Legislation and horticulture? In your own back yard? What madness is this? Why are Australian Standards involved?
Planning permission is in many cases not a necessary evil, but a necessary safeguard, and retaining wall design standards exist because accidents happened years ago and with experience comes the determination not to let the same thing occur again. Standards Australia is the national organisation dedicated to keeping the country safe as regards things like construction, and Australian Standards is what we call the standards it sets out. In fact, Standards Australia oversees many different industries: anywhere public safety is at stake, they exist to ensure best practice is followed.
As regards retaining walls, it’s not just about determination: it’s knowhow. Techniques and equipment continue to grow in sophistication and power, making more things possible, but with bigger projects come bigger challenges.
When you are planning and laying out a garden, what are the rules? You may have done some drawings or even used a computer program to create a 21st century artist’s impression of what your spread is going to look like, at least before the planting begins and Mother Nature adds her own refinements and unexpected issues.
It is tempting to think there are no rules, because whose business is it if you put a bit of lawn here and a flower bed next to it, and maybe a patch of herbs right there near the kitchen door? What difference does it make to anyone, apart from the person doing the cooking, who can grab some fresh bay leaves any time they like?
This is true for most aspects of a garden, but there are situations where health and safety concerns emerge, and the building of a retaining wall is one of them. It stands to reason. After all, what is a retaining wall? It’s a wall that retains something. It holds something back. While most garden walls are little more than boundaries, denoting the edge of your property or the sections within it, a retaining wall is holding back a heavy mass, usually of soil but possibly sand or even water in the form of a raised pond or pool. When lifting and holding back are involved, a wall takes on an extra responsibility: the safety of anyone near it. And when safety is involved, governments get involved, particularly local authorities. Rules and regulations are drawn up.
In this case, the retaining wall design is in accordance with the Australian Standards, AS4678, the retaining wall design guide.
Some general points from AS4678 include the fact that the responsibility lies with the owner, even though they will probably not be carrying out the work.
Similarly, although a landscape gardener or concrete sleeper retaining wall specialist may undertake the work, they may also need to consult a structural engineer to advise on certain matters, especially if a wall is extra tall or the soil conditions are unusual/complicated. Soil types can vary, even within a small area, but a local contractor will have a better knowledge of the conditions you are working with.
Landscapers and professional gardeners are aware of retaining wall design standards, but for the private individual or landowner this may come as something of a surprise. It makes sense, though, and everyone has to abide by the law. The amateur can’t be expected to know instinctively about the potential problems and hazards associated with garden features, but ignorance is no defence, and this is as much a part of building regulations as anything concerned with the structure of the house. As regards retaining wall drainage, the Australian Standards have an official protocol that must be adhered to.
The lay person may have casually wondered what those holes are in walls that have earth behind them, and the answer is they are for drainage, because a build-up of water from even unexceptional quantities of rain can increase the weight of the soil and the pressure it exerts on the wall, and while walls are by their very nature fairly strong, they have their limits and drainage must be built into a retaining wall to prevent its possible collapse.
Holes in retaining walls may sound primitive but they can be extremely effective. If it occurs to you that you have never seen water trickling from them, perhaps that is because they have been quietly doing their job, so there has been no build-up of water behind them.
Other steps can be taken to assist with soil drainage, and of course prevention is better than cure, so the firm carrying out the work may spot a potential water problem further back up the chain of events and recommend that you deal with that. Diverting a stream or drain, for instance, can be a simple way of sending unwanted water in a different direction, preventing a potentially troublesome situation.
What is a wall made of, anyway? Most may be made of stone or brick, but for a timber retaining wall, Australian Standards has a category, and for general earth retaining structures Australian Standards has a broader one. Legislation deals in detail, so retaining walls have been studied so that there are no loopholes. The lawmakers take such pains in order to protect the population, not to catch us out.
Understanding Australian Standards for Concrete Sleeper Retaining Walls
With concrete railway sleepers fast becoming the automatic choice for building retaining walls, there is a nationwide need for understanding the Australian Standards for concrete sleeper retaining walls. Australian Standards are readily available and if you know the exact layout you propose to have for the retaining walls aspect of your garden, you can match the details with the regulations to make sure what you’re planning is acceptable. If it’s not, you will be able to revise your plans so they fall within the requirements.
Choosing a Professional for Your Concrete Sleeper Retaining Walls
Individuals wanting a retaining wall, particularly one involving concrete sleepers, will be engaging the services of a professional, because this sort of work is far too heavy, even for someone who likes to do their own work around the house and in the garden.
There are not too many options in this line of work for the simple reason that it involves machinery that the average gardening firm just doesn’t have – plus the fact that there are skills involved which, with the best will in the world, an all-round gardener doesn’t possess. It goes without saying, then, that the most enterprising and capable of private individuals cannot construct their own retaining wall with a few trips to the hardware store and a quick search on YouTube for a self-styled expert who will show in a couple of simplistic minutes how to do it.
An experienced professional will know about any local variations in legislation and can therefore avoid the sort of situation where you think you have followed the guidelines, but they were the wrong ones. Australia is home to many geological variations, and while the basic tools of the retaining wall trade – incredibly strong units such as concrete railway sleepers and, less often these days, wooden sleepers – are suitable for just about every application, each project has its own quirks and these need to be covered by materials and methods that are up to the job. A huge bank of earth, for instance, will need a bigger, stronger wall, and while it is always possible to arrange this, a thorough site check will be necessary to establish exactly what is needed.
