What Is the Best Grout Between Flagstones?

One of the top choices for grouting flagstones is epoxy grout. Epoxy grout is a type of grout that’s made from a combination of epoxy resins and fillers. It’s known for it’s strength and ability to form impermeable seams. This means that once the epoxy grout is applied, it creates a watertight seal between the stones, preventing any moisture from seeping in.

What Kind of Grout Do You Use for Flagstone?

When it comes to grouting flagstones, it’s essential to choose the right type of grout for the varying thickness and width of the joints. The best grout for this purpose is the one that’s a greater ratio of sand to cement. This ratio helps to fill in the larger gaps between the flagstones more effectively, ensuring stability and durability.

If you’re looking for a specific color and more consistency in your grout, there are specialized grout manufacturers that produce a type of grout specifically designed for wide joints over ½ inch wide. This variety of grout, often referred to as Saltillo grout, not only offers superior strength but also provides a range of color options to match or complement the color of your flagstone.

Natural flagstone, for example, requires a more flexible grout that can accommodate the natural movement and shifting of the stones.

This includes mixing the grout to the appropriate consistency and applying it properly, ensuring that all joints are adequately filled.

Additionally, consider the type of flagstone and follow the manufacturers instructions to achieve the best results.

How to Properly Mix Grout for Flagstone

When it comes to flagstone, it’s important to mix your grout properly to ensure the best results.

First, gather all the necessary materials: grout powder, water, a mixing container, and a stirring tool. Follow the manufacturer’s instructions on the grout packaging for the correct water-to-powder ratio, as it may vary depending on the brand.

Begin by pouring the recommended amount of water into the mixing container. Then, gradually add the grout powder while stirring continuously. Make sure to mix thoroughly to eliminate any lumps or dry spots.

Once the grout is well mixed, let it rest for a few minutes to allow the chemicals to activate. During this time, avoid adding more water or powder to the mixture.

After the resting period, give the grout another thorough stir to achieve a smooth consistency. The grout should be thick enough to hold it’s shape but still spread easily.

Once your grout is ready, use a grout float or a trowel to apply it onto the flagstone surface. Push the grout into the gaps between the stones, ensuring they’re completely filled. Be careful not to leave any air pockets or voids.

Finally, use a damp sponge or cloth to wipe away any excess grout from the flagstone surface. Rinse and wring out the sponge frequently to achieve a clean finish.

Remember to follow any specific instructions provided by the manufacturer for curing time and sealing the grout, as these steps can vary. Following the proper grout mixing technique will help you achieve the best results and ensure a strong and durable bond between your flagstones.

When it comes to filling the gaps between flagstones, stone dust emerges as a popular choice, particularly for flagstones with irregular shapes. The use of stone dust provides several advantages, including improved stability and drainage, allowing for a durable and visually pleasing surface. However, there are also alternative materials worth exploring, all of which have their own unique characteristics and suitability depending on the specific project requirements. Let’s delve into the different options to determine which material best suits your needs.

What Is the Best Material Between Flagstones?

When it comes to choosing the best material to fill the gaps between flagstones, stone dust emerges as a top contender, especially for irregularly-shaped flagstones. Stone dust offers several advantages that make it an excellent choice for this purpose. Firstly, it’s fine texture allows it to settle tightly into the spaces between the stones, providing effective stabilization. This is particularly important for flagstones that have naturally uneven surfaces or irregular edges.

Another benefit of using stone dust as grout is it’s natural appearance, which complements the natural beauty of flagstones.

However, it’s important to note that stone dust does have some limitations. For instance, since it isn’t a binding material, it may not be suitable for high-traffic areas or areas prone to heavy erosion, as it can wash away or be displaced over time. In such cases, a more durable grout material like sand-mix or mortar might be a better choice.

Pros and Cons of Using Sand-Mix as Grout Between Flagstones

  • Pros:
    • Natural appearance: Sand-mix grout blends well with the surrounding flagstones, providing a seamless and natural look.
    • Flexible: Sand-mix grout allows for some movement and flexibility between flagstones, reducing the risk of cracking or shifting.
    • Permeability: Sand-mix grout allows water to drain through, preventing pooling and potential damage to the flagstones.
    • Easy repair: If any flagstones crack or need to be replaced, sand-mix grout can be easily removed and re-applied without damaging the remaining grout.
  • Cons:
    • Higher maintenance: Sand-mix grout may require more frequent cleaning and reapplication to prevent weed growth and maintain it’s appearance.
    • Less stability: Compared to solid grout options, sand-mix grout may provide less stability and may not be suitable for heavy load-bearing areas.
    • Limited color options: Sand-mix grout typically comes in natural earth tones, limiting the range of color choices for matching or contrasting with the flagstones.
    • Potential erosion: Over time, sand-mix grout may erode or wash away, especially in areas with heavy rainfall or water flow, requiring periodic reapplication.

Another option for filling the gaps between flagstone is to use ground cover plants like moss or turf. Not only do these plants provide a natural and visually pleasing look, but they also serve as effective fillers for flagstone patios, especially when the stones are larger and spaced farther apart.

What Is the Best Material to Put Between Flagstone?

When it comes to choosing the best material to put between flagstones, ground cover plants such as moss or turf can serve as an excellent filler option. Not only do they provide a natural and organic look, but they also add a vibrant dash of color to the landscape. These options work particularly well for flagstone patios featuring large stones that are spaced far apart, as the plants can fill in the gaps and create a seamless, lush appearance.

One of the advantages of using turf as a filler material is it’s ability to withstand foot traffic. Turf is known for it’s durability, making it ideal for areas that experience heavy use. Additionally, it’s dense growth pattern helps to prevent weeds from sprouting between the flagstones, resulting in low maintenance and a tidy appearance.

On the other hand, moss is a great option for a softer and more natural look. It thrives in shady and moist environments, making it an ideal choice for areas with limited sunlight. Moss creates a lush carpet-like effect, which can soften the hard edges of the flagstones and add a touch of elegance to the patio. Furthermore, moss is relatively low maintenance and requires little watering, making it an excellent choice for those seeking a fuss-free filler option.

Source: What Material To Use Between Flagstones on a Patio

Starlike is a high-quality epoxy grout that’s highly recommended for exterior flagstone projects. It’s superior quality eliminates the need for sealing, making it the ideal choice for outdoor tile and mosaic installations. Now let’s delve into the reasons why Starlike is considered the best grout for this purpose.

What Is the Best Grout for Exterior Flagstone?

When it comes to choosing the best grout for exterior flagstone, it’s important to consider durability and weather resistance. One option that stands out is Starlike epoxy grout. This high-quality grout is specifically designed for outdoor tile and mosaic installations and doesn’t require sealing.

One of the key advantages of Starlike epoxy grout is it’s durability. Traditional cement-based grouts can deteriorate over time due to exposure to harsh weather conditions. It can withstand extreme temperature changes, UV rays, and heavy foot traffic, ensuring a long-lasting and beautiful outdoor grouting solution.

Unlike cement-based grouts that can absorb moisture and potentially lead to water damage, epoxy grout creates a waterproof barrier. This prevents water from seeping into the underlying structure and protects the flagstones from discoloration, mold, and mildew growth.

This grout is available in a wide range of colors, allowing you to achieve the desired aesthetic for your outdoor space. Furthermore, it’s effortless to clean, requiring only mild cleaning agents and a soft brush to maintain it’s pristine appearance.

It’s durability, resistance to water and weather, easy installation, and versatility make it a top choice for outdoor tile and mosaic installations.

Different Types of Grout for Outdoor Flagstone Installations

There are several different types of grout that can be used for outdoor flagstone installations. One common option is Portland cement-based grout, which is durable and can withstand heavy foot traffic. Another option is epoxy-based grout, which is highly resistant to stains and moisture, making it ideal for areas that are exposed to the elements. Additionally, there are polymer-modified grouts that offer improved flexibility and adhesion. When choosing the best grout for your flagstone project, consider factors such as the climate, expected foot traffic, and the appearance you want to achieve. Consulting with a professional or a knowledgeable supplier can help you make an informed decision.


It’s ability to form impermeable seams ensures that water and moisture won't seep through, preventing potential damage to the flagstones. Additionally, epoxy grout is highly resistant to staining, which is crucial when dealing with natural stone that may be susceptible to discoloration.

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