This article first appeared in The Owner Builder 196 August/September 2016. www.theownerbuilder.com.au
By Hannah Moloney
As we live on a steep slope we’ve had to build a lot of retaining walls in order to create functionality around access, water management and food production. We’ve used a range of techniques to do this including working with old car tires to build a big earthship-style retaining wall near our house.
Earthship construction is a building technique developed by American architect Mike Reynolds. He’s famous for using ‘rubbish’ and earth as building materials. We love his work. We chose to build an earthship-style wall as we had a small budget and a lot of excess subsoil left over from our initial earth works. We also knew we could get car tires for free from the local car yard who have to pay to get rid of them.
Check your soil
We hadn’t built one of these before, so we spent some time on YouTube learning how – there are plenty videos to watch. While it’s pretty easy, it’s also a lot of hard work. It would have been whole lot easier if we had heaps of people to help, one of those cool Wacker Packer tools and dry, gravelly soil instead of the wet and sticky clay subsoil we’ve got at our place.
This last tip is really important: the YouTube video we watched made it look like a walk in the park with dry, sandy soil in New Mexico. The builder just poured it into the tire and patted it down; in contrast we shoveled, packed, wacked and shoveled some more. It was a bit of a mission. But it’s an incredibly strong wall and used up much of our excess subsoil, for which we were grateful.
Plug, pat and pound
Starting out, we cleared the space, tacked some white geofabric to the bank to keep it from dropping crumbs and made a level pad to start laying tires. As we were almost on bedrock, we didn’t have to lay any sand or concrete for footings; we just leveled it off.
As soon as you start building up from your first tire, you have to find a way to plug the holes so the earth doesn’t just fall through. We had a pile of carpet tiles the previous owner had left under our house, which fitted perfectly, so we used them. We backfilled the area directly behind the tires with 20mm blue metal and agricultural pipe to guide excess water out of this area. In addition, drainage holes are also necessary, as you never want any water building up behind a retaining wall.
We went five tires high and angled them all slightly towards the back for structural integrity. An important thing to note is that if you go over one meter high for a retaining wall you need an engineer (in our region at least) to design and approve things, which can get complicated and expensive. Because of this, we didn’t exceed this limit – it might look taller below, but that’s because the earth around the wall had been excavated and the paving hadn’t been put down yet.
Plug the gaps
The next step involved plugging the holes between tires with subsoil. The best approach was to simply form balls of sticky soil, ‘peg it’ (throw it really hard) into the gaps and then pat it in to make sure it’s all bedded down. After that, we wrapped the whole wall in chicken wire. This is what the external renders ‘hang on’ and it helps create a smooth, level surface.
We chose concrete render instead of earth for two reasons: firstly, this wall is in the coldest, dampest area of the whole property so it needs to be able to handle long months of never seeing the sun and being constantly wet. Secondly, we’re not overly experienced with earth building, so we took the conservative approach.
The finishing touches
Recently we (as in, Anton) did the paving around this area using recycled bricks that were pulled up from our local town square. This was the final job to do before we painted the wall bright blue with a colorful patterned border.
Another nifty feature of our new wall is little steps leading up to our food gardens. The only downside to these steps is that our little daughter Frida Maria loves climbing them. When you’re not looking she’ll be up there in two seconds! We’re happy she has a great time there, but it’s just that the potential of falling onto the hard bricks below is a little too stressful for us. A little gate may be in order.
We’d love to see more people using recycled materials to build inside and outside their homes. The amount of ‘rubbish’ in our world is mind-boggling and when we look closer at so-called rubbish, you’ll notice that most of it could actually be re-purposed into a valuable resource. The possibilities are endless – we just have to pull our socks up and get creative!
*Just a quick note: car tires can have some leaching of chemicals, which we wouldn’t personally be comfortable putting near food gardens. So this wall isn’t near our growing beds. Everything downhill from it (the leaching will move with gravity) is all brick paving and house.
Hannah Moloney is the co-founder of Good Life Permaculture offering design and teaching centered around the concept of radical homemaking, placing home and community at the core in order to create a good life. www.goodlifepermaculture.com.au