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Rock Science: building our gabion wall

May 6, 2011 | Appropriate Technology, Building, Natural Building | 41 comments | Author:

I am now fully convinced of the glory of gabions. Not only can they create leaky weirs in dryland gullies, they can also liberate courtyards. Like ours, for example. After years (yes, literally) of trying to figure how best to create a low-cost, low footprint, 2m high retaining wall in our courtyard, we discovered the solution. Wire baskets of rocks. Yes.

Previously, gabions always seemed to me the sort of thing you find next to a highway, holding up a mountain side. Or next to a government building. They seemed very official and well beyond the scope of a DIY home builder. I don’t know why I thought this. But it turns out they are our friends. Sturdy wire baskets ready to hold anything. Bring your own rocks.

Our courtyard-in-progress, looking mighty scruffy, unstable and lumpy. Note massive rocks.

The mission with this retaining wall was fundamental to building our tinyhouse at Milkwood. We had cut into the hillside to make a two-tier flat place: to build our small house, to harbor our kitchen garden, and to generally provide somewhere you could sit without tipping downhill.

The problem (ahem – i mean challenge) was that this cut then needed a retaining wall to stabilize the earth. Pretty simple, I hear you say. Well, kindof. The next challenge was that we soon discovered that our cut was full of immovable boulders. These massive lumps poked out of the ground and out of the walls of our cut.

After trying (and only partially succeeding) for 2 weeks straight to remove just one of these monster rocks, we decided to work around them. Our teeth gnashed and we swore we could hear the trolls cheering deep beneath the earth.

This wall, and our entire courtyard surrounding the tinyhouse, faces north-east. We wanted to create a space full of warmth in winter by using the retaining wall as a giant thermal mass collector that will then radiate that heat back into the courtyard in the late afternoon and evening on a winters day. So making this wall out of rocks seemed an obvious choice.

For the top retaining wall we started with a drystone wall, but we soon found it was not right for our build. The small 5m section we did with stonemason Maurice looked wonderful, but it took 3 weeks to collect enough of the right kind of rocks, and one week with two men to build it. There was no way we could keep that up for another 32m long by 2m high.

Our small drystone wall. Very lovely, but not the best solution for the whole courtyard (not on our budget, anyway)

So gabions became the solution . They were perfect for the job. We could alter the bottom and back faces of the the baskets to account for our boulders, we could use our own bush rock to face them with, and they were suitable to build with to 2 meters high.

If you’ve ever been to Ballast Park on Sydney harbor, you would have seen some serious gabion action. It turns out gabions can be quite a creative and pliable form, too. You can curve around corners, put anything you like in them, and get seriously funky if you chose. We, however, just wanted a wall. A good, old fashioned, heat radiating, lichen covered, rock wall.

The gabion baskets we sourced came in a range of sizes. We used one row of 1x1x2m baskets for the bottom course, followed by 2 courses of 0.5×0.5x2m baskets. When put together, they are literally a wire box with a lid. A bit like lego, but with added rocks. Our kind of fun.

We drove bits of iron bar into those immovable boulders so that the bottom course of baskets, when filled with rocks, would not be able to move or shift at all. Once the first course of baskets were filled we wired their lids on, and wired the second layer of baskets to the first, and so on.

Shane wires the baskets together. Note lumpy nature of earth cut.
Nick displaying the gabion baskets lego-like qualities, with hinged lids

We chose to collect rocks from our very rocky paddocks for just the facing (outer) layer of rocks in our gabion baskets, mostly because it would take a huge about of time to collect enough rocks to fill all the baskets. While i do love picking up rocks off our hillside, other aspects of life call after a while. So we cheated and got some ballast from our local quarry to fill the back of the baskets.

First course of gabion baskets half filled. Brown bushrock facing, with ballast (white) rock behind
East-facing gabion wall completed!

The result is a wall that, once it’s got espaliered orange trees growing up against it with prostrate rosemary cascading down from above, will look like it’s always been there. In the meantime, it looks like a big, solid solution to our big, tricky problem of how to prevent our hillside merging with our courtyard.

For what is a wall without resident lichen?

The gabion baskets we used came from Maccaferri Australia. They were very helpful to deal with, quick to deliver, and generally great. Thanks to Damien Stephenson (awesome Mudgee builder) for having the bright idea that we should be using gabions, and for telling us so.

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  • Michael Tanner

    Well done guys on a very neat job. I’ve used gabions extensively in landscaping (i think they’re a very good example of sustainable construction techniques) and for first timers you have excelled – no saggy joins or basket corners and the face rock placement is first rate – 10/10!

    • http://milkwood.net milkwoodkirsten

      Wow – a real live pro gabion builder thinks we did ok! Thanks Michael!

  • http://www.agoatinthegarden.blogspot.com Sharon

    Thats a great idea, might be something we can do for our house/retaining wall/courtyard area too!

  • http://www.sudeepbhaumick.com/ Sudeep B

    Hi,

    The benefits are quite compelling… the only question I have is how long do the baskets last?

    Have been following your journey since 2008 and have been greatly inspired by your example to take a similar plunge. Thanks.

  • http://zucchiniisland.blogspot.com/ Jason Dingley

    “next to a highway, holding up a mountain side. Or next to a government building” That’s is my impression of them too. For me it made it look like the government couldn’t afford the mortar. Interesting how seeing it in a different context changes ones impression. Is it cheaper and quicker than a mortar approach?

  • http://littlehousecollective.wordpress.com Joel Catchlove

    Nice work guys! I’ve often pondered why this technique doesn’t seem be much used beyond public landscaping projects, and you’ve convinced me of it’s value. Can’t wait to see it vegetated!

  • Gillian Newman

    Love that Mudgee red earth!

  • http://www.digginfood.com Willi

    Ooh! It is lovely. The rocks are so neatly stacked!

  • http://www.ptpc.com.au Harry

    Thanks Kirsten,

    I’m so impressed with all the projects that you guys have on the go and with which you do such a good job. Thanks for sharing it, too. I hope I get a chance to visit some day.

    • http://milkwood.net milkwoodkirsten

      Thanks, Harry! And good luck with your Mediterranean trip!

  • http://www.ptpc.com.au Harry

    Thanks, yes, I’m really looking forward to it. I get to hang out with Sepp Holzer in less than a month!!

  • http://www.thekebun.com Adrian Cornelius

    If you have any ‘spare’ yogurt you can use that to spray on the wall face but dilute with chlorine free water. Using yogurt will greatly encourage moss to grow which in turn make it cooler which in turn also encourage the little creatures to make a home in between the rocks.

    Great job by the way. Unfortunately we have to drive out to get rocks like those which are very large and weight quite a bit!

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  • Scott

    The wall looks awesome…Im about to do one at my place up in the northern rivers…How long did it take you to build…excluding collecting the rocks..Im having some delivered

    • http://milkwood.net milkwoodkirsten

      Scott if you’re just dumping the rocks in the wire cages, it’s very quick work, really. Doing the facing rock technique (our rocks on outside, ballast on inside) takes a bit longer… trying to remember – think it went at a rate of 6 or 7 baskets per day with one person?

  • Mefell

    Really nice job. We are looking at doing the same as we cannot get holes in rocky ground for posts to do any other kind of wall. Until we do the wall we can’t put up the shed.

    What tools did you need for the job?

    • http://milkwood.net milkwoodkirsten

      Thanks! Yeah we’re really happy with this wall… Tools were basically pliers and wire cutters to construct and close the baskets, and sledge hammer to sink the stabilising star pickets… It’s a simple build, just takes time… Have a rock party maybe?

  • http://twitter.com/NorthWoodsRanch North Woods Ranch (@NorthWoodsRanch)

    What is the anticipated lifespan of these baskets?

    • http://milkwood.net milkwoodkirsten

      From memory the warranty is 20 years, but if the wall has good drainage behind it they should last a lot longer (galvanised wire)…

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  • http://seemyfootprints.blogspot.com.au/ Kristy

    oooh this is what I thought of for walls for a house… maybe rendered or some other more solid finish but with big upright poles (put the baskets on first, pole through them and then fill with rocks) on a solid foundation… it was an idea anyway and I know I’d need to look into it more.

    thoughts?

  • http://aikidesigns.net Ben

    Rock fig or similar would probably hold it all together once the wire breaks down. How are you planning to vegetate it?

  • http://www.bananaorangeapple.com Hannah

    Hi there,
    I was wondering if the gabion walls make a habitat for snakes? We are thinking about a retaining wall near our place but we don’t want Joe Blake moving in quite so close.
    Any ideas?

    • http://milkwood.net milkwoodkirsten

      erm, well they could be I guess, especially if the rock sizes were bigger, which would mean more holes… but we haven’t had that problem?

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  • David T

    Would it have been possible to infill some of the top stone boxes with compost to grow & some nice frangrant vines to both scent and soften the gabion? Or, even grow something like loofah or squash that is a vine, that can draw moisture or any condensation from the sub soil behind the wall?? Just a thought :)

    I think it looks very cool as is too. Fits perfectly from an aesthetic point of view.

    I ask the above as I remember seeing a You Tube video with a guy who grew yellow squash, chokos, cucumbers, loofahs, even small pumpkins from pots hanging on the fence. He got the buckets from a florist for a buck a piece, hung them from his fence with chook wire nailed beneath them so the vines could trail. To me it’s begging for some “tasty” sections with vibrant green foliage, assuming the aspect is right of course. It could add to your home garden…?

    • http://milkwood.net milkwoodkirsten

      yep you could – that would work well :)

  • http://gravatar.com/foragerfam Andrew

    Just a question… has anyone used Gabion for foundations under mud brick, earthbag or load bearing straw houses?

  • http://andrewforager.wordpress.com foragerfam

    Has anyone used this system for foundations for Earthbag, Mud Brick, Rammed Earth or load-bearing Straw Bale houses?

    Also, there is another application for them: Gabion can be in-filled with sand-bags for noise reduction. I was talking to a company who do a lot of Gabion work in Adelaide this morning. The wall at the front of their shop-front on South Rd at Glandore is filled with sandbags that deaden the noise from this main road.

  • http://startingfromscratch2013.wordpress.com Mumof2Rs

    Hi Kirsten, I have just found this post after searching for gabion walls, as I have a current retaining wall which needs replacing, cut into a slope with very poor drainage and clay soils, and I am trying to be as green as possible. One concern I have about the gabion walls is the PVC coating on the wire. Can you see this as a problem if I want to plant vegetables around the top?
    Thanks
    Kali

    • http://milkwood.net milkwoodkirsten

      Hey Kali… erm, don’t think there’s pvc coating on our gabion baskets – it’s just raw galvanised steel?

  • Grey Nomad

    Where I live, SE NSW, dry stone walls are tiger snake havens.

    • http://milkwood.net milkwoodkirsten

      Yes I have been alerted to the fact that we’ve apparently built a snake magnet. Seems to be going ok so far though, 3 years in…

  • Miles

    Hi, am attempting a gabion wall of very similar dimensions to yours here in South Africa. Am struggling to stop them from bulging at the front and sides and as a result, to close the lids. Most of our fill is round sandstone rocks of various sizes. Is this due to poor packing? Any tips on how to keep the 4x1x1 baskets straight and neat.

    Regards

    Miles

  • http://milkwoodpermaculture.com.au milkwoodnick

    Hi Miles,

    Bulging is the biggest challenge when building gabion walls. Maccaferri have some very useful pdf downloads on this page that explain how to do it right. http://www.maccaferri.com.au/wawcs0137319/idDetails=166/Products-Gabions

    Basically it comes down to two things.

    Firstly, you need to wire all the baskets together and tension them together before adding any rocks. If you have built a high tensile wire fence before thats the kind of tension I’m talking about. Fencing end assemblies, a very big rock outcrop or a very solid wall will be needed at either end of the run and then you will need a winch or a wire strainer to pull the baskets tight (very tight) and a few fencing skills to tie off the wire.

    Once you start filling them (and we did this by hand to make it neat) you need to fill one third with rocks then tie the front of the basket to the back with wire that you tension with a spanish windlass, then another third then more spanish windlasses then the final third then close the lid.

    All this might sound a little tedious, but compared to a dry stone wall it goes very quick :)

    good luck

  • Bill

    Hi there, interesting and nice job. But I don’t really understand the why?

    I’m thinking of using gabions, for a 3m high bank, which I will form part of an outhouse structure (I don’t mind some water penetration). I’m thinking of how I can hide the gabions. I don’t find them attractive. Dry stone walls on the other hand I find exquisite. Did you plant over them?

    Have you got a picture of the gabions complete, an after shot?

    Thanks.

    • http://milkwood.net milkwoodkirsten

      The why is in the time (and explained in the article) – drystone took 4 weeks to do 1.5m, gabions took 2 weeks to do 8m…

    • Debs

      I love the look of gabion! am i on my own here?

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  • Brendan A. Creaner

    Has anyone used Gabions [infilled inside gabion-wall with earth] as a house foundation? I’m planning a 13x23m gabion-box, filled with compacted earth, on which I plan to put a 200mm concrete ‘lid’ [about 145 tonnes weight], as a base for a ‘normal’ breeze-block house of about 300 tonnes gross weight. Is that OK?

    • Kirsten

      I have seen it done, thought not sure whether that correlates to the specifics of your request Brendan, sorry!

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