Unsanded grout, also called non-sanded grout, is made specifically for joints (i.e., the spaces between tiles) — smaller than 1/8-inch wide. Grout shrinks when it cures as the moisture evaporates from it, and unsanded grout shrinks significantly more than sanded grout. So it is unsuitable for wider grout lines.
Sanded grout has sand in it, which slows drying time and adds strength to the grout, but it can be difficult to use initially, and it is rough on hands.
Choosing the Right Grout for the Joint Size
Grout should be chosen according to the size of joint (space) between tiles. In most cases, experts recommend a wider joint, filled with sanded grout, as this tends to offer more strength than narrow joints with unsanded grout.
Joints 1/8" and wider must be filled with sanded grout, and joints less than 1/8" in width with unsanded grout. Users with an incredibly soft tile, such as marble, may feel compelled to use unsanded grout to avoid damaging the tile. In such cases, they must ensure the width of the tile joints is less than 1/8".
Unsanded grout, which is a mixture of Portland cement, powdered pigments, and water, has the consistency of a smooth pudding. Sanded grout is the same mixture, but with sand added in to give the grout tensile strength and to prevent shrinkage in tile joints. The added sand also gives sanded grout a rougher texture.
Both grouts can be used for wall and floor applications, with cement-based grouts traditionally used in residential work. Epoxy is a more recent addition to the market, but is much more expensive and is seldom required in residential installations. It is made of resin and hardener, and used in situations when tiles will be exposed to harsh elements, such as acids and greases from cooking.
Unsanded grout will generally dry very smoothly, as users are able to smooth out the grout with a little water during grout application. Sanded grout will always have a rougher texture. Epoxy grouts tend to dry with a plastic-smooth polish.
While older cement-based grouts were brittle and prone to cracking and drying with inconsistent coloration, today’s grouts use polymer additives to ensure color quality and flexibility.
Grout pigmentation is often neutral (e.g., beige or gray), though there are some deeper browns, light blues, and greens available. When choosing grout colors, one can opt for neutral colors that complement tile design, bolder colors that contrast with tiles (e.g., white grout with black tile), or colors that match or harmonize with the tile colors. Though unsealed cement-based grout can be stained or painted after it cures, it is a tedious process, so choosing the right color upfront is wise.
Unsanded grout typically dries lighter than sanded grout, and the water used to clean the grout may remove much of its pigmentation. The colors in sanded grout can also sometimes appear lighter than those seen in color charts after the grout has dried. However, sanded grout's pigments will usually dry into a color that is closer to a color chart's. It is recommended to choose a grout color slightly darker than the desired color, as very few people find their grout looks too dark after drying.
Sanded grout should not scratch most ceramic or glass tiles, and normal wiping with a damp sponge or rag shouldn’t provide enough force to cause damage. However, users may want to test application on porous and high-gloss tiles by rubbing a little dry grout or sand onto a loose tile. If sanded grout causes the tile damage, consider using unsanded grout in narrower joints.
Unpolished stone is porous and can be stained by grout, and so should be wiped with a grout sealer before grouting. All cement-based grouts are porous and subject to staining, so users must be careful during application and drying. Manufacturers often recommend sealing grout after it has cured for a few days and is completely dry.
Grout vs. Caulk
Grout is designed for water to pass in and out of the joint. It's like a 2-way street. Caulk, on the other hand, which is frequently composed of silicone, does not allow water to pass through.
Opinions vary on whether grout or caulk should be used in the joints where two planes meet (e.g., floor and wall, or wall corners). Using grout at the changes of plane has the advantage that it will match all the other grout lines. Grout also lasts slightly longer than caulking.
However, extra planning is required in advance if one wants to use grout this way. Space should be left for a grout line at changes of plane; tiles cannot be sticking to each other. Grout cannot flex, so the walls in a shower must not move even a little after installation, otherwise the grout will crack.
Caulk is flexible, so a little movement in the wall will not cause it to crack. Caulk can also be used in instances where tiles are butting up against each other. It can stick to the surface of tiles and provide necessary adhesion.
Don't Replace Grout with Caulk
Over time, it is natural for some house settlement and foot traffic to cause minor cracks in grout. In such cases, fresh grout — not caulk — should be used to seal the cracks. When caulk is used over grout, it can seal in moisture, resulting in the growth of mold. See this video for more detail on how caulk traps moisture.
Most grout jobs, whether of the sanded or unsanded variety, will last for 10-15 years. Much of grout's durability comes down to other related factors, however, such as whether the right grout has been used, whether it was originally allowed to cure and was protected with a sealant, and whether the tiles and grout are in a high traffic area, such as a main bathroom. Whenever there are numerous cracks or pits, or signs of mold or mildew, partial re-grouting or a complete replacement of grout may be required.
Grout will form cracks if not mixed properly. Using the right type of grout — sanded or unsanded — is also very important for preventing cracks.
If the incorrect amount of water has been mixed with the grout powder, and the mixture is too thin, holes will form in the grout as it dries, which can cause cracking. Cracking will occur whenever users don’t fill joints completely. Unsanded grout shrinks more than sanded grout, and so when it is used in joints too large, it will crack. This happens within 28 days of the grout installation, the time it takes for grout to fully cure.
In some cases, grout will crack because of movement in a joint, often at the corners, or where different materials are joined. In such cases, users should consider caulking the joints instead. Caulk is a flexible substance (silicone-, acrylic-, or latex-based) that closes up joints, providing thermal insulation and control over water penetration.
Grout can discolor during application and over time. There are several reasons grout can become discolored during application:
- There is too much water in the grout mixture.
- The grout is not allowed to dry completely before cleaning.
- Joints are not thoroughly filled.
- Dirty tools are used for application.
- People walk on the tiles before the grout is completely dry.
Discoloration over time occurs primarily when grout is not sealed. This leaves the grout exposed to water and dust, and the grout will inevitably take on the colors of that which it is exposed.
Various grout cleaning products are available to help restore color, and grout stains which permanently alter the color of the grout can also be used to correct discolorations. Epoxy-based stains provide the added benefit that users won’t need to reseal their grout in the future, as the epoxy formula provides a tough, long-lasting seal.
Repairs and Maintenance
Harsh, acidic cleaners should be avoided, as should the use of steam cleaners on tile. Using either may damage grout and/or tile and will likely lower the life expectancy of the grout and its sealant. Look for cleaners that are made especially for grout.
Replacing Old Grout
Old, stained grout can often be renewed, though in extreme cases one may have to regrout or even retile. A degreasing agent with a stiff-bristle brush will generally clean old grout well, but some spot regrouting will probably be necessary. Spot regrouting involves digging out cracked or crumbling areas and replacing them with new grout, as per the grouting methods detailed above. Using a grout colorant to paint the grout can also be used to make old grout look new again.
Sanded grout costs less than unsanded grout, predominantly because the sand used in sanded grout is cheap and so lowers the cost of production. The cost per pound of unsanded grout ranges from approximately $1.99 to $6.99, depending on brand and quantity purchased. The cost per pound of sanded grout ranges from approximately $0.50 to $4.00. Unsanded grout is available in smaller quantities than sanded grout, and both are available in a range of colors.
How to Apply Grout
Grouting is done the same way for floor tiles, wall tiles, ceramic tiles, porcelain tiles, and so on.
- Lay the tiles. Initial laying of the tiles plays an important role in grouting. While grouting is a job most users will be able to accomplish, tile-laying is generally best left to professionals.
- Choose the right grout for the joint size.: Joints 1/8-inch and wider must be filled with sanded grout, and joints less than 1/8-inch in width with unsanded grout.
- Mix grout. Users will need two buckets for grouting tiles: one for mixing grout and another for rinsing sponges. A trowel can be used for mixing the grout, and grout floats, sponges, and cloths are used to apply it. Some experts have suggested using a piping bag for filling joints with grout, but in practice this is often difficult.
- Use a sponge to spread grout onto the tiles. Using a sponge to scoop grout from the bucket, users should then spread it onto the tiles. A grout float or slightly damp sponge can then be used to push the grout around and into the joints. Ensure that the joints are completely filled, and scrape as much grout from the tiles as possible.
- Clean off excess grout from tiles. Once the grout is just hard enough, a clean, damp sponge can be used to wipe over the tiles and joints to clean off the surplus grout, without dragging any desired grout out from between the tiles. Repeat this process 3 times because although the tiles will look clean after the first wipe, residue forms on the surface again as they dry. Finally, a fine dust will be left on the surface of the tiles that can be wiped off with a dry cloth when the grout has completely dried.
- Allow the grout to dry. Manufacturers generally list drying times on their packaging, but users should allow more time in areas with high humidity. If the packaging doesn’t list drying times, it is best to wait as long as possible, but at least 24 hours. Keep in mind that it takes grout up to a month to fully cure.
- Seal the grout. After the grout has cured for a few days, users should apply a sealant to protect the grout's pigmentation and to prevent staining.
Mixing Ratio and Coverage
Pre-mixed grout, which contains a combination of grout and adhesive, is available, but grout powder gives a user more control, as it can be mixed to the desired consistency. Pre-mixed grout is firm and sticky and can be difficult to force into the joints.
Mixing powder grout can be easily done with a bucket and trowel. First add a little water to the bucket, and then add the powder – it is far more difficult to mix the grout if this is done the other way around. Each manufacturer will indicate how much water should be added on the bag of grout powder, typically 1.1 to 1.3 liters per 5kg of grout powder. Slowly add the grout powder to the water, stirring continuously until a creamy consistency like thick custard is reached. Make sure there aren’t any lumps as they can block a joint and stop it being filled properly.
The amount of grout required depends on the size of the tiled area being grouted, the length and width of the tiles, and the width and depth of the joints. All things equal, a user would require the same amount of sanded as unsanded grout. Most manufacturers provide details on the packaging to help a user calculate the amount they will require. There are also online tools, such as Bostik’s Grout Material Calculator and Mapei’s Product Calculator, to help calculate how much grout is needed.
- All About Grout - This Old House
- How Long Should Grout Set Up Before Walking on the Tile? - SF Gate
- Sealing Tile Grout: 2 Methods That Keep Your Grout Easy-To-Clean - About.com Home
- Should I Use Grout or Caulk? - Apartment Therapy
- What's Wrong With My Grout? Part 1: Discoloration - J3 Services
- Why is my Floor Grout Cracking? - The Floor Elf
- Grout - Sanded/Unsanded - Determining Which One to Use and Why - YouTube
- Wikipedia: Caulking