In My Own Backyard – Sleeper Retaining Walls
When we bought the house we were aware that some of the retaining walls were around 20 years ago and had either completely fallen over or were in need of repair.
We were faced with the choice of doing it all again in limestone blocks or rebuilding the sleeper walls. In a perfect world with endless $$ we would have chosen limestone, simply because of its permanence. But limestone was going to cost around $20K installed and sleepers around $1500 (if I did the work). To DIY with limestone it was going to be around $4K but I wasn’t sure I’d be able to do it alone with the size blocks required. The rest of the house is also timber and we liked the look of the sleeper walls so we thought we’d give it a shot and assume we would get at least 10 years out of the sleepers if not 20-30.
So began the process of building..
I had never built a retaining wall before so it was a new learning curve and as usual google made it easier. I researched the how tos of sleeper walls and then set a line and started digging holes. It is’t rocket science – just a bit of hard work.
The key with the holes is to make sure the post is at least the same depth in the ground as the height of the wall. My wall was going to be 900ml at its highest point so I made sure my holes were 1m deep. I used a long handle spade to get the sand out and while it was a little tricky towards the bottom I managed to get all the holes quite deep by scraping the sand and then levering it up.
Digging was the easy bit. Then came moving the sleepers…
They are 50kgs so not that heavy, but when you need to get them in a specific place and you are working alone it is a little tricky. I slid them onto the top of my wheelbarrow and moved them as far as I could by that means before lifting them into place. Once in place I used one bag of rapid-set around the base and then once set packed the holes with bricks to add strength. I only used one bag of concrete in case the posts need to be removed in the future. It was hard to get some of the original posts out minus concrete so I figured using 4 bags / hole might mean they never move, but it would also require some serious machinery to get them out once they rot.
Some of my reading suggested leaning the posts in towards the wall 2-5 degrees and allowing the wall to adjust the posts as it settled. However I had seen a neighbour’s wall where this methodology had been applied and his hadn’t settled (after 20 years) so I figured I would gamble on a perfectly pependicular wall and resolve the lean problem at a later date if it happened.
I placed the posts in, did the checks with the spirit level and allowed the posts to set in place. I used a piece of 2.1m pipe as a guide to mark the centres of the posts as a set of sleepers would be resting on either side of the posts. I actually managed to drop one post in the wrong place and pour in the concrete before realising and then needed to get it out of the hole. Not recommended… It was a real struggle getting that sleeper back out.
However once the posts are set in place the rest is just grunt work and some levelling. I dropped the first horizontal into place, got it level and then dropped another 3 on top. The wall stepped down towards the rear of the property so I made those adjustments as I went.
Once all the horizontals were in place I began to fill the area behind the wall with the bricks and rubble that had been left lying around the yard. I figured it would help drainage and also clean the place up – double win.
The finished product looks really good. Its got a great rustic feel and it ties in with the rest of the house. Even better it took me a whole 2 days of time working alone from go to whoa. I think limestone would have taken a lot longer.
We bought the sleepers from Mountain Movers in Burswood and got the 7ft ‘A Grade’ variety at $23.00/sleeper plus $80.00 delivery. As far as building materials go they aren’t cheap and it would have been almost as economical to build the wall out of concrete sleepers – except without the rustic look.
So we’re guessing they will be good for 20-30 years which is how long the originals lasted, but of course white ants could change that fairly quickly.
This weekend should see the completion of the retaining and then its on to getting the levels sorted, before reticulation goes in.