Grass joints are very decorative—the green color provides a beautiful contrast to the slate. The surface becomes very stable because the slate “grows” firmly in the joints.

We recommend seeding the grass rather than waiting for it to grow by itself, as you will likely end up with a fair amount of weeds if you do.

Use seeds for low-growing grass and mix them in a bucket with soil.

Compress the soil well into the joints with your fingers.

Don’t fill more than that which leaves a minimum 5mm edge to avoid soil and seeds being washed out.

It will take some time for germination and growth, and during this period, it may become a bit messy, especially with heavy rainfall. Going forward, the grass will need to be mowed; otherwise, it will grow onto the slabs.

Sedum are plants from the stonecrop family. This is a green solution that is becoming increasingly popular. These plants thrive in nutrient-poor, dry soil and are therefore well-suited for places where it is usually difficult to get plants to grow.

The advantage is that it is very decorative and easy to maintain. Sedum grows extremely well with slate, partly because slate stores heat, providing optimal growth conditions. It grows densely and crowds out weeds. Sedum has beautiful colors that change with the seasons.

This solution works very well as an ending for a slate paving area against a lawn or rock. But you can also use it in the joints themselves if you have a large enough joint width, i.e., at least 3 cm.

Sedum is available in pre-grown mats with a variety of species that bloom at different times.

• Lay down a strip of geotextile fabric in the joint.
• Add a bit of soil.
• Tear off a suitable piece of the sedum mat and plant it in the joint. Press down well and add more soil if necessary.
• Water after planting so the roots can establish themselves.

Fine gravel provides a very clean look and is easy to maintain.

Using fine gravel, which is a mix with a lot of fines, will settle well in the joints and become nearly solid. The advantage is that you can fill the joints almost completely. The downside is that it can create some mess during rain—fines in the fine gravel can wash out onto the slate.

• Spread fine gravel over the joints, and brush it into the joints.
• Go over the joints until they seem saturated, filling them to the top.
• Lightly spray with water and let it settle for a few days.
• Check and fill in as needed until the material has settled.

Using gravel in the joints gives a very clean look and is easy to maintain.

Using gravel, such as a fraction of 2–8 mm, will provide a draining joint. The advantage is that water will flow through the joint. This creates a very clean surface, as long as you do not overfill the joints. If you do, gravel may spread out. Gravel also requires relatively narrow joints, up to a maximum of 2 cm, for the same reason.

• Spread gravel over the joints, and brush it into the joints.
• Go over the joints until they seem saturated, but do not fill higher than about 5 mm below the surface of the slate.
• Lightly spray with water and let it settle for a few days.
• Continue to check and fill in as needed, and repeat with a bit of watering as necessary.

There are joint fillers that cure and can still be used on slate laid on the ground, i.e., in loose material, because they can tolerate movement and are flexible.

This provides a very clean look. You get a tight and firm joint similar to a cement joint, so using this method requires that the surface has good drainage.

• Distribute the joint filler and sweep it into the slate in both directions until the joint is filled.
• Leave some excess on the surface.
• Compact the material with a jointing tool.
• Carefully fill the joint and thoroughly clean the surface.
• Gently spray with a hose or spray bottle until the material is fully saturated without the sand flowing out.
• Remove any excess wet material with a soft brush or light rinsing.
• Curing time is 1-3 days depending on temperature and humidity. Follow the manufacturer’s instructions.