Preventing Grout Cracking/Discoloration -- To prevent cracking and discoloration, flexible caulking -- rather than Portland cement grout -- should have been used in this shower where the floor tiles meet the wall tiles.

Proper post-installation cleanup helps regulate the depth of the grout within tile joints and promotes adequate curing.

However, I can identify the least popular — but most seen — grout color. Care to guess what it is? It’s mop water gray. Because it’s porous, Portland cement floor tile grout is absorptive and subject to frequent cleanings by mop. Those cleanings are what turns the grout gray in color.

Now, let’s examine other problems with grout color. First, consider that most of your dry-set grouts are pre-mixed by the manufacturer. Job site mixes are usually white or gray to match the color of the cement. In addition, sanded and unsanded grouts are available.

Unsanded grouts are used in grout joints less than 1/8 inch wide. They are also used in wall applications because the “mix” fits the grout joint and does not scratch glazed tile.

Both varieties of grout are used in floor joints to provide greater strength and resistance to wear. They are also less expensive than the unsanded variety.

These grouts are usually mixed with water only. However, when an acrylic admix is used, the grout will become denser and less absorbent. It will also better bond to the edges of the tile. Finally, because less water is used in the mix, the acrylic additive reduces grout cracking and extends the life of its color.

With the introduction of designer colors and, consequently, lighter shades, consumer dissatisfaction with Portland cement grout color has become chronic. Many reasons account for grout discoloration or inconsistent color. Here are a few them:

• Overglaze on the tile edges, which retards even setting (hydration) of the grout.
• Setting material (mortar) too high in the joints.
• Excessive use of water during cleanup.
• Poor mixing procedure.
• Grout mixed with too much water.
• Grout allowed to dry too quickly. Grout should always be moist cured.
• Grouting done on different days. (A difference in shading may even become evident when one wall is grouted early in the day and a second wall is grouted in the afternoon. Ambient humidity can play a significant role in the process)
• Use of cleaners before curing is complete.
• Use of old grout that has settled in its container and requires dry mixing.
• Organic setting mastics.
• Regional water differences.
• Inorganic materials surfacing from the setting bed.

The introduction of fast-setting grouts that have initial setting times of as few as three hours are among the newest developments in this product category. These grouts should not contribute to efflorescence, although efflorescence may still arise from a setting bed source.

Beyond discoloration, it is important to know that where joints meet horizontally and vertically, a flexible caulking material must be substituted in place of the hard-setting Portland cement grout. Settling, cracking and/or any structural movement will cause either separation of the grout joint or cracking. When this occurs, water can intrude and not only cause structural damage to the wall but also become a source of mold and mildew growth. This is a real concern.

Often, a grout line will crack because it is too thin. This is usually a result of the setting material occupying too much of the grout joint. Two-thirds of the tile thickness must be maintained as the joint space if the grout is to develop adequate strength. If the depth is any shallower, the hydration process stops sooner and the grout’s ultimate strength is diminished. This is why it is essential to damp cure.

So, as you can see, proper application becomes a very large part of maintaining the color and shade of your grout. Don’t go gray prematurely!