle or debonds from the weaker side. Under foot traffic, the soft paste also wears faster and starts to dish below the tile surface. If you're looking at cracked grout in a wide joint, wrong grout type is one of the first things to check.

Why sanded fails in tight joints

In a 1/16 inch joint, the larger sand grains can't pass into the gap. The float drags them across the top, so paste goes in but the sand stays near the surface, or the grout bridges the joint with a hollow below. That shows up later as pinholes and voids, or as grout that sounds hollow and crumbles when you scratch it. It also makes cleanup harder, since loose sand smears across the face.

Surface scratch risk: the second deciding factor

Sand is quartz, which is harder than calcite (the main mineral in marble, limestone and travertine) and harder than most glass. When you float sanded grout diagonally and then sponge and buff, those grains get pushed across the tile face. On honed stone or matte porcelain you won't see anything. On these surfaces you might:

• Polished marble, polished limestone and polished travertine
• Glass tile, including glass mosaic sheets
• Metallic, mirrored and some high-gloss glazed ceramic
• Soft glazes on handmade tile and some zellige

If the joint is narrow, the answer is simple: use unsanded. The trouble comes when a scratch-sensitive tile has a wide joint, such as a polished marble floor at 3/16 inch or a handmade tile with irregular 1/4 inch gaps. Unsanded will crack and sanded may scratch. That's where you look past both: epoxy grout, many premixed grouts, or a high-performance cement grout with a fine aggregate that the manufacturer specifically lists as safe for the surface. See grout for natural stone and grout for glass tile for those specific cases.

Handling, cleanup and finished look

Unsanded grout is creamy and sticky. It clings to vertical surfaces and is easy to pack into narrow joints with a soft rubber float. That stickiness also means it can be harder to clean off textured or porous tile faces, and it's more prone to haze if you let it set too long before sponging. Sanded grout feels stiffer and grittier, which makes it easier to tool firmly in wide joints and less likely to slump out of floor joints. On walls, mix sanded grout on the stiff side of the TDS water range so it doesn't sag.

The finished texture differs. Unsanded joints look smooth and slightly glossy when tooled. Sanded joints have a fine grain you can feel. On a contemporary wall with tight rectified joints, smooth unsanded looks crisp. On a rustic floor, sanded texture reads as natural. Grout color appears slightly different between the two even with the same color name, because sand dilutes pigment and changes how light scatters. Check samples of the exact type you'll use. The grout color guide covers this in more detail.

Strength, durability and maintenance

In the joint widths each is designed for, both perform well. Sanded grout generally has higher compressive strength and better abrasion resistance, which is why it's the default for floors. Unsanded grout in a narrow joint is protected by the tile edges on both sides and sees little direct wear, so its lower abrasion resistance rarely matters on walls and backsplashes.

Both are porous cement products. Basic A118.6 grouts absorb more water than A118.7 high-performance grouts, and a penetrating sealer helps both resist staining in kitchens, showers and entry floors. Read do you need to seal grout for which situations justify it. Neither type is waterproof. In a shower, the waterproofing is the membrane behind the tile, not the grout.

The blurred middle: fine-aggregate and high-performance grouts

The neat sanded/unsanded split comes from traditional bagged grouts. Many current high-performance cement grouts use a fine, graded aggregate and enough polymer to cover a wide joint range in a single product, often from about 1/16 inch up to 1/2 inch or more. They are technically "sanded" because they contain aggregate, but the particles are fine enough to fill narrow joints and are often described by the maker as suitable for a wider range of surfaces. Whether a given product is safe on polished marble or glass is a claim only the manufacturer can make. Read the "surfaces" or "limitations" section of the TDS and still do a test on a spare tile.

Premixed and epoxy grouts sidestep the question differently. Most use fine fillers and resin binders, and many are rated for joints from about 1/16 inch to 1/2 inch. Compare them in epoxy vs cement grout and premixed vs powder grout.

Which should you choose?

Work through these in order. The first one that applies decides.

1. Joint under 1/8 inch, any surface: unsanded, or a fine-aggregate grout whose TDS lists that width.
2. Joint 1/8 inch or wider on porcelain, ceramic, honed or tumbled stone, quarry or brick: sanded.
3. Joint 1/8 inch or wider on polished marble, glass, metallic or high-gloss glaze: neither plain option is ideal. Use a non-abrasive epoxy or premixed grout, or a fine-aggregate grout that the manufacturer approves for that surface, after a test.
4. Mixed joint widths on one surface: one product whose range covers all of them.
5. Heavy traffic, commercial kitchen, or a shower you don't want to seal: look beyond both at epoxy or urethane. The grout type selector can help narrow it down.

Once you know the type, use the grout calculator to estimate quantity. Wider joints use a lot more grout than people expect.