The short answer
Use unsanded grout for joints narrower than 1/8 in (about 3 mm) and sanded grout for joints 1/8 in and wider. Sand gives the grout body and strength in a wide joint. In a very narrow joint, sand grains cannot pack in, so smooth unsanded grout fills it better. Joints of exactly 1/8 in can often take either; read the product label for the joint range it is made for.
Side by side
| Unsanded grout | Sanded grout | |
|---|---|---|
| Typical joint width | Up to about 1/8 in (3 mm) | About 1/8 to 1/2 in (3–12 mm), per label |
| Texture | Smooth, creamy | Slightly gritty |
| Shrinkage and cracking in wide joints | Higher | Lower |
| Risk of scratching tile faces | Low | Higher on soft or polished surfaces |
| On vertical walls | Clings well, less sag | Fine in wider joints, can sag in narrow ones |
| Typical uses | Rectified tile, glass mosaic, polished stone, wall tile | Floors, natural-edge tile, wider joints |
When the rule bends
Scratch-sensitive tile
Polished marble, some glass tile and metallic or soft glazes can be scratched by the sand as you float and wipe. If the joints are wide enough to need sand, test on a spare tile first, or choose a grout that the tile maker approves for that surface. Many people switch to a premixed or epoxy grout for these cases.
Wall tile
Wall tile is usually set with tight joints, so unsanded grout is common there. Its smooth, sticky consistency also hangs on a vertical joint without slumping.
Wide or uneven joints
Handmade tile, slate and tumbled stone often need joints of 3/16 in or more. Use sanded grout, and check the maximum joint width on the bag.
Other grout types
- Epoxy grout is a two-part resin grout that resists stains and does not need sealing. It is harder to work with and sets fast, so practice first.
- Premixed (urethane or acrylic) grouts come ready to use in a tub and often cover a wide range of joint widths, with and without sand.
- High-performance cement grouts include polymers for better strength and stain resistance; some are rated for both narrow and wide joints.
Worked example: how much each job needs
The amount depends on joint size, not the grout type, though density varies a little between products. Using the grout calculator with 10 percent extra:
| Job | Tile and joint | Grout type | Grout needed |
|---|---|---|---|
| 30 sq ft subway backsplash | 3 × 6 in, 5/16 in thick, 1/16 in joints | Unsanded | About 2.9 lb |
| Same backsplash, wider joints | 3 × 6 in, 5/16 in thick, 1/8 in joints | Sanded | About 5.7 lb |
| 60 sq ft laundry room floor | 18 × 18 in, 3/8 in thick, 3/16 in joints | Sanded | About 4.6 lb |
Doubling the joint width doubles the grout, which is why the backsplash jumps from about 2.9 to 5.7 lb. Large tiles have far fewer joints per square foot, so the laundry floor, twice the area of the backsplash and with wider joints, still needs less grout than the wide-joint backsplash. A 10 lb bag is enough for any of these three jobs on its own.
Choosing a color
Grout color changes the look of a tile job as much as the tile. A grout that matches the tile makes joints fade away and hides small layout errors; a contrasting grout outlines every tile and shows every uneven line. Light grout on a floor shows dirt sooner. Look at the dry color samples at the store against a real tile, because grout often dries lighter than it looks when wet.
Replacing old grout
When regrouting, remove the old grout to at least half the joint depth with a grout saw or an oscillating tool fitted with a grout blade, vacuum the joints, and match the new grout to the joint width as above. Go slowly near glazed edges; a slip chips the tile.
Sealing and care
Both sanded and unsanded cement grouts are porous. Neither is waterproof; the waterproofing in a shower comes from the membrane behind the tile. Many cement grouts benefit from a penetrating sealer once fully cured, often after a couple of days, but follow the grout maker's timing. Epoxy grout does not need sealing.
Tips for a clean result
- Mix to the consistency on the bag. Extra water weakens grout and causes color variation.
- Press the grout fully into the joints with a rubber float held at an angle, then strike off the excess diagonally across the tiles.
- Wipe with a barely damp sponge. Too much water pulls cement out of the joints.
- Use flexible sealant, not grout, where tile meets a tub, at inside corners and at perimeter joints.
- Wear gloves: cement grout is alkaline and can burn skin.
Frequently asked questions
Can I use sanded grout for 1/16 inch joints?
Usually not. Sand grains do not pack into joints that narrow, so the joint is left weak and patchy. Use unsanded grout or a product rated for narrow joints.
Is unsanded grout waterproof?
No. Neither sanded nor unsanded cement grout is waterproof. Sealing slows staining, but water protection in a shower comes from the membrane behind the tile.
Does sanded grout need more grout than unsanded?
The amount depends on the joint volume, not the type. A 30 sq ft backsplash of 3 × 6 in tile needs about 2.9 lb with 1/16 in joints and about 5.7 lb with 1/8 in joints.
Do the math for your own project.
Open the grout calculator