Hillside houses provide owners with beautiful views – but they can also present various problems with regards to outdoor living and gardening. If you're a fan of outdoor entertaining (or even just relaxing outdoors), a steeply sloping yard can limit your usable areas.
For gardeners, problems with sloping sites include things like soil and nutrient loss, as well as overexposure of plants to wind and sun, which can easily damage or kill them. Both entertainers and gardeners, however, can overcome these problems with a bit of planning, landscaping, and dedication.
Properly plan your drainage
Regardless of what you've got in mind for the garden on your sloping block, drainage needs to be considered every step of the way. It’s a careful balancing act – you want to prevent water from building up anywhere on site, but at the same time you don’t want it draining off all in a swift flood.
There are many, many ways to ensure even, consistent drainage, including installing drainage channels and sinkholes, smart planting, and contouring the land. Planning drainage right isn't always easy, and can affect things like stability and erosion. There's often a bit more to it than just digging a few channels. Planning drainage for a garden with a significant slope is often best left to a professional landscaper or engineer.
Create some terraces
Terraces are the most common way to to manage a sloping block – and with good reason. To create a terrace, there are two options: infilling or excavating.
Infilling is when a retaining wall is created at a lower point on the slope, which is then filled in with material to raise a flat area of ground. The main costs to this process are the creation of the retaining wall, and the cost of the material for the infill.
The obvious beneft to this option is that the newly created space is usually open to views on many sides. Depending on the size of your terrace, you may need to consult with your local council regarding by-laws about things like the height of the retaining wall, alteration of the landscape, and how the required drainage is arranged.
For all walls over 600mm, you'll need to consult an engineer to ensure the structure of the wall is strong enough to withstand the weight of the soil and water behind it.
Terraces can also be created by digging into the hill and establishing a retaining wall to hold back the remaining hill. The main cost involved with this process is excavating the material and disposing of it. The benefit to this approach is that a relatively sheltered area is created - which can be a big plus on a windy hill site.
One drawback to this option is that the exposed ground is often subsoil or substratum. Both of these substances lack organic matter or humus, reducing their ability to drain and support plant life. This can be overcome with careful reuse of the existing (excavated) topsoil, or by importing new topsoil - but you'll need to consider this beforehand and possibly budget for it.
As with infilling, an engineer needs to be consulted for any walls over 600mm and you’ll need to research the applicable local bylaws.
The best of both
In many cases, the most savvy landscapers will use both infilling and excavating – either on the same site or two different ones – to provide both material for the infill and a disposal for the excavation. If you’re planning a massive landscaping project, you should consult an engineer who can advise you on what’s needed.
Decks are another excellent way to maintain your views while creating a flat space for enjoyment on a heavily sloping block. To learn more about how to plan and construct a deck, check out our decking design guide.
Creating new flat areas on your sloping block is a good idea – but you’ll also need to be able to access them. If you’re already talking to an engineer or builder about your terraces or deck, you need to include access in the conversation. It may seem obvious, but stair design involves so many variables – such as descent gradient, step depth and height, and drainage – it’ll make your head spin! For the safety of your family and visitors, talk to a professional about step design.
In some situations (particularly for decks or areas where there's a significant drop) you may also need to consider handrails or other barriers.
Research and planning
As you can see, there’s a lot to consider when developing a garden on a sloping or hilly block. It’s well worth the trouble - hill gardens are often amongst the most beautiful in the world.