How Much Stone Do You Need to Fill a Gabion Basket?

Gabion baskets have become a popular choice for home and landscape projects needing sturdy retaining walls, drainage solutions, or decorative garden features. This guide will walk you through how to calculate the gabion stone fill you’ll need based on the basket dimensions. We’ll also cover stone types, sourcing, costs and proper filling techniques.

What are Gabion Baskets?

Gabion baskets are wire cages made from welded steel wire mesh that can be filled with rocks to create gabion walls, retaining walls, garden beds and more. The cages come in varying sizes and mesh thicknesses, such as 3mm or 4mm gabion wire on our site, and they are all galfan coated for durability.

Once filled tightly with hard, durable rocks, the stone cages stack together like building blocks, interlocking to form strong, long-lasting structures. The wired walls help contain the rocks while still allowing drainage.

Calculating Gabion Stone Volume or Weight

The amount of stone you'll need to fill a gabion basket depends on its dimensions and the type of stone you choose. Follow these steps to calculate the required volume of gabion stone:

1. Measuring Gabion Basket Dimensions

Before calculating the stone volume or weight, measure your gabion basket's dimensions in meters. The basket's size determines the amount of stone needed.

2. Calculate Gabion Cage Volume

Multiply the length, width, and height of your gabion basket to find its volume in cubic meters. For instance, a 2m x 1m x 0.5m gabion basket equals 1 cubic meter in volume.

3. Determining Stone Amount

Use the following formula to estimate the stone volume required:

stone_volume = gabion_volume (1 - (stone_size / 1000) * 3)

For a 1 cubic meter gabion basket with 100-200mm stones, the stone volume is approximately 0.999 cubic meters. Here is a table of the amount of stone you will need for different gabion basket volumes and stone sizes:

4. Calculating Stone Weight

To calculate the amount of gabion stone in tonnes, You'll need to know the bulk density of the specific stone you're using. Bulk density, sometimes referred to as unit weight, represents the mass of a substance (in this case, stone) per unit volume (typically measured in kilograms per cubic meter or metric tonnes per cubic meter).

Bulk density is usually measured in kilograms per cubic meter (kg/m³) or metric tonnes per cubic meter (t/m³). Check with your stone supplier for this information. For example, if the bulk density of your chosen stone is 1.6 t/m³:

stone_tonnes = stone_volume * unit_weight_of_stone

Common Unit Weights of Gabion Stone

• Limestone: The bulk density falls within the range of 2.2 to 2.8 t/m³.
• Granite: Granite is a dense stone, and its bulk density ranges from 2.6 to 2.8 t/m³.
• Sandstone: The bulk density of sandstone ranges from 2.0 to 2.5 t/m³.
• Slate: Slate typically has a bulk density ranging from 2.7 to 2.8 t/m³.

Additional Tips

• Always round up to the nearest tonne.
• Allow for extra stone for breakage or waste.
• For different stone sizes, calculate each size and add them together.
• For large gabion projects using stacked baskets, calculate the volume for each individual cage. Add them together for the total stone amount required.
• Buying gabion fill stone in bulk bags is most cost-effective for multiple basket projects.

Choosing the Right Gabion Fill Stone

Construction-grade aggregates and quarry stones work well for filling gabion baskets. Avoid very fine materials like gravel or pebbles that can be pushed out. Ideally, the rock should be hard, dense, and weather-resistant. Granite, basalt, and limestone are good options.

A general rule of thumb is to select stones that are a bigger size than the mesh opening. This ensures that the stones can't slip through the mesh easily. For example, if your mesh size is 76mm x 76mm, aim for stones sized 100-200mm.

Consider the shape of the stones as well. Irregularly shaped stones with flat sides tend to interlock better and provide stability. Avoid very round stones that may not stack well. Gabion fill doesn’t need to be decorative or uniform in colour. It just needs to be durable, sized properly and resist shifting once packed into the baskets.

Sourcing Gabion Fill Stone

Check with local quarries or landscape/masonry supply shops to source gabion-grade fill stone in bulk cubic meters at the lowest costs. For small DIY cages, some nurseries may sell bags by weight. Calculate delivery fees into your project budget or opt to pick up the stone yourself to save costs.

If harvesting rock on your property, test it to ensure it’s hard, non-porous, and weather-resistant. Avoid any soft, crumbling, or flaky rock.

Proper Gabion Filling Method

When filling gabion baskets, tightly pack the rock so the structure remains stable:

• Fill in layers, tamping down periodically.
• Brace baskets with rebar pins to prevent bulging.
• Overlap and interlock stones to leave no gaps.
• For large baskets, use temporary dividers then remove them once filled.
• Tightly pack the bottom 2/3 only, the top can be more loosely filled to save costs.

Follow the measuring, ordering and packing steps to create durable gabion baskets that stand the test of time. Pack the stones in tight layers to create a robust, interlocking system within the baskets. Our step-by-step installation guide walks you through constructing sturdy gabion wire cages. The effort spent on correct filling results in quality, long-lasting gabion projects. Once your baskets are filled, check out our guide on building gabion retaining walls.