Gabion stones: which size to choose? Calculate filling quantities correctly

2024 Author: Caroline Blare | [email protected]. Last modified: 2024-01-31 11:14

More and more people are looking for an alternative to the classic wooden fence and are becoming aware of gabion fences. These are wire cages in different sizes and shapes that are filled with gabion stones and therefore look like an elegant stone wall. Property owners and garden enthusiasts who decide to use gabion stones should pay attention to the appropriate stone size and their filling quantities.

Gabion stones in detail

Gabion stones are easy-to-erect stone wall variants that can be easily erected and filled even without any knowledge of wall construction. The fences consist of a wire basket that is filled with rubble stones of different grain sizes, creating the impression of a wall. Not only quarry stones are used here, but also gravel, which is quite coarse-grained and can therefore easily be used for the gabions. The following stones are ideal and have established themselves as filling material:

Granite
Dolomite
Sandstone
Quartz
Bas alt
Limestone
Greywacke
Ornamental gravel
Glass chunks (not rock, but often used for gabions)
Marble
Sugarstone
Muschelkalk

Due to this diversity, it is necessary to know how to calculate general filling quantities for gabion fences, as each stone has a different density and even fracture shape. You cannot order the same amount of marble as bas alt as the two stones are fundamentally different and it could easily happen that you receive too much or too little. This should be avoided at all costs, otherwise you will incur unnecessary costs. The difference between the different gabion stones becomes even clearer if you want a specific shape, for example very flat or roughly chipped stones with clearly visible edges.

Tip:

Before choosing the stones, you should find out what colors they can be delivered in. Maybe you like a rose quartz in delicate pink tones more than typical greywacke stones, which is important for the respective project.

Stone size

The correct size of the gabion stones is crucial for the necessary order quantity, as this determines how close together the stones are in the wire baskets. The size is also important so that the stones do not simply fall out of the holes in the gabion cages as soon as they are filled. This requires the dimensions of the respective mesh size, which you should check when purchasing the cages to find out the necessary stone size. The mesh size describes the distance between the wires. Typical mesh sizes are:

50 x 50 mm
50 x 100 mm
50 x 200 mm
100 x 100 mm

But there are other mesh sizes, ranging from small 30 x 60 mm to large 150 x 350 mm, which also influence the size of the stones. The stone size is measured based on the mesh size. For a gabion fence with a mesh size of 50 x 100 mm, you should choose stones whose grain size is at least the shortest width of the mesh. In this case, these would be gabion stones that have a grain size of 50 - 120 mm, for example, and cannot fall out during filling. However, the size can be influenced by the fineness of the grain:

coarse stones: usually larger, are further apart because edges are more misshapen, fewer stones are needed
fine stones: lie close together thanks to smoother edges, the shape of the stones is similar throughout, more stones are needed

You also have to make sure that the size of the stones is usually determined using a sieve measure. This means that the size given is only a guide, as natural stones are not identical in size unless they are processed. The following problems can occur:

Length, width or density of some stones do not fit
these can either not be used at all or can only be used after repeated attempts
fall out frequently
In extreme cases they can't even fit into the fence

This problem does not occur with processed stones that are uniform in shape. These can be easily stacked in the gabion baskets, but do not look as natural as the other stones. An example of this would be paving stones, although these are rarely used for gabions.

Tip:

If you no longer know what the mesh size of your gabion fence is, you can simply measure it with a tape measure or ruler.

Filling quantities

After you have decided on the right size of the stones, you then have to calculate the filling quantity. This information is important so that you have enough stones available to fill your gabions and the optimal filling quantity saves you time and money. The following sizes are required for the calculation:

Height of the gabions in meters
Width of the gabions in meters
Length of the gabions in meters
Weight of stones per cubic meter (m³) in tons

Many people have problems with this because they don't know how much the individual stones weigh. This information is easier to find than you think, because every manufacturer must specify the corresponding weight per cubic meter for the specific gabion stones. For example, a cubic meter of bas alt 60 – 300 mm weighs 1.5 tons per cubic meter, while a cubic meter of Jura boulders 45 – 56 mm weighs 1.4 tons. Although this looks like a small difference, it is crucial for the calculation. The formula is as follows:

Length x height x width x weight=result in tons

This means that if you have a gabion fence measuring 10m x 2m x 1m and use the Jura chunks mentioned above, you have to fill 20 m³ of fence, which corresponds to a whopping 28 tons. For Jura chunks in this quantity you will spend between 1,200 and 1,500 euros. Please make sure that, despite this exact calculation, you always order around 20 percent more stones, as some can be damaged during transport or do not completely fill the fence due to their shape. It can also happen that more stones are needed to fill corner connections. This is typical for this form of filling and therefore it is important not to forget this point.

Gabions: Calculate filling quantity - rectangle

The bill looks like this:

Result in tons + 20%=final filling quantity

With a quantity of 28 tons, 20 percent corresponds to 5.6 tons and so you end up with a filling quantity of 33.6 tons. Delivery costs vary depending on the retailer.

Tip:

If you have problems calculating the percentage, you can simply divide the result in tons by 5. The result corresponds to 20 percent.

Round gabions

When calculating the filling quantity for round gabion fences, things can often be a little more difficult. Since this is not a cuboid but a cylinder, the filling quantity must be calculated accordingly. Thanks to the circle number Pi (=3, 14159.), even basic round shapes can be easily calculated. If you have chosen a gabion fence whose base area corresponds to a circle, you will need the following values to calculate the room volume:

Radius of the circle
Height of the fence

The formula is as follows

Circle number Pi x Radius² x>

Gabions: Calculate filling quantity - round

With a circular gabion fence with a height of two meters and a radius of one meter, you have a volume of 6.3 cubic meters. Now you have to calculate this value together with the specific density of the stones per ton, so:

Volume x weight=capacity

If you take the above-mentioned Jura chunks 45 - 56 mm, which weigh 1.4 tons per cubic meter, you will get a capacity of 8.8 tons.

hollow cylinder

Since not every gabion fence is used as a pure cylinder, but rather as a hollow cylinder, you have to use a different formula for this:

Volume of the outer cylinder – Volume of the inner cylinder=Volume of the hollow cylinder

With a gabion fence that has an outer radius of two meters, an inner radius of one meter and a height of two meters, you get a volume of 18.8 cubic meters. Then multiply this value by the weight of the stones per ton and you get the filling quantity. With the Jura chunks already mentioned, that would be a capacity of 26.3 tons.