Gabion baskets are wire cages filled with rocks, concrete, or other natural materials. They are used in landscaping and civil engineering projects for erosion control, slope stabilization, and retaining walls. Gabion baskets are a popular choice due to their durability and low maintenance requirements.
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In landscaping, gabion baskets can be used to create raised beds, retaining walls, and even outdoor furniture. They can also be used to create water features such as fish ponds or waterfalls. Gabion baskets are often used in areas prone to erosion or in need of slope stabilization. In addition to their practical uses, gabion baskets can also add a unique and visually appealing element to any landscape design.
There are a few different options for filling gabion baskets. The most common choice is rocks, which can be easily sourced from a local quarry or riverbed. Concrete can also be used, although natural materials are generally more environmentally friendly. Other options for filling gabion baskets include wood chips, recycled glass, and even plants.
When used in landscaping and civil engineering projects, gabion baskets provide both functional and aesthetic benefits. They are a durable and customizable option that can be tailored to fit the specific needs of each project. If you're considering using gabion baskets in your next project, be sure to consider their versatility and strength as a building material.
Gabion baskets can certainly be used for retaining walls. In fact, they are a popular choice for retaining wall projects due to their durability and versatility.
Retaining walls are structures that are used to hold back soil or other materials on a slope. They are commonly used to create level areas in yards with sloping terrain, or to prevent erosion in areas prone to landslides. Gabion baskets are well-suited for retaining wall projects because they are strong and can be easily filled with a variety of materials.
One of the main benefits of using gabion baskets for retaining walls is their durability. The wire baskets provide a strong framework, and the filling material adds even more strength and stability. Gabion baskets are also relatively low maintenance, as the filling material does not require any special care.
When it comes to designing a retaining wall using gabion baskets, there are several factors to consider. The size and shape of the baskets will depend on the specific needs of the project, as well as the material being used to fill the baskets. It's important to work with a professional to ensure that the retaining wall is properly engineered and built to code.
The best way to calculate how much rock you will need is to calculate the area of the basket. Do this by multiplying the length by the height by the depth. For example: How much rock do I need if my gabion basket package is 5m long, 1m high x 0.5m deep?
5m x 1m x 0.5m = 2.5 cubic metres of rock.
Landscape supply yards and other rock supplies will generally sell rock in the cubic metre (m3). Often 1 bucket load from their loader is 1m3 so this makes it easy to determine the correct cubic meterage required. We've helped save you time by calculating the rock required for a range of common sized baskets. Simply multiply the value by your wall length to get your total cubic metre rock required. See the table here
This is important to ensure your rock doesn’t fall through the aperture (mesh opening) of the basket. Using our 50x50mm mesh means your rock size can be smaller than using a larger mesh of 75x75mm or 100x50mm. The challenge with larger mesh is that you require larger rock which can often create large gaps between the rock. This exposes more openings and within the basket which is aesthetically displeasing.
The mesh opening is 50x50mm. This means that any rock smaller than 45mm or 50mm in diameter will fall through the wire mesh. Based on the aperture above, the recommended rock size is a minimum of 70mm stone. Normal size rock would be 70-150mm
We offer both a galvanized or a galfan coating on all our range. Both coatings are widely accepted globally as suitable coatings for corrosion resistance in outdoor applications.
Galvanised steel products have been around for hundreds of years. The process of galvanising is believed to have been discovered in India in the 4th century AD and was later discovered by Europeans in the 17th century when it had been used as armour for Indian armies. These days, galvanised steel is everywhere. Most commonly used in the construction industry, galvanised products include support beams, piping, heating and air conditioning duct work, barriers and handrails. Galvanized steel is used to make outdoor grates used for industrial walkways street lights, beds, washtubs, buckets, nails, planter boxes and of course, gabion baskets.
Galvanisation is the process of applying a protective zinc coating to steel, to prevent rusting. The most common method is hot-dip galvanizing, in which parts are submerged in a bath of molten zinc. Galvanizing protects in two ways.
Source: Wikipedia
Galfan is zinc-aluminum alloy coating as compared to a pure zinc coating (galvanized). It is generally 95% zinc, with 5% aluminum alloy and mischmetal steel. Galfan offers an excellent level of protection against long term corrosion as the corrosion rate is closer to a parabolic shape rather than linear as per a galvanized finish.
The type of finish most recommended is dependent on the location and expected life span of the project.
If you're going to the effort of building a retaining wall, feature wall, water feature or even letterbox using a rock filled gabion basket, you want to know it's going to last. After all, this is going to be a feature of your outdoor area and if you're going to do it, you might as well do it right.
One of the most basic but crucial aspects of your gabion basket is making sure the rock / stone you are going to fill it with, actually stays in the basket. Here's what I mean: The baskets by design are a steel mesh in grid form, therefore there are consistent gaps between the steel cross beams. The gaps between the mesh wire of the gabion basket is called it's aperture.
The gap between the steel cross beams of wire mesh vary from manufacturer to manufacturer in both shapes and sizes. Some manufacturers promote the use of chicken wire style. There are 2 problems with this:
The thin, low gauge steel wire is very easy to move and bend. This means is that rock filling can manoeuvre the wire. Alarm bells should be going off for you right now. The rock filling can manoeuvre the wire! This means the rock inside the basket can move, stretching the wire, creating weak spots and ultimately creating an inconsistent aperture throughout the basket. An inconsistent aperture now means that there is potential for rock filling to start spilling out of the basket. What a disaster...
The alternative is a strong, high gauge (4 or 5mm) steel basket with a consistent, square aperture. This is what we offer at Gabion Walls Australia.
One of the most critical aspects of installing a gabion retaining wall, rock wall or landscape feature is ensuring the rock filling is packed inside the basket as effectively as possible.
Different types of rock filling requires slightly different techniques. For example, stone of a flatish nature will pack to a denser finish than rounded pebbles or river rocks. Flatter stones will give you a traditional dry stacked effect in your basket as opposed to a rounded river rock that will which will give a more freeform jumbled look.
If using a river rock or rounded stone ensure that the stones are placed and stable before continuing on to the next layer, rounded stones tend to compress under weight (as they are only touching each other at a few points) and you could end up with some bellowing out at the centre points. This will often happen if you just pour the stones in.
Sedimentary stone, like Castlemaine Stone, tend to have grains or layers within them, this allows for splitting or fracturing to give a flatter surface and therefore greater areas of contact between stones. This allows for smaller gaps and a denser finish to the wall of the gabion basket. Once placed into position there is very little chance for movement of the stone.
Watch the video on installing rock in your gabion basket
Permit rules are domain of local councils and often change from council to council and state to state.
VIC
In Victoria any retaining wall less than 1m in height is exempt from a building permit unless it is associated with other building work or with protection of an adjoining property.
Please check with your local council for specific requirements and the Victorian Building Authority for more information:
https://www.vba.vic.gov.au/__data/assets/pdf_file///435e072fb618dc9b0b90e67b72c4df.pdf
NSW
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Generally in NSW you do not need council approval if your retaining wall is:
Please check with your local council for specific requirements and the NSW governing body for more information:
https://www.lawaccess.nsw.gov.au/Pages/representing/lawassist_fences/retaining_walls/approval.aspx
QLD
In Queensland, building regulations advise you will not need building approval for a retaining wall if:
Please check with your local council for specific requirements and the NSW governing body for more information:
https://www.brisbane.qld.gov.au/planning-and-building/do-i-need-approval/residential-projects/yards-pools-fences-and-landscaping/build-a-retaining-wall
Gabion baskets are designed to last an a long time in outdoor, adverse conditions. The rate at which the gabion basket will corrode is dependent on a large number of factors including:
One of the main factors that affects the longevity of gabion baskets is the filling material. Natural materials like rocks tend to be more durable and have a longer lifespan than concrete. They are also less prone to cracking or breaking over time.
Proper installation and maintenance are also key to extending the lifespan of gabion baskets. It's important to follow the manufacturer's instructions and consult with a professional for installation. Regular maintenance such as checking for damage and refilling gaps in the filling material can also help extend the life of gabion baskets.
The Atmospheric Corrosivity Zones in Australia (AS :) defines 6 categories of corrosivity:
Category Corrosivity Typical Environment Expected Life Span C1 Very Low Dry Indoors 100+ years C2 Low Arid / Urban inland 100+ years C3 Medium Coastal / Light industrial 50+ years C4 High Seashore (calm) 30+ years C5 Very High Seashore (surf) 15+ years CX Extreme Shoreline (severe surf) 5+ yearsOnce you have decided what size gabion basket you need to complete your retaining wall, rock wall or landscape masterpiece, you have the option of picking it up or delivered. All baskets are available in flat pack form or pre-assembled.
Pre-assembled baskets save time for a quick installation however the flat pack form and building yourself is easy and the most cost effective solution. As the gabions are so easy to put together, our recommendation is to build and place in final resting location when on site.
Approximately 40 baskets can be stacked in flatpack form on a single pallet (totalling approximately 1m high). As you can expect, this is more effective way of transporting the baskets compared to picking them up pre-built due to sheer shipping volume.
Our house is situated at the top of a hill and the driveway slopes down towards the house. With no off-street parking due to the single track lane, we only had a small area of old, sloping crazy paving to park our two cars. Every time you opened a door it would swing into something – usually a leg or another door!
We did, however, have a grassy area to the side of the driveway, which would be the ideal spot to extend the driveway and build a garage. However, the bank would need a serious retaining wall.
So, what type of retaining wall should we build?
The first option, which I’m sure lots of people investigate, is a dense block wall or a hollow block wall reinforced with rebar and concrete. However, a structural engineer would need to get involved due to the height we required, plus we knew that the finish in brick would be costly. Render wasn’t an option as it would need regular maintenance due to the damp conditions.
We spoke to several builders, but quotes came back between £10,000-20,000 (!) for the 2m high by 20m wide retaining wall.
I knew I could do something for less and a gabion retaining wall system was the answer. We had plenty of brick rubble leftover from our internal house renovations which could fill the gabions. We also had the space to accommodate the 1m deep baskets, leaving us with about 8m of useable driveway.
I decided to buy the gabions from gabionbaskets.co.uk (or Fine Mesh Metals is their other name). They have lots of choice, great installation information and lots of case studies to look at.
A common question is how long do gabions last? I discovered that the ones from gabionbaskets.co.uk are Galfan coated which means they last 4 times longer than standard galvanised baskets. So make sure you check for this as some of the cheaper ones available are only galvanised with no extra treatment.
I mocked up our gabion wall design in excel and sent it over to gabionbaskets.co.uk who were able to work out a cost for me. This included a strengthened 4mm front face on each gabion (to help reduce any bulge), the lacing wire, partition panels for the decorative stone and helicoils for easy front joins. The helicoils are more noticeable than the lacing wire, but I think add a nice, framed look to each basket.
As with any DIY project, the planning and site preparation are the most important steps in the whole process. We hired a man and his digger to remove the tree stumps and cut back into the bank along the line of our boundary. All the top soil was removed until we reached firm, solid ground. The gabion foundation can be a layer of compacted hardcore 100-200mm deep. Or in our case we had reached a flint and chalk layer which was solid enough.
Using a spirit level (or app on a mobile ), I made sure the ground was level left to right, but also angling 5-6 degrees leaning into the bank. Gabion baskets must lean slightly backwards to aid their retaining powers.
Next, I put down a sheet of woven geotextile to stabilise the ground and added a thin layer of gravel to help find the final angle of 5-6 degrees into the bank.
As with any retaining wall, you need to consider how to alleviate the build up of pressure caused by excess water in the retained soil. Strictly speaking, as the gabion basket method is completely porous, you might want to skip this step, but it doesn’t hurt to add extra drainage behind the baskets if you can.
I achieved this by adding an 80mm perforated drainage pipe along the back of the bottom row, sloping slightly in the direction I wanted it to drain. The pipe was wrapped in a non-woven geotextile and topped with a good 300-400mm of gravel, similarly to what you would do for a French drain or behind another type of retaining wall.
The cheapest way to fill a gabion basket is with gabion stone bulk bags. I found a great selection at Mainland Aggregates. Gabion stone is just another name for angular limestone. The fancier the colour the more expensive they get, so stick with plain old Buff or York gabion stone. These can be hand placed along the face of the basket.
Unfortunately, after trying out the gabion stone, it didn’t feel modern enough for our residential setting. It looked more like that seen at industrial sites or on the side of a motorway!
Scottish cobbles, on the otherhand, would provide a more modern look to the retaining wall. However, they are very expensive! One bulk bag doesn’t even fill a 1m3 basket. So, to reduce costs, I used a partition panel set back 100mm from the front of the basket along with the 80-120mm Scottish cobbles.
Using the cobbles and panel also meant I could use recycled stone as the in-fill, which was even cheaper than the gabion stone. We had lots of rubble leftover from our internal house renovations, which was perfect for filling up the baskets. I also ordered more recycled brick from Mainland Aggregates to finish the job.
Bracing the gabion basket is a step that cannot be skipped as it reduces any gabion bulge.
The lacing wire was cut into approx. 1.5m lengths, then threaded through the same place in each gabion, eg 4 spaces up, 4 spaces from the left, 4 spaces up, 4 spaces from the right etc. I then looped the wire back through the way it came, and twisted the wire around itself in the middle of the basket to prevent it coming loose. A set of pliers was used to grip the middle of the wire and twist it to make it taught.
It’s important to do this both ways, though I have to say I did fewer side to side, it was the front and back ones that were the most important to stop the bulge on the front face.
As our retaining wall was 2m high it required a second layer. This layer can step back a little into the bank, or, as in our case, the fronts of the baskets were kept in line.
Remember to make sure the baskets on the bottom row are filled right to the top before adding the second layer. Otherwise, the weight of the material in the top baskets will sink down into the bottom layer and misshape the lid.
I also laced the lids shut before adding the next row. When attaching the front helicoil, this must be woven into the lid of the bottom basket and the base of the top basket so that they are completely joined together. Top and bottom layers must be laced together on all sides with the lacing wire, so again the whole section is ‘as one’.
With regards to finishing off the gabions, make sure that all sides are laced together and the lids are secured with the helicoils. I didn’t in the end fill the tops with cobbles. They were a leaf trap in the Autumn, and it was difficult to fish debris out. At some point, I plan to lay more white non-woven geotextile over the top with a thin layer of soil and grow rockery type plants near the edge so that they drape over in time.
Here is our finished gabion retaining wall!
I hope you’ve found this useful. Please feel free to leave any questions in the comments and I’ll do my best to answer them. Remember we’re just DIY’ers doing it our way in our set of circumstances. Please seek professional advice for your own retaining wall project.
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