I know this is off-topic. But this was a cherished personal project of mine and I think it’s worth sharing. Plus it’s a great DIY project – many of you here are DIY enthusiasts! 🙂

I’m excited to present a unique project I’ve undertaken, something that’s quite rare, especially in Europe — a robust tire retaining wall crafted from 530 recycled tires, each manually packed with approximately 212 metric tonnes of earth. That’s right, 530 tires! I’ve devoted countless hours to ramming dirt into each tire, working tirelessly until my hands and shoulders could take no more, only to happily resume the task the following weekend. 😎💪

Get ready, this is a long read! I tried to include as much useful information as I deemed useful for anyone thinking about doing a similar project. But you could just check the images and read the most important sections :).

If you prefer a shorter run-through, check out my video:

This project epitomizes the classic trade-off: saving a significant amount of money while investing considerable time and effort. As someone whose primary occupation involves sitting behind a laptop, engaging in this kind of manual labor was not just a welcome change but also immensely satisfying. It’s true what they say — you can take the boy out of the village, but you can never take the village out of the boy!

Moreover, it was an excellent opportunity for quality bonding with family and friends. A special shoutout to my brother, who was by my side, working tirelessly. His dedication was indispensable, and without him, this project would have taken twice as long. Our time together was filled with hard work, laughter, plenty of beers, great music, and memorable conversations and stories.

The challenge was to build a 30m (98ft) long and 1.2m up to 3.5m (4ft up to 11.5ft) tall wall that also bent behind the corner of the hill (90°) another 5m (16ft). The slope was gradual, but this was still a big retaining wall.

What were the traditional options?

I have considered several options and received quotes for them. To give you a reference point for the quotes, let’s put things into perspective first:

The entire container house with the massive veranda, a solar panel with batteries that power all LED lights, sockets, and a fridge cost me about $18,000. Including hauling the shipping container on a lorry about 80km, pulling it up the hill with a tractor, and placing it in place with a crane. And all the other work that went into it to make it feel cozy.

But, it was worth the effort — this is now a place of peace, an island of serenity, away from the world and its stress, politics, hustle culture…

I hope you now get the idea that I am doing this very low-cost and DIY. So forking out any big amounts that are out of proportion to the entire project is not going to work here.

With that in mind, here are the traditional options:

• a concrete retaining wall — this would involve a huge amount of concrete and steel, heavy lorries hauling all the stuff from about 20km away, and renting all the shuttering, which would cost me about $15,000. Plus, this would be ugly — a massive concrete slab that would look more and more battered over time. I didn’t want that.
• gabions —steel wire cages filled with rocks — a gabion is a large cage, cylinder, or box filled with rocks, used for erosion control, slope stabilization, and fortifications. Now I do like the look of those, but these would cost me upwards of $17,000 (and that’s just an estimate, the real cost would be even higher).
• cinder blocks — about as expensive as a concrete wall… and about as ugly as a concrete wall.

On top of all the negatives of these traditional options, there’s also one important one to me: I like spending time at my cottage, with friends and/or family. I like the manual work on the wall as my profession and most other projects require sitting behind a laptop. I like to have a good beer and a BBQ after a day of hard work in the sun.

If I had a company build a concrete wall for me, or even if I did it myself, it would be finished in a few weekends. It would just be another job.

This wasn’t a job, it was an experience. And guess what we should spend more time on in life ;).

Bring on the tires!

I came across tire retaining walls mostly when backpacking across South America — they were used there a lot, perhaps not as much for tall retaining walls, but for a lot of similar purposes. Then, there are the famous Earthships that utilize tires a lot.

I am also a fan of recycling and working with what you have instead of manufacturing new stuff.

That’s why I thought:

“hey, how about building the wall out of tires! I wonder what would that entail.”

I spoke to a few people about it first, and they were skeptical — mostly saying that the tires won’t hold.

But hey, I’m a stubborn bugger ain’t I.

I decided to research the hell out of it and discovered numerous large-scale tire retaining walls, many surpassing the size of what I had initially envisioned. My exploration revealed various techniques for connecting and reinforcing the tires, ensuring they were structurally sound and not merely reliant on the weight of the earth and friction to stay in place.

Armed with this newfound knowledge — understanding that a well-constructed tire retaining wall can support significant weight when built with structural integrity in mind — and considering the steep costs of alternative solutions, my decision was clear. This was the path I was going to take.

We’re building a tire retaining wall.

Procuring the tires

Getting the tires is easy — all you need is to ask — many car services will give you tires for free, you just need to pay for the transport. Many local places used tires for something, but don’t need them anymore — they will be happy for you to take them.

That’s how I ended with the first batch of 150 tires and great enthusiasm to start. We waited until the dirt dried out a bit after winter and the work started.

How long did it take?

In my initial calculations (without knowing how much are the tires going to stretch when filled in and what size tires we are going to get) I calculated that we needed around 750 tires. We ended up using 530 tires (phew!).

I didn’t have any idea how much work is needed to properly fill one tire with dirt and pound it solid, but I estimated this is going to take longer than one summer to finish.

The project spanned from approximately April 2022 to the first weekend of November 2023, with our efforts concentrated mostly on weekends. We were at the mercy of the weather, only able to work when the earth was sufficiently dry; thus, any weekend dampened by rain meant a pause in our progress. Our commitment to the project was balanced with the rhythms of life — we took breaks for holidays, family events, and trips. During the summer months, we (or me alone) occasionally worked weekdays as well. I didn’t meticulously record the total number of days dedicated to the project, so I can’t provide an exact count.

But a rough estimate is about 53 days. More on that below, section How much work is it?

Get a solid and flat foundation

Keeping the low-cost element in mind, all that was needed was to dig a ditch for the first row of tires (as opposed to a concrete foundation). I wanted them to sit in something solid, the dirt there was tough and clay-rich. (If you don’t care as much about saving money, you could lay a concrete foundation — but I think it isn’t needed anyway).

It helps to start with a solid first row that is level and the tires don’t have any bumps — as any bump here could cause trouble later on. But— one benefit of building with tires is that they are not bricks — they are rubber after all. They can be filled less if a lower level is needed, or you can fill & pound them with more dirt to fill more vertically.

At first, we started laying them using a spirit level, but as we went along, we realized this wasn’t necessary. Each row of tires can be adjusted, each tire can be adjusted for height or even width (you can compress or stretch the tire, and fix it in place with screws, more on that later).

Structural integrity

The purpose of a retaining wall is to effectively hold back heavy soil and water. It’s crucial to consider that soil can significantly increase in weight post-rainfall, a factor that might not be intuitively grasped in typical DIY projects.

To navigate these challenges, you have two paths: delve into the technicalities of calculating the pressure exerted by wet soil on the tires at varying wall heights, considering soil type and anticipated rainfall; or alternatively, gather insights from YouTube tutorials, consult with knowledgeable individuals, examine other tire retaining wall projects for their approaches, and then craft a plan based on this research.

Guess which approach I chose? 🙂

The latter of course! Since this isn’t a retaining wall that needs to hold a road in place, I suppose I can afford some creative license.

I took the middle road — most of the projects I saw online built tire retaining walls that were less structurally sound than what I decided to build and most of the other projects — concrete retaining walls and similar — were much more structurally sound (but they were created by engineers for big projects with more responsibility and risks, higher load).

Here’s how we made this retaining wall structurally sound(-er)

• solid foundation — the first row is sitting in a solid ditch — leaning against hard clay soil that won’t budge
• interlocking/friction —each tire is fastened to its adjacent counterparts using wood screws, ensuring three-way reinforcement — both sides and three screws into the tire beneath. This method not only augments the friction necessary to resist movement from the soil it’s holding back, thereby reducing the impact of lateral soil pressure, but it also stabilizes each tire during the filling and compacting process. This technique simplifies the task considerably, as it allows for the arrangement of a complete row of empty tires first, which can then be filled progressively. This approach opens up the possibility for a division of labor, where one team can focus on securing the tires while another fills them, streamlining the entire process.

• strengthened bottom part — the bottom 5 rows of the wall (where the soil pressure tends to be highest) are held in place with a 1cm (0.4 inches) iron bar every 2 meters (2.2 yards). These bars are driven (pounded) about 0.5m (1.6 feet) into the ground
• angle of repose (incline towards the slope it’s supporting) — each row of tires is offset by about 10–20cmcm (3.9 to 7.8 inches) — more at the bottom, less towards the top, which makes the wall lean strongly against the soil it is retaining (at about 70 degrees angle/tilt). This means that the soil behind would need to generate several times higher pressure than usual to tilt the wall over.
• natural/long-term interlocking and erosion prevention— I have planted a cotoneaster into almost every tire — it’s a crawler that grows close to the soil and roots wherever it touches the ground. It will grow through the tires and connect each one with its branches and roots — securing the whole thing further and turning the tire wall into a green wall in about a year. And it doesn’t grow too big so its roots won’t damage the tires.
• the wall is L shaped — giving it additional strength and support, like a buttress or counterbalance to the soil’s lateral pressure

This was the finishing touch, planting cotoneaster, and lavender in the top row, early November

• drainage — I have ensured good drainage of the soil behind the tires (most of the land is under a roof, effectively minimizing direct water accumulation, and any excess water is taken away by underground drain pipes)

Plus the usual good attributes of a tire wall:

• wall drainage — any remaining water doesn’t accumulate behind the wall as it would with concrete. Instead, it flows freely through the tire wall, reducing pressure buildup.
• flexibility — it’s rubber — it is flexible, can move and it won’t crack. It was put to the test a month after it was finished by a magnitude 5 earthquake with an epicenter only about 10km from the wall.
• weight — each tire contains about 4 wheelbarrows of heavily pounded and compacted dirt (one wheelbarrow is ~2.2 cubic feet (0.06 cubic meters) — I have an old school smaller wheelbarrow) of soil inside, with some rocks. One wheelbarrow of soil is about 230 lb (100 kg)*4 = 920 lb or 400kg of dirt per tire.
  That makes 530*400kg = 212 tonnes of soil. We can add the weight of all tires too — 530 * 9kg (single tire weight) = ~4.8 tonnes. And 18kg of the ~2500 copper screws… 🙂
  Giving us a total weight of 217 tonnes (239 US tons). (Shit, did we just manually shovel, wheelbarrow, and pound 217 tonnes of dirt? Oh yes we did!)
• friction between rubber tires — even moving an empty tire over another is challenging. Now imagine attempting this with a tire filled with 400 kg of dirt.
• the soil at the base of the wall isn’t newly added but part of the existing hill, making it more compact and stable. This means only about half of the wall’s height is actually retaining new soil.
• the wall’s height varies, starting at 1.25 meters and gradually rising to 3.5 meters. This slope means that only certain sections of the wall are subjected to maximum pressure, occurring at the tallest point.

Here’s what ChatGPT (the most advanced AI model) has to say about it:

To estimate the weight of soil that a retaining wall can support, we need to consider the wall’s dimensions, construction, and the physics of soil pressure. Your retaining wall, made of tires filled with pounded dirt and reinforced with screws and iron bars, sounds quite sturdy. Let’s break down the calculation with the given parameters:

Wall Dimensions Foundation and Structure:

• Height: 3 meters
• Thickness: 0.5 meters
• A solid foundation in a ditch against hard clay soil enhances stability.
  Interlocking tires with wooden screws and iron bars at the bottom part significantly increase the structural integrity and resistance to lateral soil pressure.
• Angle of Repose:The wall’s incline (about 70 degrees), with each row of tires offset by 10–20 cm, adds substantial resistance to soil pressure.
• Vegetation and Drainage: Planting cotoneaster for natural interlocking and erosion prevention, combined with good drainage, helps in reducing the hydrostatic pressure and reinforces the wall.
• Flexibility and Weight: The flexibility of the rubber and the substantial weight of the wall (217 tonnes from dirt and 4.8 tonnes from tires) contribute to its ability to withstand soil pressure.
• Increased Structural Integrity: The L-shape design allows for the distribution of forces more evenly across the wall. The corner where the two sections of the wall meet provides additional support and resistance against the lateral pressure of the soil.
• Counterbalancing Effect: The perpendicular section of the wall acts as a buttress, providing extra support and stability. This is especially beneficial in resisting the overturning and sliding forces exerted by the soil.

Soil Pressure Estimation:

• The lateral earth pressure on a retaining wall depends on the height of the wall and the density of the soil.
• Average dry soil density is approximately 1.6 tonnes per cubic meter.
• The lateral earth pressure (P) at the base of the wall can be estimated using the Rankine’s formula for lateral earth pressure, which is P=γh, where γ is the unit weight of the soil and ℎ is the height of the wall. However, this formula doesn’t account for the angle of repose.

Incorporating the Angle of Repose:

• The angle of repose adds an additional component of passive earth pressure, which increases the wall’s capacity to hold back soil.

Given these parameters and the complexity of calculating the exact pressure considering the angle of repose, I’ll provide an approximate calculation for the weight of the soil that this wall could support:

• Assuming Maximum Lateral Earth Pressure Without the Angle of Repose:
• At the base of the wall, for a height of 3 meters, the lateral earth pressure from the soil would be:

• Over the entire height of the wall, this pressure will vary from zero at the top to maximum at the bottom.

Given the angle of repose and the reinforced construction, the wall can likely support a higher amount of soil pressure than this basic estimate. However, for a precise calculation, especially considering the angle of repose and the reinforcing elements, an engineer would need to perform a more detailed analysis using specific geotechnical engineering formulas and methods.

Please note, these calculations are simplistic and intended for a rough estimate. They do not replace the need for a professional evaluation, especially for a structure with significant potential hazards if it were to fail.

Well, that was a handful! So with all this in mind, I can sleep calmly knowing that the wall can withstand quite a bit.

Required tools and materials

Tools

The best thing about building a tire retaining wall is that you don’t need any heavy or complicated equipment, all we used was this:

• a 1.5kg (3.3lbs) hammer
• a 15kg (33lbs) DIY tamper— you can’t buy this, my handy brother made it for us — it’s a steel pipe submerged in a plastic bucket of concrete. The bucket is then removed and you have a heavy tamper made of concrete. You could probably use a standard tamper, but a huge benefit of our one was its round shape. A square one would get caught on the tire easily (a kind of recoil…)

• double-sided hook — this is a must! It is used to lift the side of the tire and allow you to pound the dirt underneath — creating a much more compact pounded tire than without it. We made it out of two standard hardware shop aluminium hooks.
  • or you could use a pickaxe to lift the sides of the tire — it’s a bit heavier to move around, but it should be easier on your back as you’re leaning towards the pickaxe handle with your body weight instead of pulling upwards with the hook. See how in this video.

• a power drill
• two shovels
• a pickaxe + this might be useful too — we created a kind of a cross between a pickaxe and a chisel — easier to chisel down the side of a slope, easier on your back too. It’s the pickaxe, but vertical, stuck in steel pipe:

• a wheelbarrow
• a spirit level — we used it a lot at the beginning, then we stopped as it was slowing us down and the tires were quite flexible and malleable.
• gloves — particularly when handling the tamper! Even if your hands are as tough as old leather, this beast of a tool can cause calluses unlike any you’ve experienced before.
• marking string — we used it to keep the tires nicely in line. You won’t need it if you are following the contours of the slope.

Materials

• about 2500 wood screws(threaded fasteners)— the majority were 5cm (2 inches) long and 0.5cm (0.2 inches) thick, we also used some triple as long where needed. I strongly recommend the Torx type, they hold on the power drill bit much better. Saves your back!
• tires! 😀
• a lot of soil — as mentioned above, each tire will take about 4 wheelbarrows (depending on the size of the wheelbarrow, the size of the tire, and how much is the soil compacted).
• flat rocks — to place as a plug when two tires overlap and create a hole for the soil to escape through.
• iron bars — the more you put in, the sturdier and sounder the wall will be
• I also destroyed about 3 pairs of shorts and 4 T-shirts. They basically disintegrated under the stress of all the sweat, sun, and wear and tear…

How much work is it?

Glad you asked! As everyone’s wall will have a different number of tires, I will give you an idea of how many tires you can do per day, or how much time you need for one tire. It all depends on these factors:

• the size of the tire — a 185/65/r14 will take less soil and work than a 235/80/r17
• what tools you will use — we used a tamper, hook, and hammer. Others use their feed and a sledgehammer. The time to finish one tire will change with the tools you use.
• how many people work with you — for the initial 180 tires, it was mostly a two-person effort, I did about 100 tires on my own. The final stretch involved mostly a team of four, which proved to be highly efficient: two focused on securing the empty tires, while the other two handled the filling. Since attaching the empty tires is a quicker task, those team members were able to assist with the filling once their primary job was done. This allowed for a smooth rotation between compacting the soil with tampers and hammers.

With this setup, we managed to dedicate around 3 hours each day to pure hardcore work per day. This might seem modest, but the physical demands of pounding and hammering are exceptionally strenuous (it’s truly tire-ing, pun intended! 😊). While other tasks like positioning the tires, screwing them together, filling them with dirt, and shoveling were comparatively less demanding, they all hinged on the completion of the tire compaction.

To manage the workload and the summer heat of 35 degrees Celsius (95 F), especially under direct sunlight, we adopted a rhythm of 30-minute ‘sprints’ of work followed by 20-minute breaks. These intervals were crucial not only for coping with the physical challenge but also for staying safe and efficient in the heat.

3hrs of pure hard work + 2hrs of standard breaks + 2hrs for cooking and eating lunch + 2hrs for other jobs around the tires + going for a swim sometimes, finishing at around 19:00 for the BBQ is just about all you can fit in a day without exerting yourself unnecessarily. But don’t let me stop you — if you can work 8hrs, go for it :).

Our goal was to also enjoy the experience: taking in the beautiful views and scenery, sharing stories, and enjoying a cold beer together. We maintained a good balance. After all, there’s no sense in completely exhausting ourselves — it’s not a gulag!

With this rhythm, a team of two could compact about 8 tires per day to a very dense consistency, essential for the bottom layer. If working solo, one could manage to compact 4–5 of such tires daily. As we progressed, the efficiency increased, allowing two people to handle 10–13 tires per day in the later stages.

These figures are approximations based on our experience. In the first year, we completed around 180 tires, primarily with two people working. Nearing the project’s completion, our knowledge, tricks, and hence productivity soared, with a team of four nearly completing 200 tires in a single month.

Let’s take an average of 10 tires per day for the sake of easy calculation:

530 tires / 10 = 53 days

How to pound the soil into the tires

You can see the process better in my “How to make a tire retaining wall” video too.

As the project progressed, we continually refined our methods. Initially, we employed a range of tools and techniques to ensure highly precise work and denser packing of the tires. Over time, we adapted and streamlined our processes for greater efficiency. Notably, the tires near the top of the wall were not packed as densely as those at the bottom.

Each person embarking on a similar project will undoubtedly discover their unique approach. While you may find even more effective strategies, here’s a glimpse into what worked effectively for us:

• We first placed the entire row of empty tires and screwed them in. We used a marking line to keep them in line, initially also a spirit level, but stopped later on as it wasn’t needed.
• We then filled each tire with dirt, piling it up, covering the entire tire
• The soil was then pounded and compressed using the tamper (you’d be surprised that a tire that is overflowing with soil suddenly appears empty when the soil is compressed)
• Repeat (pile the tire up with dirt again, pound it down again)
• You should have the tire about 70% full and the soil should be pretty dense from the tamper, especially in the center
• Now fill it up a bit, not as much as before
• Hit the dirt from the center of the tire towards its sides — push it under the sidewall of the tire, lifting the sidewall with the double hook, so more soil enters. Hit it hard — it can take a lot
• Ensure that the tire is solid and densely packed. When you press down on its side, it should barely yield and feel firm under your touch. A less dense tire will weaken over time as the soil settles, transforming a soft tire into an even softer one. In contrast, a tire packed densely will only become slightly less dense, maintaining more of its structural integrity.
• On to the next one, only 529 to go!
• It helps to have more people working and use division of labor — each person does a specific job and things move along smoothly:

Make sure you enjoy yourselves — it is hard work, but it can be good fun at the same time. Look, everyone is happy at the end, despite the calluses!

How much did it cost?

• $350 — digger
• $380 — materials — screws, iron bars, gloves, etc
• $980 — trolley (although this will serve for years to come, so not a one-off cost)
• $500 — fuel, tire delivery (before I bought a trolley)
• $450 — food + drinks for friends and family helping out

TOTAL: $2,660 (some of these costs would still happen with any other option too)

Beats $15,000 and more for the traditional options — my $13,000 saving calculation takes into account that the “traditional retaining wall options” calculation at the beginning is rough and doesn’t take into account all the accompanying work that would need to be done.

Recommendations (that will save you time and nerves!)

• Use low profile tires as much as you can — it’s easier to pound the dirt in them as the opening is bigger, no need to use the hook (as much) or kick the dirt in

• When hammering the soil into the tire — use the hammer sideways too. It will push more soil inside, you can pound it solid at the end with the normal side of the hammer.

• Don’t worry about leveling (spirit level). Or perhaps do it at the beginning, to get a good leveled start but not for every row as the tires are malleable and stretch depending on how much you pound the soil in them.
• Try to use as many as possible of the same tire size, for example, a 195/16/r15 — this way you can stagger each row more easily. But even similar tire sizes work too.
• Thoroughly compact the soil inside each tire until it’s as solid as rock. From my observations in numerous videos, many people simply tread on the soil or give it a light hammering — this approach doesn’t suffice for a tall retaining wall. Such a method might be adequate for a cosmetic or partition wall, but for structural stability, every tire must be tightly packed. Keep in mind that soil tends to settle over time. Therefore, the softer it is initially, the more likely your wall will slump and lose its integrity over time.
• Stockpile a selection of wide tires with smaller circumferences to use in filling gaps where standard-sized tires don’t fit. Given the challenge of acquiring hundreds of tires of the same size, these gaps are inevitable.
• Be aware that some tires are softer than others, either due to lower quality rubber or being designed for different purposes. These softer tires are particularly useful, as they can be easily compressed to fit into smaller spaces or stretched to bridge larger gaps.
• Our tamper was 15kg, which is quite a lot — my heart rate was at 175 after a few tires. The benefit of this weight was that it did most of the work on its own, but we still had to lift it ourselves. Perhaps using a 10kg or even a lighter one would still compress the soil enough, albeit at more repetitions. But hey, my shoulders are now thiiiiiiiiiiiiiis wide.

Here’s how it went:

Oh, and what to do with any leftover tires? Plenty of things: