Filling the gaps in basalt paving stones, often called "jointing," is a crucial step. It locks the stones in place, prevents weed growth, stops ants from nesting, and creates a clean, finished look. Basalt is typically a dark gray/black stone, so the jointing material you choose will significantly impact the final aesthetic.
Here is a comprehensive guide on how to fill basalt paving stone gaps, covering the most common and effective methods.
1. Method: Polymeric Sand (Best for Tight Gaps)
Polymeric sand is a fine sand mixed with polymer additives. When water is applied, these polymers activate and bind the sand together, creating a solid, durable, and flexible joint that is highly resistant to weeds and insects.
Ideal for:
Gaps of 1/4 inch to 1.5 inches (check manufacturer's specs).
Patios, walkways, and driveways that need maximum stability.
Areas with high weed or ant problems.
Materials Needed:
Polymeric Sand (choose a color: gray or black are common for basalt)
A stiff broom or brush
A hand tamper or plate compactor (optional but recommended)
A hose with a misting nozzle or a sprinkler head attachment
A leaf blower or soft brush
Step-by-Step Process:
Preparation: Ensure the stones are completely dry and the gaps are free of debris, weeds, and old sand. Use a leaf blower or stiff brush to clean thoroughly.
Pour and Spread: Pour the polymeric sand over the paved area. Use a stiff broom to sweep the sand back and forth, working it deep into all the cracks. Avoid vigorous sweeping at this stage as it can pull sand out of the joints.
Compact the Sand: Once the joints are full, sweep diagonally across the pavers to remove all excess sand from the surface. Then, use a plate compactor (for large areas) or a hand tamper (for small areas). Place a scrap piece of plywood or a tamper mat over the stones first to protect them from scratches. This step vibrates the sand down into the joints, ensuring they are completely packed.
Final Cleanup: Gently use a leaf blower on a low setting to remove every speck of sand from the surface of the stones. This is critical. Any residual polymeric sand left on the pavers will harden and create a white, hazy film that is very difficult to remove.
Activation: Lightly mist the entire area with a fine mist of water from your hose. Do not use a strong jet stream, as it will wash the sand out. The goal is to gently soak the sand without creating puddles. Go over the area 2-3 times, waiting for the water to soak in between passes.
Curing: Keep the area completely dry for at least 24-48 hours (or as directed by the product instructions). Do not walk on it or let pets/rain onto it during this time.
2. Method: Jointing Grout for Pavers (Modern & Ultra-Durable)
This is a pre-mixed, cement-based material specifically designed for pavers. It's applied like a mortar and cures to a very strong, rigid finish. It's often used for contemporary designs with basalt.
Ideal for:
Very narrow gaps (but can handle wider ones).
Creating a modern, "grouted" look, almost like indoor tile.
Areas that require extreme durability.
Materials Needed:
Paver Jointing Grout (e.g., brands like ARCIS or SikaFastFix)
A grout bag (like a large piping bag) or a trowel and squeegee
A mixing bucket and drill paddle
A stiff brush and water for cleaning
Step-by-Step Process:
Preparation: The pavers must be thoroughly clean and completely dry. Any moisture will affect the curing of the grout.
Mixing: Follow the manufacturer's instructions precisely. Mix the grout to a smooth, paste-like consistency.
Application:
Grout Bag Method: Load the mix into the bag and pipe it directly into the joints, similar to icing a cake.
Squeegee Method: Pour the mix onto the pavers and use a rubber squeegee to push it into the gaps.
Tooling & Cleaning: Once the joints are full, use a strike tool or a rounded piece of hose to compact and smooth the grout line. Before the grout fully sets (check product for "open time"), use a stiff dry brush to scrub off any excess from the surface of the stones. A final light misting with water can help clean the residue and aid curing.
Curing: Protect the area from foot traffic and rain for the time specified by the manufacturer
3. Method: Stone Dust / Decomposed Granite (Traditional)
This is a more traditional and economical method. It creates a natural look but is not as stable or long-lasting as polymeric solutions.
Ideal for:
Informal garden paths or rustic settings.
Very tight budgets.
Areas where a more natural, permeable finish is desired.
Materials Needed:
Stone Dust or Decomposed Granite (DG)
A stiff broom
A plate compactor or hand tamper
A hose with a light spray nozzle
Step-by-Step Process:
Preparation: Clean the gaps as before.
Application: Spread the stone dust over the pavers and sweep it into the joints. Repeat until all joints are completely filled.
Compaction: Compact the area with a tamper to settle the dust.
Wetting: Lightly mist the entire area. The water will help the stone dust settle and lock together slightly. You will likely need to top up the joints after the first wetting and compact again, as the material will shrink as it settles.
Note: This material will eventually wash out or erode and will need to be topped up every few years. It is also more susceptible to weeds.
Choosing the Right Material Color for Basalt
Grey Polymeric Sand: The most common and safe choice. It will blend with the natural grey tones of the stone for a unified, minimalist look.
Black Polymeric Sand/Joint: Creates a high-contrast, dramatic "grid" effect. Excellent for modern and contemporary designs. It makes the dark basalt pavers truly pop.
Beige/Tan Jointing Material: Creates a very strong contrast. This can look fantastic but is a much bolder design choice. It works well in warmer climates or to complement light-colored house exteriors.
Pro Tips and Warnings:
Weather is Key: Never apply polymeric sand or grout if rain is forecast within the curing time. Do not work in direct, hot sunlight as it can cause the water to evaporate too quickly and prevent proper curing.
Protect Your Basalt: Basalt can be scratched by metal tools or aggressive brushing. Use plastic scrapers and soft-bristle brooms where possible.
Test First: Always test your chosen jointing material in a small, inconspicuous area to ensure you are happy with the color and application process.
Read the Instructions: Every product is different. The manufacturer's instructions on the bag are your most important guide for water amounts, curing times, and gap width suitability.
For more information about our products and services, please visit our website at www.magicstonegarden.com.
Written by Adeline Shi
Post time: Sep-23-2025