29.06.2026

Gabion Foundations: Materials, Details, and Practical Applications

Building design

Modern structures featuring gabion walls and wooden roofs—an unusual architectural solution. (Photo: stadinstudio/Unsplash)

Gabions are among the oldest construction principles in civil engineering and landscaping: wire baskets filled with stones that derive their stability from their own weight. But as robust as the finished structure may appear, its durability depends crucially on an element that is completely invisible once construction is complete: the gabion foundation. Anyone who underestimates the importance of a gabion wall’s foundation risks settlement, tilting, and structural damage—issues that often don’t become apparent until years later, but are then costly and time-consuming to repair.

What a gabion foundation is and what structural functions it fulfills
Which foundation types are suitable for gabion structures and when each type is used
Which materials and layer configurations are critical for the foundation
How frost protection, drainage, and load transfer are structurally addressed
Which design principles, standards, and guidelines are relevant
How the construction process works step by step and what mistakes frequently occur in practice
How to design gabion foundations for different terrain conditions and soil classes
What role the gabion foundation plays in the context of slope stabilization, retaining walls, and fencing

What is a gabion foundation, and why is it indispensable?

A gabion wall is a heavy-duty structure: It does not transfer loads via tensile forces or fasteners, but exclusively through its own weight and the friction between the baskets and the subgrade. The gabion foundation is the layer or structural element that evenly transfers these loads into the load-bearing subgrade while simultaneously preventing frost, water, or settlement from destabilizing the structure. Without a properly planned and executed foundation, any gabion wall—regardless of its height or fill material—is at risk in the long term.

The term “gabion foundation” does not necessarily refer to a concrete foundation in the traditional sense. In the practice of landscape and civil engineering, it refers to the entire foundation structure: the excavation depth, the base layer of frost-resistant material, a concrete slab or concrete base if necessary, and the drainage layer. Depending on the wall height, soil class, and site conditions, this structure can be very simple or quite complex. The decision regarding this is not a matter of a craftsman’s discretion but rather an engineering planning task.

Gabion walls are used outdoors for a wide variety of purposes: as retaining walls for slope stabilization, as fences and privacy screens, as noise barriers along roadways, as terracing elements in gardens and open spaces, and as decorative room dividers in public open spaces. Each of these applications has specific requirements for the gabion foundation, as height, load, water conditions, and terrain vary significantly.

Soil Classes, Bearing Capacity, and Geotechnical Fundamentals

Every foundation design begins with an understanding of the subsoil. DIN 18300 classifies soils into soil classes based on their workability and structural properties, which are relevant for the execution of excavation work. In addition, the key parameters of soil mechanics are crucial for assessing bearing capacity: the angle of internal friction, cohesion, and the allowable base pressure. The latter indicates the load per unit area that a soil can support without experiencing unacceptable settlement.

Cohesive soils such as clay and loam are particularly problematic because they change volume with fluctuations in moisture, freeze during frost, and yield when thawing. On such soils, a gabion foundation without an adequate frost protection layer and drainage is not structurally stable in the long term. Non-cohesive soils such as gravel and sand are well-drained and frost-resistant, provided they are sufficiently compacted. Natural bedrock offers the highest load-bearing capacity but may require special drainage measures, as water cannot seep through rock.

For gabion walls up to a height of about one meter—such as those commonly used as fences or terracing elements in private gardens and public open spaces—a carefully constructed gravel layer is often sufficient as a foundation. For walls taller than one meter and in unfavorable soil conditions, professional planners generally recommend a foundation depth below the local frost line, as well as structural stabilization using a concrete foundation or a reinforced concrete slab. In Germany, the local frost depth ranges from eighty centimeters to one meter twenty, depending on the region; in exposed locations, it can be greater.

Foundation Types for Gabion Walls: Gravel, Concrete, and Combination Solutions

The simplest gabion foundation is a gravel foundation: The soil is excavated to the required depth, the excavated material is replaced with compacted gravel, and the bottom layer of gabions is placed directly on this layer. This solution is cost-effective, provides good drainage, and is suitable for lightweight structures on load-bearing, non-cohesive subsoil. It requires sufficient compaction of the gravel, which should be performed using a vibratory plate compactor in layers no more than twenty centimeters thick. An insufficiently compacted gravel base will settle under load, leading to tilting and gaps in the gabion wall.

The concrete foundation is the more robust solution and is better suited for taller walls and unfavorable soil conditions. It is constructed as a strip foundation along the entire length of the wall or as a slab foundation. The width of the concrete foundation should extend at least ten to fifteen centimeters beyond the width of the bottommost gabion layer on each side to ensure even load distribution. The concrete quality generally corresponds to exterior concrete of exposure class XF (frost-exposed), as the foundation is permanently exposed to moisture and frost. Reinforcement is often not strictly necessary for strip foundations for gabion walls up to a height of about two meters, but should be used in cases of uneven subsoil, for retaining walls subject to earth pressure, and for longer wall lengths.

A combination solution that has proven effective in practice combines the drainage function of the gravel with the positional stability of the concrete: A thin concrete slab or a lean concrete base is poured onto the compacted gravel bed, serving as a level, stable support for the bottommost gabion layer. This solution is particularly useful when the subgrade is slightly uneven or non-uniform, as the concrete layer compensates for unevenness and creates a defined support surface. The gravel beneath the concrete continues to perform the drainage function and prevents standing water from accumulating under the foundation.

Special Case: Slopes and Retaining Walls

Gabions used as retaining walls on slopes present greater structural challenges than freestanding enclosures because, in addition to the structure’s own weight, they must also bear the active earth pressure from the terrain behind them. In this case, the gabion foundation must be deep and wide enough so that the resultant force from the structure’s own weight and earth pressure remains within the foundation area, thereby preventing the structure from tipping or sliding. For retaining walls approximately one meter fifty in height or taller, an engineering calculation based on the principles of geotechnical engineering is required; the rules of the art refer here to DIN EN 1997 (Eurocode 7) as the normative basis for geotechnical design.

On slopes, drainage behind and beneath the gabion wall is particularly critical. Pressurized slope water significantly increases earth pressure and can destabilize even a correctly dimensioned structure. Therefore, a drainage layer of gravel or crushed stone is typically installed behind the gabion wall to divert the slope water laterally and minimize the water pressure on the rear of the wall. This drainage layer is separated from the surrounding soil by a geotextile (filter fabric) to prevent fine particles from entering the drainage system. On slopes, the gabion foundation itself should be set deeper on the valley side than on the mountain side to prevent scouring and erosion beneath the foundation.

Materials for the gabion foundation: crushed stone, concrete, and geotextiles

The choice of materials for the gabion foundation is based on clear functional requirements. Frost-resistant gravel, also known as frost-protection gravel, consists of crushed or natural gravel-sand mixtures with a defined grain size distribution that ensures good compactability and, at the same time, sufficient water permeability. Suitable grain sizes typically range from zero to sixteen millimeters or zero to thirty-two millimeters. It is crucial that the material be frost-resistant, meaning it contains less than fifteen percent of fine particles smaller than zero point zero seven five millimeters, since fine particles absorb water by capillary action and freeze when exposed to frost.

For the concrete foundation, standard concrete of strength class C16/20 or C20/25 is generally used. In cases of direct ground contact and frost exposure, exposure class XF2 or XF3 should be selected, which ensures increased resistance to frost and de-icing salt. The concrete is usually poured on site; for smaller projects and simple conditions, ready-mix concrete is also suitable. After curing, the concrete surface should be level and dimensionally stable to ensure an even bearing surface for the bottommost layer of gabions.

Geotextiles play an important, though often underestimated, role in foundation construction. When used as a separation layer between the natural soil and the gravel layer, they prevent soil material from mixing into the gravel, which would preserve the drainage capacity and bearing capacity of the gravel layer in the long term. When used as a filter geotextile behind gabion walls, they separate the drainage structure from the surrounding soil. The selection of the geotextile is based on the aperture size criterion: The characteristic aperture size of the geotextile must be smaller than the dominant grain size of the soil to be filtered in order to prevent suffosion (the washing out of fine grains).

Step-by-Step Guide: From Excavation to the First Gabion Layer

The construction of a gabion foundation begins with the precise staking out of the foundation axis and the determination of the excavation depth. The excavation depth depends on the local frost depth, the required thickness of the gravel layer, and the foundation thickness. In practice, the total excavation depth for a simple gabion wall up to one meter in height on frost-free ground is often between fifty and eighty centimeters; for taller walls and unfavorable soils, it can be one meter or more.

After excavation, the subgrade—that is, the bottom of the excavation—is carefully inspected. Soft, organic, or non-uniform areas must be replaced. The geotextile is laid on the compacted subgrade, extending at least twenty centimeters beyond the foundation area on each side and secured at the edges with ground nails or layers of stone. This is followed by the layer-by-layer placement and compaction of the frost-protection gravel. Each layer is compacted using a suitable compaction device until the required degree of compaction is achieved. A Proctor test or a load plate compression test may be used for quality assurance on larger projects.

If a concrete foundation is planned, a base course of lean concrete is placed over the gravel layer, upon which the formwork and, if necessary, the reinforcement for the strip foundation are installed. The concrete is poured, compacted, and cured until it reaches sufficient strength. Only once the concrete has reached the required strength—which can take three to seven days, depending on weather conditions—is the first layer of gabions installed and filled. The bottom layer is placed with particular care, as it sets the baseline for all subsequent layers: Any inaccuracies in the horizontal alignment and leveling of the first layer will carry over to the layers above and are nearly impossible to correct later.

Common Mistakes in Foundation Construction

One of the most common mistakes in practice is insufficient excavation depth. Those who install the gabion foundation only a few centimeters deep save time and material in the short term but risk frost damage and settlement. Another common mistake is omitting the geotextile: Without a separation layer, fine soil migrates into the gravel, reducing its drainage capacity and load-bearing capacity, and the gravel layer loses its function over the long term. Insufficient compaction of the gravel is also a classic problem: An uncompacted gravel bed settles under the weight of the gabions, leading to uneven settlement and tilting of the wall.

Especially on slopes, drainage behind the wall is often neglected. If the drainage layer is missing, slope water accumulates behind the gabion wall, increasing earth pressure and, in extreme cases, causing the structure to tip over. Finally, the frost-free depth is often underestimated, especially in regions with harsh winters. A gabion foundation that is not installed at a frost-free depth is lifted by frost heave in the soil and settles unevenly after thawing, leading to permanent deformation of the wall.

The Gabion Foundation in the Context of Sustainable Open-Space Planning

Gabion structures are considered relatively resource-efficient in landscape architecture and civil engineering because they can use local stone materials, require no energy-intensive binders, and are fully dismantlable and recyclable at the end of their service life. However, these qualities can only be fully realized if the gabion foundation is also designed to be sustainable and durable. A foundation that causes settlement damage after just a few years and requires costly remediation negates the ecological benefits of the structure.

In the context of stormwater management and infiltration planning, gravel-based gabion foundations offer an additional advantage: they are permeable and promote the infiltration of stormwater into the ground rather than diverting it over the surface. This aligns with the goals of decentralized stormwater management, as enshrined in DIN 1986-100 and in numerous municipal drainage ordinances. For open-space planners who use gabion walls in areas where infiltration is a concern, this aspect must be explicitly taken into account during foundation planning.

The quality of a gabion foundation ultimately determines whether a gabion structure will last for the intended decades or begin causing problems after just a few years. Those who understand the geotechnical fundamentals, select the right materials, plan drainage systematically, and carefully monitor construction create the conditions for a structure that fulfills its purpose durably, safely, and with minimal maintenance. This is not a given, but it can be reliably achieved with the right knowledge and the necessary care.

22.01.2025

Project

Co-creation instead of participation

Building design

Management

Participation versus co-creation: Would the Superkilen work better today if citizens had been integrated into the process from the outset?

Superkilen in Copenhagen has failed. The citizens as a whole use the square more as a place to pass through than to linger, even though they were integrated into the planning process through participation – according to a long-term analysis by students at the Danish Institute for Study Abroad. During the design and development process, the Superkilen planners asked citizens to suggest artifacts from their countries of origin for the new city square. Holistic planning with co-creation and prototypes would have been one way of increasing acceptance of the square.

Co-creation

Co-creation originally comes from the business world, which began to involve consumers in the product development process in the 1990s. The Leading Cities research group defines co-creation in urban development as “the active flow of ideas and information between five sectors: government, business, academia, non-profit organizations and citizens that promotes participation, engagement and development.”

What is the difference to citizen participation? Public participation is a means for planners to learn more about the attitudes and opinions of local residents and to develop new ideas. They increase acceptance for a project. Co-creation, on the other hand, involves the most important sectors of society on an equal footing from the outset.

It therefore offers citizens and citizens’ organizations a better opportunity to be truly heard and gain more influence in planning processes. Co-creation views users as proactive citizens rather than consumers, and focuses on long-term cultural change and the whole community rather than individual user groups. Where citizen participation seeks to integrate citizens’ opinions into an already prescribed program, co-creation helps future users to shape and enforce their own decisions. Co-creation is an endless process in the best sense of the word, with regular exchanges taking place between those involved.

Co-creation has a number of advantages. The public provides input and feels equal, citizens feel they are taken seriously. They become much more aware of their living environment. In return, the government has to be much more responsive and responsive to citizens and other sectors. In return, however, it saves costs because only what is actually needed and used is implemented and the risk of a new project is correspondingly low.

Prototypes

In large design projects such as Superkilen, it is extremely important to test ideas in advance before they become a permanent part of the landscape or city. It is a long way from the abstract idea, analysis and public participation to the concrete installation. The prototype should be seen as a learning tool that can be optimized and changed in the next step. Prototypes are a democratic way of dealing with public space, they also reduce the risk of a failed project and unnecessary expenditure.

The holistic approach

Combining co-creation with the prototyping approach makes it easier to explore the potential of a space. This holistic approach leads to more sustainable and vibrant places in the city. However, the Superkilen started with an assumption that co-creation and prototyping would have led to a different design. Users would accept the space better and make it more their own. Perhaps a more critical examination of the initial idea would also have been achieved.

You can read Bianca Hermannsen’s current analysis of the square here.
Robert Schäfer visited Superkilen in 2012, directly after the opening. You can read his review of the new city square in Copenhagen here.
Watch the video here to see how BIG travels with local residents to their countries of origin to select artifacts for Superkilen.

19.12.2024

Design

Heavyweight with a message

Building design

The Globo Uovo sculpture is an impressive work by stone sculptor Marc Reist and is currently on display at the Dürrenmatt Center in Neuchâtel, Switzerland. The artist made the 6.5-ton “global egg” out of white marble. In an interview with STEIN, the Swiss artist explains what message he wants to convey with his sculpture, why he only uses white marble and […]

The Globo Uovo sculpture is an impressive work bystone sculptorMarc Reist and is currently on display at the Dürrenmatt Center in Neuchâtel, Switzerland. The artist made the 6.5-ton “global egg” out of white marble. In an interview with STEIN, the Swiss artist explains the message hewants to conveywith hissculpture, why he only works with white stone and why he launched an appeal to collect eggshells before the opening.

Marc Reist: It’s a logical consequence of my artistic work and how I reflect on my surroundings by observing them. I notice how certain rules and mechanisms are similar on both a small and large scale. I never consciously came up with the topic, it just developed. I think it started in 2005.

The Globo Uovo symbolizes the world and the origin of life. Was there a specific reason for this idea?

Yes, that was in 2011. I was invited by a newspaper in Switzerland to write a few columns. I started to write about resources and food in these texts and about what bothers me: the way we deal with food, the way we deal with our environment. And during this phase, I designed the globe and then the egg. The eggs actually always resonate with me. Regularly for my wife – I only mention this in passing – for her birthday, for Mother’s Day, there are always drawings of chicken and egg. I either start with the chicken or the egg, but the egg always resonates.

Do the many openings in the sculpture also have a meaning?

The openings were created by the lines of longitude and latitude. And I found them very special as soon as I was able to work in the egg. There is a feeling of protection when you are in your human egg and you can see the outside world through these openings. At the same time, it could also be a prison. These feelings arose in me when I was working in the egg.

From a professional point of view – I trained as a stone sculptor and also took the master craftsman’s examination – I know almost all the materials. But even so, I used to only work with black stone for my shapes. And now, for years, I’ve only been working in white. For the small sculptures I make, I use a bright white marble. There is no other solution for me and for my forms. I have never used any materials with textures. They are beautiful, but not for my shapes.

But the marble for the egg has a certain texture. Was a block of 55 tons in pure white not available?

For the Globo Uovo, the stone is a little more marbled. Because this size in pure white – that would have been almost impossible and would have meant such a long wait. And the egg in this size in pure white would almost be a little too beautiful(laughs), almost baroque. That’s impossible. Visually too, it’s almost not rock anymore.

So the egg also looks much more “alive”.

Exactly, that’s what I mean. This methamorphosis of the rock, this mountain, that has to resonate.

How did the change from black to white rock come about?

That’s an interesting question. I have to go back to that. I wanted to make a really big sculpture in the 1990s. I chose a large block in Carrara without knowing what I was going to do with it. I wanted to be inspired by the material, by the block. I normally proceed differently. I have a drawing or a model and then work on the stone. But now I wanted to be influenced by the block. At the time, it was 20 tons in size. And that put an enormous strain on me(laughs). I suddenly realized that the further north the block was transported from Italy, the greater the strain in my head became. I was very blocked! And suddenly I found the solution. I then worked out a light cloth from this block. That was probably my solution, to release this heaviness in me in relation to the block. And since then I’ve only worked with white stone.

Are there purely visual reasons why you like to work with marble a lot, or is it also because of its properties?

Both, actually. My sculptures are also a matter of light. Not only with the large egg, but also with the other sculptures. The way the light passes through the opening and the edges is what makes it so good. And the properties for working are a pleasant side effect. It is easy to work with because it is so even, so homogeneous. But I mainly use marble because light and shadow are important for my sculptures.

You also want to send out a message with your art objects.

Yes, absolutely. I think that’s the greatest task of an artist. That his work is seen and heard, as the case may be. Communication is important. It makes no sense at all if I make an egg like this just to have another beautiful sculpture in a park somewhere. That wouldn’t be enough. It needs a message.

What message is that?

We have great difficulties with resources in general. This is most sensitive when it comes to food. And I really want to draw attention to the fact that people need to deal with the issue of food and resources. That a small train of thought changes.

Your sculpture is currently on display at the Dürrenmatt Center in Neuchâtel, Switzerland. Before the exhibition began, you launched an appeal to collect eggshells. What was the reason?

We had planned a performance with a dancer for the vernissage. I needed a lot of eggshells for that. Over the course of a year, people collected around 35,000 eggshells, washed them and brought them to me. Something you would normally throw away. For the exhibition opening, we laid them out on the floor of the museum and cleared paths, like a labyrinth. The dancer danced her way through it. But every now and then she made missteps on the eggshells, causing them to crack. And at the same time, with every misstep, a part of her body died. Because the shells represent our resources and if they are destroyed, the person dies too. And so she danced through the labyrinth and gradually died a dramatic death after three or four missteps.

Find out more about the project and the natural stone work in the February issue of STEIN. You can also find more information at www.stein-magazin.de/skulptur-des-monats-globo-uovo.