High-Performance Cement Grout (ANSI A118.7): What It Is and When to Use It

High-performance cement grout is a polymer-modified, cement-based grout that meets ANSI A118.7 (and usually ISO 13007-3 CG2WA). Compared with a standard A118.6 grout it cures with more consistent color, absorbs less water, shrinks less and resists abrasion better, while still cleaning up with water like ordinary grout.

What "high performance" actually means

For decades, cement grout in the US meant a blend of portland cement, sand or fine filler, pigment and a few additives, specified under ANSI A118.6. It worked, but it had familiar weaknesses: blotchy color when cleanup water varied, high absorption that let spills and soap soak in, and a tendency to powder or erode in high-traffic floors when it was overwatered.

ANSI A118.7, the standard for high-performance cement grouts, was written to capture a newer class of products. These grouts are still hydraulic (they harden by cement hydration, not by drying or a resin reaction), but their formulas are engineered around tighter performance limits. The standard addresses properties such as linear shrinkage, water absorption, compressive and flexural strength, and color consistency between samples. Exact test values and methods are in the current edition of the standard, which is periodically revised, so manufacturers' data sheets are the practical place to read the numbers a given product achieves.

The international equivalent is ISO 13007-3. A cement grout classified CG2 is an "improved" cementitious grout, and the suffixes W (reduced water absorption) and A (high abrasion resistance) describe exactly the gains a high-performance grout is designed for. Most products sold as high-performance in North America carry both labels. For a full breakdown of the classification letters, see our guide to grout standards (ANSI and ISO).

How it differs from standard cement grout

The differences come from what is in the bag. A standard A118.6 grout is mostly ordinary portland cement and aggregate. High-performance formulas typically add or change several ingredients:

• Redispersible polymer powder (often vinyl acetate-ethylene or acrylic types) that improves bond to tile edges, flexibility and resistance to water penetration. You add plain water, not a liquid latex additive.
• Blended or specialty cements, in many products including calcium aluminate or calcium sulfoaluminate cement alongside portland cement. These blends can speed the set and reduce the amount of free calcium hydroxide that causes efflorescence and shading.
• Water repellents built into the powder, so the cured grout beads water without a topical sealer.
• Finer, more tightly graded aggregate that packs densely and gives a smoother finish even in sanded versions.

The chemistry behind these ingredients is covered in what grout is made of. The practical result is a grout that behaves differently on the job, which is where most problems start.

Values are typical ranges for the category. Individual products vary widely, so always read the specific TDS. Our grout type property matrix compares more categories side by side.

When it is the right choice

High-performance cement grout has become the default for many professional setters because it closes most of the gap with epoxy at a fraction of the installation difficulty. It is especially well suited to:

• Floors with large porcelain tile, where narrow 1/16 to 1/8 inch joints are common and a single product that covers both narrow and wide joints simplifies the job. See grout for porcelain tile.
• Showers and wet walls where lower absorption means less soap scum and mildew getting into the grout body. It still needs a waterproofing membrane behind the tile; see shower grout.
• Dark or saturated colors, which are the most prone to shading and efflorescence in standard grouts.
• Kitchen floors and entries where you want good stain and abrasion resistance but the owner does not want the look or cost of epoxy.
• Exterior and freeze-thaw exposures, provided the specific product is rated for exterior use and the assembly has proper movement joints.

It is the wrong choice where acids, strong cleaners or food processing chemicals are routine (choose epoxy grout or an industrial system from specialty grouts), and in change-of-plane corners and perimeters, which need sealant rather than any grout.

Joint widths and the sanded vs unsanded question

The old rule of thumb (unsanded below 1/8 inch, sanded at 1/8 inch and wider) still applies to standard grouts and is explained in sanded vs unsanded grout. Many high-performance grouts sidestep it: a single formula with very fine, well-graded aggregate is rated for joints from roughly 1/16 inch to 1/2 inch. Some product lines still offer separate sanded and unsanded versions, and a few cap their range at 3/8 inch.

Two cautions apply. First, "fine aggregate" is still aggregate. On polished marble, glass, high-gloss glazes and soft metallic finishes, test on a spare tile before committing, because even fine grit can scratch when worked with a hard float. Second, at the wide end of the range, dense high-polymer grouts can show slight slumping or shrinkage dishing in deep joints if they are overwatered. The joint should be packed full to the tile edge and struck consistently. Use our joint width calculator to check what your tile's size variation actually requires.

Mixing: where most failures start

The single most common cause of a high-performance grout job that looks blotchy, powdery or soft is extra water. Standard grouts tolerate a splash more or less; these formulas are designed around a specific water-to-powder ratio, and polymer content plus fast-setting cement blends make them sensitive to deviation.

1. Measure water by volume or weight. Use the TDS figure for the bag size (for example, a stated number of quarts per 25 lb bag) and a marked container. Pour most of it in first, holding back a small portion.
2. Add powder to water. This wets the powder evenly and reduces lumps. Mix with a paddle at low speed, typically under 300 rpm, to avoid whipping in air that leads to pinholes and voids.
3. Slake if the TDS says so. Some products call for a short rest (often a few minutes) and a brief remix; others say not to slake. Follow the specific instruction.
4. Adjust only within the stated range. If the mix is too stiff, add some of the held-back water. Never exceed the maximum on the TDS.
5. Do not retemper. Once the mix starts to stiffen in the pail, adding water and remixing weakens it and can change its color. Mix smaller batches instead.

For general mixing technique across all grout types, see how to mix grout.

Installation and cleanup

Application is the same as for any cement grout: pack the joints diagonally with a rubber float, remove excess, then wash. The differences are in timing and water.

• Work smaller areas. Pot life and open time are shorter than with standard grout, often 20-30 minutes on the wall before cleanup should begin, and shorter in heat. In hot conditions the window can collapse; see grouting in hot and cold weather.
• Use a damp, not wet, sponge. Wring the sponge until it barely drips. Excess sponge water drags pigment and polymer to the surface, which is a leading cause of light, chalky or streaky joints.
• Change rinse water often. Polymer-rich slurry in dirty water leaves a haze that is harder to remove than plain cement haze.
• Buff haze early. Many high-performance grouts leave a polymer film that should be buffed off with a dry microfiber cloth within the window on the TDS. Haze left overnight may need a manufacturer-recommended haze remover. See how to remove grout haze.

Cure times and whether to seal

Fast-setting blends make many high-performance grouts ready for light foot traffic in roughly 3-24 hours and for full service, including showers, in about 72 hours or up to 7 days, depending on the product and temperature. Cold, damp rooms slow everything. Check the TDS, and plan with our grout cure planner or the detail in grout cure time.

On sealing, manufacturers differ. Many state that their high-performance grout does not require a sealer for normal residential use because of built-in water repellency, while still permitting a penetrating sealer for extra stain protection. If you seal, wait the full cure period the TDS specifies (often 48-72 hours, sometimes longer) and use a penetrating, breathable product. Our guide do you need to seal grout covers the decision in detail.

Common failure modes and their causes

Notice that most of these trace back to water and timing, not to the grout itself. The product is designed to perform within a narrow window, and staying inside it is the whole job.

Reading the bag and the data sheet

When comparing products, look past the front of the bag and check these items on the TDS:

• Standards met: ANSI A118.7 and the ISO 13007-3 class (CG2WA is the common target).
• Joint width range and any restrictions for glass, polished stone or soft-glazed tile.
• Mixing water per bag, pot life, time before cleanup and time to traffic, all at a stated temperature (usually 70-73 deg F).
• Whether sealing is required, optional or not recommended.
• Exterior, submerged (pool) and steam room suitability, each of which is a separate claim.
• Coverage figures. You can estimate quantity with our grout calculator.