Grout Glossary

Updated October 3, 2026

This glossary defines the terms tile setters, data sheets and standards use when they talk about grout, from ANSI A118.7 and ISO CG2WA to slaking, haze, lippage and L/360. Each definition is short and precise, and each links to the Grout Atlas guide that covers the topic in depth. Jump to a letter below.

A

A (ISO class): The ISO 13007-3 suffix for high abrasion resistance in an improved cementitious grout, as in CG2A or CG2WA. It indicates the grout lost less material in the standard abrasion test than a basic grout, which matters on busy floors and in commercial entries. See how the suffixes combine in grout standards explained.
Absorption: The amount of water a tile body or a cured grout takes up, expressed as a percentage of dry weight. ANSI A137.1 classifies porcelain tile as 0.5 percent absorption or less, while grout absorption is limited by ANSI A118.7 and the ISO W class. Highly absorbent tile edges can pull water from fresh grout and cause shading, as covered in grout discoloration and shading.
Acid cleaner: A cleaner with a low pH (roughly 1 to 4) that dissolves mineral deposits such as cement haze, hard water scale and efflorescence. Acids also attack cement grout itself and etch calcareous stone, so they are used sparingly, diluted, on a pre-wetted surface and rinsed thoroughly. The grout cleaners by pH guide covers when an acid is the right choice.
Aggregate: The inert granular filler in grout, usually graded silica sand in sanded grout and very fine fillers in unsanded grout. Aggregate gives the joint bulk, controls shrinkage and adds compressive strength and wear resistance. Its role in the mix is explained in what grout is made of.
Alkaline cleaner: A cleaner with a high pH (roughly 9 to 12 or more) that breaks down grease, body oils, soap residue and some organic stains. Strong alkaline cleaners are the usual tool for degreasing kitchen floors and stripping some topical sealers. They are generally safe on cement grout and stone but can dull certain finishes, so test first; see grout cleaners by pH.
ANSI A108.10: The American National Standard for installation of grout in tilework. It covers joint preparation, filling joints fully, cleaning, and curing practices that installers are expected to follow regardless of grout type. Its place among the other grout standards is covered in grout standards explained.
ANSI A118.3: The American National Standard for chemical-resistant, water-cleanable tile-setting and grouting epoxy. Grouts meeting it are 100 percent solids reaction resin systems with high bond strength, low absorption and good chemical resistance. Product details are in the epoxy grout guide.
ANSI A118.6: The American National Standard for standard cement grouts for tile installation. It sets baseline requirements for traditional sanded and unsanded portland cement grouts, which may or may not contain polymer. See grout standards explained for how it differs from A118.7.
ANSI A118.7: The American National Standard for high-performance cement grouts. These polymer-modified grouts must meet tighter limits on shrinkage and water absorption and show better color consistency than A118.6 grouts. Many urethane and single-component premixed grouts are evaluated against A118.7 criteria when the manufacturer claims it; see high-performance cement grout.
ANSI A118.8: The American National Standard for modified epoxy emulsion mortar and grout. These products combine epoxy resin and hardener with portland cement and sand, giving better stain and chemical resistance than cement grout but less than a true A118.3 epoxy. They are less common today; see specialty grouts.
ANSI A137.1: The American National Standard specification for ceramic tile, which defines tile types, dimensional tolerances and properties such as water absorption. It is the standard that defines porcelain tile as having 0.5 percent absorption or less. That matters for grout selection, as discussed in grout for porcelain tile.

B

Back-buttering: Spreading a thin, flat coat of thinset on the back of a tile before setting it into the troweled bed. It improves mortar coverage, which reduces hollow spots and cracked tile and helps keep joints from cracking later. It is standard practice for large-format and natural stone tile; see why grout cracks.
Bucket: In grouting, usually two or three clean pails: one for mixing, one or two for clean rinse water during sponging. Using a separate rinse bucket and changing the water often is one of the simplest ways to reduce haze and shading. Setters often mark buckets with water lines so every batch gets the same water dose; see grout tools.

C

Calcareous stone: Natural stone composed mainly of calcium carbonate, such as marble, limestone, travertine and onyx. It is acid sensitive: acidic cleaners, sulfamic acid, vinegar and many grout haze removers will etch it. Grout and cleaner choices for these stones are covered in grout for natural stone.
Calcium hydroxide: A byproduct of portland cement hydration, also called portlandite, that sits in the pores of cured cement grout. When water carries it to the surface it reacts with carbon dioxide in air to form calcium carbonate, the white bloom known as efflorescence. See efflorescence on grout.
Carbide grout saw: A hand tool with a blade coated in tungsten carbide grit, used to cut old grout out of joints. It is slow but controllable, which makes it the safest choice next to soft-glazed or easily chipped tile. Technique is covered in how to remove grout.
Caulk: The common name for a flexible sealant used to fill joints that must move, such as changes of plane, perimeters and joints at tubs and countertops. Grout is rigid and cracks in those locations, which is why TCNA EJ171 calls for sealant there. Color-matched sanded and unsanded caulks are sold to sit next to grout; see caulk vs grout for movement joints.
Cement grout: Any grout based on portland cement, mixed with water (or a liquid additive) and cured by hydration. It includes standard sanded and unsanded grouts under ANSI A118.6 and polymer-modified high-performance grouts under A118.7. Compare it with resin systems in epoxy vs cement grout.
CG1: The ISO 13007-3 class for normal cementitious grout. It meets basic requirements for strength, shrinkage and water absorption with no added performance claims. See grout standards explained.
CG2: The ISO 13007-3 class for improved cementitious grout, which meets the CG1 requirements plus at least one additional characteristic. The suffix tells you which: W for reduced water absorption, A for high abrasion resistance, and F can be added for fast setting, as in CG2WAF. Details are in grout standards explained.
Change of plane: Any place where tile turns a corner or meets another surface at an angle, such as inside wall corners and the joint where a wall meets the floor or tub. These joints move differently on each side, so TCNA EJ171 calls for flexible sealant instead of grout. See caulk vs grout for movement joints.
Chemical resistance: The ability of cured grout to withstand acids, alkalis, fats, sugars and cleaning chemicals without softening, eroding or staining. Cement grout has limited acid resistance, while epoxy and furan grouts are formulated for it. Commercial kitchens and labs need this property; see specialty grouts.
Colorant: An opaque, pigmented coating applied over existing cement grout to restore or change its color and seal it at the same time. Colorants are film-forming, so the grout must be clean, dry and free of sealer for them to bond. Application and durability are covered in grout colorant.
Coverage: The tile area one bag or bucket of grout will fill, which depends on tile size, tile thickness and joint width. Small tiles and wide joints use far more grout per square foot than large tiles with narrow joints. Estimate yours with the grout calculator.
Cure: The process by which grout gains strength after it sets: hydration for cement grout, chemical reaction for epoxy, and drying or reaction for urethane and premixed grouts. Cement grout keeps hardening for weeks, but most products allow light foot traffic after about 24 hours. Timelines by grout type are in grout cure time.

D

Damp curing: Keeping fresh cement grout slightly moist, often by light misting or covering, so it does not dry before hydration is well along. It can help in hot, dry or windy conditions, but many modern polymer-modified grouts are designed to cure without it, so follow the TDS. See grouting in hot and cold weather.
Deflection: How much a floor bends under load between its supports. Too much deflection is a leading cause of cracked grout and tile on wood-framed floors. It is expressed as a fraction of span, such as L/360 or L/720; see why grout cracks.
Dwell time: How long a cleaner, stripper or stain remover is left on the surface before agitating and rinsing. Too short and the product does little work; too long and it can dry on, or in the case of acids, damage the grout. Typical dwell times are covered in the grout stain removal guide.

E

Edge profile: A metal or PVC trim strip set into the thinset at tile edges, outside corners, transitions and terminations. It protects exposed tile edges and gives a clean finish where bullnose is not available. Some profile types are also made to serve as movement joints; see caulk vs grout for movement joints.
Efflorescence: A white, powdery or crusty deposit on grout, usually calcium carbonate formed when water carries calcium hydroxide to the surface. It points to water moving through the assembly, whether from early wetting, a wet substrate or an ongoing leak. Diagnosis and removal are in efflorescence on grout.
Epoxy grout: A two- or three-part reaction resin grout made of epoxy resin, hardener and filler, classed as ANSI A118.3 and ISO RG. It is highly stain and chemical resistant, has very low absorption and does not need sealing. It has a short working time and less forgiving cleanup; see epoxy grout.
Etching: Dull, lighter marks on calcareous stone caused by acid dissolving the calcite at the surface. Etching is surface damage, not a stain, so cleaners will not remove it; it needs polishing or honing. Avoiding it shapes cleaner choice on stone; see grout for natural stone.

F

F (ISO class): The ISO 13007-3 designation for fast-setting grout, added to a CG1 or CG2 class as in CG2F. Fast-setting grouts reach early strength quickly so the floor can return to service sooner, at the cost of a shorter working window. See specialty grouts for rapid-setting products.
Final set: The point at which a cement grout or mortar has fully stiffened and resists a set penetration test (measured in the lab by methods such as ASTM C191). After final set the material keeps gaining strength through cure but can no longer be reworked. See grout cure time.
Floating: Spreading grout across the tile and packing it into the joints with a rubber grout float held at roughly 45 degrees, working diagonally to the joints. A second pass with the float more upright scrapes off the excess. Full technique is in how to grout tile.
Furan grout: An industrial reaction resin grout based on furfuryl alcohol resin, used where strong acids, solvents and high temperatures are present, such as food processing and chemical plants. It requires specialist installation, often with a temporary wax coating on the tile. See specialty grouts.

G

Grout: The material that fills the joints between tiles, locking them in place, keeping debris out of the joints and giving the surface a finished look. Grout is not a waterproofing layer: water management depends on the membrane and substrate below. An overview of types is in the grout types hub.
Grout bag: A cone-shaped bag with a nozzle, similar to a pastry bag, used to pipe grout into joints. It is useful for wide joints, rough or textured tile and stone that would be hard to clean after floating. See grout tools.
Grout float: A rectangular trowel-shaped tool with a firm rubber pad, used to pack grout into joints and remove the excess. Harder pads suit epoxy and urethane grouts, while softer gum-rubber pads suit cement grout. See grout tools.
Grout joint: The gap between adjacent tiles that is filled with grout. Its width is set by tile size, tile tolerances, layout and the installation standards. See the grout joint width guide.
Grout release: A temporary coating applied to tile faces before grouting so grout and pigment wipe off easily. It is useful on porous, textured or unsealed tile and stone that could otherwise stain from grout pigment. See grout for handmade and zellige tile.

H

Haze: The thin film of cement, polymer or resin left on tile faces after grouting. Cement haze is usually removed with a dry buff or a haze remover once the grout has set, while epoxy haze must be dealt with quickly. See how to remove grout haze.
High-performance cement grout: A polymer-modified cement grout meeting ANSI A118.7, with lower shrinkage, lower absorption and more consistent color than a standard A118.6 grout. Most current bagged grouts sold to professionals fall into this category. See high-performance cement grout.
Honeycombing: A porous, open-celled texture in a grout joint where the material did not consolidate fully. Common causes include grout mixed too wet, joints not packed firmly, or grout that was washed out with an overly wet sponge. It weakens the joint and traps dirt; see grout pinholes and voids.
Hydration: The chemical reaction between portland cement and water that forms the binding crystals in cement grout. Hydration needs water to continue, which is why grout that dries too fast ends up weak and powdery. See what grout is made of.
Hydro sponge: A dense, rounded-edge sponge made for grout cleanup that holds water without dumping it into the joints. Wringing it until nearly dry is key to avoiding washed-out joints and shading. See grout tools.

I

Impregnator: Another name for a penetrating sealer: a product that soaks into grout or stone and lines the pores with water and oil repellent, without forming a surface film. It leaves the appearance largely unchanged. See penetrating vs membrane sealer.
Initial set: The point at which a fresh cement grout or mortar begins to stiffen and loses its plasticity. Cleaning and tooling are timed around it: too early and the sponge drags grout out, too late and haze is hard to remove. See how to grout tile.
ISO 13007-3: The international standard that classifies tile grouts, the counterpart to the ANSI A118 grout standards. It uses CG1 and CG2 for cementitious grouts, suffixes W, A and F for added properties, and RG for reaction resin grouts. See grout standards explained.

J

Joint width: The distance between adjacent tile edges. ANSI A108.02 sets a minimum of 1/16 inch and requires joints at least three times the tile's actual facial dimensional variation, so less consistent tile needs wider joints. The joint width calculator applies that rule.

L

L/360: A deflection limit meaning the floor may bend no more than its span divided by 360 under design load. It is the usual minimum for ceramic and porcelain tile floors on wood framing. See floor grout.
L/720: A stricter deflection limit, span divided by 720, commonly cited for natural stone tile because stone is less tolerant of movement than porcelain. Meeting it often means additional subfloor layers or stiffer framing. See grout for natural stone.
Latex additive: A liquid polymer admix (often acrylic or styrene-butadiene) used in place of some or all mixing water in cement grout. It improves flexibility, bond, stain resistance and reduces absorption. Most modern grouts include dry polymer in the bag instead; see how to mix grout.
Lippage: The height difference between the edges of adjacent tiles. ANSI A108.02 allows about 1/32 inch for joints under 1/4 inch wide and 1/16 inch for wider joints, plus inherent tile warpage. Lippage is a setting issue that grout cannot fix; see the grout joint width guide.

M

Margin trowel: A narrow, flat, rectangular trowel used for mixing small batches, scraping buckets, and working grout into tight spots. It is also handy for packing grout into corners and around fixtures. See grout tools.
Mastic: A premixed organic tile adhesive that cures by drying, covered by ANSI A136.1. It suits small wall tile in dry areas, but is not recommended for submerged or continuously wet areas, floors or large-format tile. Compare setting materials in grout vs thinset vs mortar.
Membrane: A sheet or liquid-applied layer under the tile that provides waterproofing (ANSI A118.10) or crack isolation (ANSI A118.12). In showers, the membrane, not the grout, keeps water out of the structure. See shower grout.
Membrane sealer: A sealer that forms a film on top of the grout or tile rather than soaking in, also called a topical sealer. It can add sheen and strong stain resistance but may wear, peel or trap moisture. See penetrating vs membrane sealer.
Mildew: Surface fungal growth that appears as black, gray or green spotting on grout in damp areas such as showers. It feeds on soap residue and body oils, so cleaning and ventilation are the main cures. See grout mold and mildew.
Modified epoxy emulsion: A grout combining epoxy resin and hardener emulsion with portland cement and sand, standardized under ANSI A118.8. It sits between cement and true epoxy grout in stain and chemical resistance. See specialty grouts.
Mosaic: Small tiles, usually 2 inches or less, typically mounted on mesh or paper sheets. Mosaics have a high ratio of joint to tile, which raises grout consumption and makes grout choice more visible. See grout for mosaic tile.
Movement joint: A joint filled with flexible sealant instead of grout, placed so tile can expand and contract without cracking or tenting. TCNA EJ171 calls for them at perimeters, changes of plane, and at set intervals in large fields. See caulk vs grout for movement joints.

O

Open time: The working window after a material is spread during which it remains usable. For thinset it is how long the troweled bed will still bond to tile; for grout it describes how long the mix stays workable on the wall or floor before cleaning must start. See how to grout tile.
Oscillating tool: A power tool with a vibrating head that can take carbide or diamond grout removal blades. It removes grout much faster than a hand saw, but slipping out of the joint can chip tile edges. See how to remove grout.
Oxygen bleach: A cleaner based on sodium percarbonate, which releases hydrogen peroxide in water to lift organic stains and mildew. It is gentler on grout color than chlorine bleach. See how to clean grout.

P

Penetrating sealer: A sealer that soaks into grout and lines its pores with a water and oil repellent, usually silane, siloxane or fluoropolymer based. It slows absorption without forming a surface film and needs periodic reapplication. See how to seal grout.
Perimeter joint: The joint where a tiled field meets a wall, column, curb or other fixed element. It is a movement joint, so it is left open under baseboard or filled with sealant rather than grout. See caulk vs grout for movement joints.
pH-neutral: A cleaner with a pH near 7 that is safe for routine cleaning of grout, sealers and most stone. It will not etch calcareous stone or strip penetrating sealers. See grout cleaners by pH.
Pigment: Finely ground coloring agent, usually mineral oxides, added to grout to produce its color. Uneven water content during mixing and cleanup can change how pigment reads and produces blotchy color. See the grout color guide.
Pinholes: Tiny holes in the surface of grout joints. They usually come from trapped air, overwatering during sponging, or air escaping from the substrate or thinset. See grout pinholes and voids.
Polymer additive: A redispersible polymer powder or liquid latex added to cement grout to improve flexibility, bond, and resistance to water and stains. It is what separates most A118.7 grouts from plain A118.6 grouts. See what grout is made of.
Porcelain tile: Dense ceramic tile with water absorption of 0.5 percent or less, as defined in ANSI A137.1. Its low absorption and often rectified edges affect grout choice and joint width. See grout for porcelain tile.
Portland cement: The hydraulic binder in cement grouts, made by firing limestone and clay and grinding the clinker with gypsum. It reacts with water (hydration) to form a hard matrix around the aggregate. See what grout is made of.
Pot life: How long a mixed batch remains usable in the bucket before it stiffens. It is critical with epoxy, where heat from the reaction shortens working time, especially in a full bucket or warm room. See how to apply epoxy grout.
Premixed grout: Grout sold ready to use in a bucket, typically a single-component product based on acrylic, urethane or similar resin binders. It eliminates mixing and offers consistent color, but cure depends on drying or reaction, which varies by product. See premixed grout.

R

Rapid-setting grout: A cement grout formulated to set and gain strength much faster than standard grout, often allowing traffic within a few hours. It is classed F under ISO 13007-3 and has a shorter working time. See specialty grouts.
Rectified tile: Tile whose edges have been mechanically ground or cut after firing to produce precise, square dimensions. Rectified tile allows narrower joints, but ANSI A108.02 still sets a minimum of 1/16 inch. See the grout joint width guide.
Regrouting: Removing old or damaged grout to a sufficient depth and filling the joints with new grout. It is a fix for cracked, stained or crumbling grout when the tile itself is sound. See how to regrout tile.
RG: The ISO 13007-3 class for reaction resin grout, covering epoxy and similar resin-based grouts. It is the rough counterpart to ANSI A118.3. See grout standards explained.

S

Sanded grout: Cement grout containing graded silica sand, used for joints of about 1/8 inch and wider (many products go to 1/2 inch; check the TDS). The sand resists shrinkage and cracking in wide joints but can scratch polished marble, glass and high-gloss tile. See sanded grout.
Scrub pad: A non-scratch nylon pad used to clean grout, remove light haze, or agitate cleaners. White pads are generally the least aggressive; harder colored pads can scratch glossy tile or stone, so test first. See how to remove grout haze.
Sealant: A flexible joint filler, typically silicone, urethane or acrylic, used in movement joints, changes of plane and perimeters. Sealant stays flexible as the tile and substrate move, where grout would crack. See caulk vs grout for movement joints.
Shading: Uneven color in cured cement grout, often appearing as lighter or darker patches. It is caused by inconsistent water content, uneven drying, or overwatering during cleanup. See grout discoloration and shading.
Shrinkage: The reduction in volume as grout cures and loses water, which can open hairline cracks or pull grout away from tile edges. Too much water in the mix makes it worse. See why grout cracks.
Silica sand: The quartz sand used as aggregate in sanded grout. Its graded particle sizes give strength and resistance to shrinkage in wider joints. Dry mixing and grout removal can produce respirable silica dust, so use dust control and a suitable respirator; see what grout is made of.
Siliceous stone: Natural stone composed mainly of silicate minerals, such as granite, quartzite and most slate. It is generally more acid resistant than calcareous stone, although some varieties contain calcite or iron. See grout for natural stone.
Slaking: Letting freshly mixed cement grout rest for the time listed on the TDS, often about 5 to 10 minutes, so the chemicals and polymers hydrate fully. After slaking the grout is remixed briefly, without adding more water. See how to mix grout.
Soft joint: Trade term for a movement joint filled with flexible sealant instead of grout. Soft joints are used at changes of plane, perimeters and at planned intervals in large tile fields. See caulk vs grout for movement joints.
Striking: Shaping and compacting the surface of a grout joint with a tool or rounded edge once the grout has firmed, also called tooling. It gives a uniform profile and helps densify the joint surface. See how to grout tile.
Substrate: The surface that tile is installed on, such as concrete slab, cement board, backer board or a membrane over a subfloor. Grout performance depends on the substrate being stable, flat and properly cured. See why grout cracks.
Sulfamic acid: A granular acid used diluted to remove cement haze and efflorescence from acid-tolerant tile. It is milder than muriatic acid but will etch calcareous stone and can attack cement grout if left too long. See efflorescence on grout.

T

TCNA Handbook: The Tile Council of North America Handbook for Ceramic, Glass, and Stone Tile Installation, a reference of installation methods and guidance. Its EJ171 section covers movement joint design and placement. See caulk vs grout for movement joints.
Technical data sheet: The manufacturer document (TDS) listing a product's standards, mixing ratio, joint width range, working time and cure times. It is the final reference for any grout, since products vary. See grout product lines compared.
Thinset: A cement-based tile mortar troweled in a thin layer to bond tile to the substrate, covered by ANSI A118.1 (unmodified) and A118.4 or A118.15 (modified). It is not interchangeable with grout. See grout vs thinset vs mortar.
Tooling: Another term for striking: smoothing and compacting the grout joint surface with a tool after it firms. Consistent tooling helps keep joint depth and color even. See how to grout tile.
Topical sealer: A sealer that forms a film on the surface instead of soaking in, also called a membrane sealer. It can change appearance and may need stripping when it wears. See how to remove grout sealer.

U

Unsanded grout: Cement grout without sand aggregate, used for joints under about 1/8 inch. Its fine texture fills narrow joints and is safer on polished or easily scratched surfaces. See unsanded grout.
Urethane grout: A grout using a urethane or similar resin binder, often sold premixed. It typically offers good stain resistance and color consistency with simpler cleanup than epoxy. See urethane grout.

W

W (ISO class): The ISO 13007-3 suffix for reduced water absorption in an improved cementitious grout, as in CG2W or CG2WA. It is a useful marker for showers, kitchens and exterior work. See grout standards explained.
Water-cement ratio: The proportion of water to cement in a grout mix. Too much water weakens grout, increases shrinkage, raises porosity and makes color uneven. See how to mix grout.