What is the Cost of a Gabion Wall?

The word “gabion” comes from the Italian gabbione, meaning “big cage”. Baskets filled with earth or stone have been used to protect riverbanks, including along the Nile, for thousands of years, and gabions were used in military fortifications for centuries. Civil engineers now use them to stabilise riverbanks, streams and highway embankments and to control erosion on slopes. A gabion wall is a gravity retaining structure: its own weight holds back the soil, and it is usually cheaper and quicker to build than a concrete wall.

Gabion walls are built mainly to retain the soil behind them, but they can also be used as a facing or cladding wall. The wall is made from gabion baskets laid in one or more rows, depending on its height. Each basket is a closed cage of galvanised (or PVC-coated) hexagonal wire mesh filled with broken rock. Stacking the baskets in a planned bond pattern, with each course stepped back on taller walls, gives a retaining structure that can replace concrete in many soil stabilisation jobs.

APPLICATIONS

• Retaining walls
• River and canal bank protection
• Erosion and scour protection for roads and bridges
• Hydraulic structures, check dams and culvert headwalls
• Coastal embankments
• Rockfall and soil erosion control
• Architectural cladding for walls and buildings
• Freestanding walls and noise barriers
• Landscape and garden features

Benefits of Gabion Walls

• Local materials: stone from site excavation or a nearby quarry can be used as fill, which cuts purchase and transport costs.
• Passive cooling: in hot climates, gabion facades are used as shading walls; the stone mass and the air moving through the voids help keep buildings cooler.
• Water passes through: gabion walls are permeable, so water flowing through them does not damage the structure.
• Vegetation: over time, soil and plants fill the voids, which helps the wall blend in and can bind the fill further.
• Longevity: hard, durable stone does not degrade, so the life of the wall is mostly set by the wire and its coating.

Gabion walls tolerate ground movement that would crack a rigid reinforced concrete wall.
A common gabion basket size is 2 x 1 x 1 m, made from double-twisted hexagonal galvanised mesh with an 8 x 10 cm opening.

How much does a Gabion Retaining Wall Cost?

The main factors that set the cost of a gabion retaining wall are:

• Length and overall size
• Height (taller walls need more courses, a wider base and usually an engineering design)
• The stone used as fill
• Design and consultant fees
• Excavation and drainage work

Of these, the price of a gabion retaining wall mostly comes down to two things: the stone and the size and complexity of the wall. Filling and lacing baskets is labour-intensive, so budget for labour. A curved wall costs more than a straight one. For a comparison with concrete walls, see are gabions cheaper than a retaining wall?

The Benefits of Having Gabions

1. Flexibility

Gabions have stayed in use because they are flexible as well as strong. Under high stress, a gabion basket deforms, bulges or compresses slightly instead of breaking, so the structure keeps working after movement that would crack a rigid wall. Because the wall is not rigidly fixed to a foundation, it can follow small ground movements and settlement.

2. Strength

The wire mesh is strong in tension and acts as reinforcement for the whole structure, not only as a container. As silt and roots fill the gaps between the stones, the wall can become more stable with age. The same strength makes small gabion baskets popular as bases for garden tables and benches.

3. Permeable

The gaps between the stones let air and water pass through the wall. A solid concrete wall without adequate drainage can build up hydrostatic pressure behind it, which adds load and can compromise it; a gabion wall drains freely, so that pressure does not build up.

4. Cost-effective

Wire mesh baskets cost less than most structural materials such as concrete, and small garden walls can be assembled without specialist skills, with no concrete to buy or mix. Fill such as stone or broken concrete can usually be sourced locally at low cost.

5. Firm Base

Gabion walls do not need a conventional concrete foundation. A levelled, compacted base, sometimes with a layer of crushed rock, is usually enough to give the baskets a firm footing. The bottom layer of stone beds into the prepared ground, and friction at the base keeps the baskets in place. Where the wall faces a river or stream, the toe also needs protection against scour, typically a gabion mattress apron, so that flowing water cannot undermine it.

6. Reduce Erosion

The main practical use of gabion walls is erosion protection. The stone fill absorbs and dissipates the energy of flowing water, which protects the bank or slope behind. That is why they are used to protect riverbanks and coasts, and why they suit a garden that runs down to a pond, stream or river.

7. Aesthetics

Although they are man-made, gabion walls look natural and can be matched to the local terrain by using local stone. Baskets come in many sizes and shapes, including curved units that form a bend when joined, and the fill can be chosen for colour, texture and size.

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