Australia has a lot of sloping terrain as part of what makes our landscape so unique. Some of the country’s most breathtaking homes are built on hillsides that provide proud homeowners panoramic views of the magnificent city skyline, white-sand shores, or beautiful bushland.
If you’re now also planning to build your dream home on a slope, there are some great sloping block solutions that can turn that dream into a reality. Building on inclined land seems challenging, but there are ways to make it efficient and cost-effective.
The most important thing is to hire an experienced sloping block builder with the knowledge and skills to tackle the job. It is important to note that building on an uneven lot is not a one-size-fits-all task. Terrain across Australia has unique characteristics and challenges, but a reliable home builder knows the local area, as well as the best contractors and earthworks services to get your lot ready to build on.
Keep the whole block in mind when working with your designer in planning your home. Looking at the bigger picture highlights the block’s potential while providing pockets of useful space for you and your family. Look beyond the four walls of the house, including how indoor and outdoor spaces will be used once your home is ready to live in.
There’s a world of ideas for the savvy sloping block home builder. Read on to learn more about your options for building on a steep property.
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What Are the Best Solutions for Building on a Sloping Block?
Levelling a sloped block of land, building a split level home or building on stilts are the most common ways to build a house on sloping land. All three options have pros and cons, so the characteristics of your lot will determine which approach is best.
Building on stilts is often used to make the most of stunning mountain views or other picturesque scenery. On the other hand, levelling a site to build on – including the use of terraces or retaining walls – transforms your lot and provides a more typical surface to build on. Split level homes also allow you to approach the lot with typical building techniques, though home design is a critical stage in split level homes, ensuring your finished home is extremely liveable.
To learn more about these steep lot construction options, keep reading below.
Levelling A Building Site
A house on a sloping block can be designed as though it was on a level surface by applying a “cut and fill” process. This method is used to level out land by cutting away soil on the high side and transferring it to the low side of the block. The result is a flat plane where a concrete slab can be placed.
Another option is to bring in soil from another source to fill the plot and make it level. Soil can also be dug or “cut” from a slope and used later to support retaining walls, giving you a range of options from similar earthworks processes.
Wondering if you can level your sloping lot to make your home build easier? Here are the pros and cons of levelling or ‘cut and fill’.
Pros Of Levelling A Sloping Block
Simplifies the Construction Process – Once levelled, the block can be approach like any other standard lot, reducing the complexity of the design and build process.
It Provides More Shade – This build method can result in having more shade around the home due to the tall retaining walls.
Complies With Local Council Bylaws – Some local councils enforce uniformity in homes in their areas; they do not allow a structure to be significantly higher than the other. They highly encourage cutting and filling to maintain a single level floor area.
Cons Of Levelling A Sloping Block
More Resource-Intensive – Backhoes, rammers, and loaders are the heavy equipment needed to excavate, fill, and compact the earth. This method also involves more time, fuel, and manpower to accomplish. This adds complexity to the construction process compared to typical site works.
It’s More Expensive – Since more resources are needed, the ‘cut and fill’ apporach does come at a higher cost than regular earthworks and site preparation. Aside from the cost of excavation, engineering services are often required to ensure everything is safe and sound before construction starts.
Since the surrounding soil needs to be retained when you excavate two to three metres into the ground, you need to build specially engineered and water-resistant walls, which can put a dent in your budget.
It’s also important to note that the deeper you excavate, the higher the risk of striking rock. A detailed survey and soil testing will help you understand what may be lurking under the surface of your block.
Logistical Challenges of Cut and Fill – Levelling a lot often requires additional space to keep excavated soil prior to filling, or as a staging area for equipment during the earthworks process. You may need to secure a vacant lot near the site to use for this if the majority of the block will be involved in the cut and fill process.
Access Challenges for Equipment – Access to higher parts of the slope can be quite a challenge when using heavy machinery for excavation. Difficult lots may require cranes to move machinery and remove soil. Sometimes, it is impossible to use a machine, so workers have to do it by hand, which can be time-consuming as well.
Erosion Risk Needs to be Addressed – When you remove topsoil and vegetation, the slope becomes susceptible to soil erosion due to the changes in soil stability. Excavating the soil disturbs its natural composition, making it “aerated” or “fluffed.” To prevent erosion, the soil needs to be compacted. If not done properly, it can result in serious consequences such as cracked foundations or crumbling floorwork.
Split Level Homes
Perhaps the most popular design for sloping blocks is the split-level home. Designers recommend it for a sloping site with a fall of three or more metres. As opposed to the traditional home layouts of having two distinct storeys, split-level homes have shorter levels connected by a short flight of stairs.
Split level homes often have the following features:
- House follows the contours of the land
- Higher ceilings can often be incorporated
- Steps are required inside and outside the home
- Bridges, balconies, and large-scale windows help maximise views
- A garage can be built under the home
- Various living and entertaining areas can be built on different levels
Could a split level home be the best option for your steeply sloping lot? Here are the pros and cons you’ll need to consider.
Pros Of Split-Level Homes
It’s Less Expensive Than Other Methods – A retaining wall isn’t required because whether you’re entering through the front or back door, you’re entering at ground level. Also, during construction, there is no need for heavy equipment and a staging area. The cut-and-fill method will also be reduced. All of these will significantly decrease the cost.
An Architecturally Unique Design – Split-level homes are interesting to look at from the outside, but it’s more breathtaking from the inside thanks to natural lighting and opportunities for scenic views. The different pockets of spaces in varying levels are a delight to decorate.
In a split-level home, there can be space for everyone in the family. Mom and dad can have a home office tucked away under one of the stairs, while the older kids can entertain in the games room in the basement.
It Offers More Yard Space – Due to the staggered floors of a split-level home, there is more room for living spaces. Instead of expanding horizontally, rooms are added vertically without taking much yard space. The garage is usually located on the yard level while the bedroom is built on top of it.
It’s A Good Investment – Homes that are constructed on sloping sites can command a higher price on resale than the average property – if your builder can bring out the block’s best features. If you plan on selling in the future, a well-designed split-level home can provide you with a greater return on your investment.
Cons Of Split-Level Homes
The Exterior Steps May Be A Hindrance – Most split-level homes feature exterior steps that lead to the front door. Unlike homes built on a flat surface, a split-level property can have two to eight steps before the main entry door. While this may be a plus feature for those who want to sneak in a bit of a cardio workout, the extra steps may hinder the elderly.
It May Entail A Lot Of Indoor Climbing – If climbing up and down the stairs outside is already a daunting task, moving up and down inside is almost a guaranteed challenge. Family members must go up and down the stairs to use a different part of the house. Imagine traversing three levels repeatedly just to clean or haul dirty laundry to the washing machine that is located on the lowest level.
Renovating May Be Challenging – The layout of a split-level home isn’t conducive to many changes since each level is made for a specific purpose. Usually, the dining and living areas are on the main level, the recreation space on the lower level, and the sleeping area on the upper level. This design may have little leeway for when you want some changes.
Building On Stilts
Steep, sloping sites can be addressed by building on stilts or columns to minimise soil disturbance. Stilting also creates a much smaller footprint after the whole construction process.
The need for cut-and-fill can be significantly reduced by using piers and posts. The most difficult sites can be accommodated with the most innovative foundation structures.
Pros Of Building On Stilts
It Is Cost-Effective – Since there’s no need for expensive foundations or excavation, the cost of building on stilts is significantly cheaper than the “cut and fill” method.
It Offers Design Flexibility – This design can be applied on multiple levels and leaves more room for creativity.
It’s Less Invasive – Building on stilts minimises alterations to the substrate. There will be no problem with disturbing the surrounding ecosystem.
You Can Maximise The Views – If natural views surround your block, then building on stilts is a great option. The increased floor height gives you a much better look at the landscape around your property. Just imagine having windows and a deck where you can always catch a glimpse of the sunset or the captivating city lights.
Cons Of Building On Stilts
The Design May Be Limited By Regulations Or Restrictions – Some local councils may restrict building an elevated home on your property. Your design may be limited to a specific building height. Your design may be restricted by laws limiting the allowable building height near boundaries for smaller blocks.
There Is More Exposure To Outdoor Elements – Since the house’s underfloor is open, it can be more exposed to elements that can affect the effectiveness of the insulation.
Getting The Most Out Of Your Sloping Block
The main key to getting the most out of your sloping block is to achieve balance. There are financial considerations that go hand in hand with the home design and the layout of the sloping block. There must also be a perfect balance between adhering to building regulations and preserving the magnificent views.
The way the block slopes dictates an ideal design for your home. For example, if the slope rises from the road, the best solution would be to build the garage underneath the house. The living areas can also be open out at ground level and located at the back.
On the other hand, if the block goes down from the road, it would be best to build a split-level house that follows the contour of the downward slope. You can build a utility area or game room at the back. Having a place to spend time with your loved ones or to store your hobby equipment is a neat idea. Tuesday game night is so on!
You can take advantage of solar efficiency together on top of enjoying the views by considering the orientation of your property. Main living areas can face north, for example.
Take note that soil depth is relatively shallow in a sloping block. There is a good chance that you’ll strike rock. Your best bet would be to work with the block and not against it to avoid unnecessary excavation and additional expenses.
There is no straightforward approach to building on a sloping site. There may be challenges not usually present in a building on flat land, but an experienced sloping block builder will know exactly what method to use.
Sloping Block Contour Surveying
The first thing that needs to be done prior to the construction of a structure on a sloping block is contour surveying. Generally, the results of the survey show the slope of the land. The results determine the best design for your home, the method to use, and how to work around the natural formations surrounding your block.
Aside from showing the exact slope of the land, a contour survey also identifies the exact location of power, data, and telecom cables. It shows the neighbouring features that allow your builder to make the best design fit for the contour of the land.
Most importantly, a contour survey assesses environmental hazards such as soil erosion and landslide susceptibility. A builder engages the services of a land surveyor. They provide the needed drawings and data to allow the design team to identify the height of the retaining walls, if required and the correct driveway grade.
Keep the following tips in mind in interpreting a Contour Survey.
- Contour lines that are closely spaced means a steep slope.
- Contour lines that are widely spaced means a gentle slope.
- Contour lines that have equal spaces in between means a uniform slope.
The points on a single contour line always have the same elevation. As a rule of thumb, the greater the slope of the land, the higher the cost of building the structure. However, a good approach and layout help reduce the overall cost of construction.
Sloping Block Soil Testing
A geotechnical engineer performs soil testing to check if the soil is stable enough to withstand the stress and weight of construction. This process is usually done together with the contour survey. The soil testing and survey results will either green light or halt making your dream home a reality.
If the soil test reveals too much moisture content in the soil, it means the moisture buildup won’t hold the structure’s weight. The test can also show the existence of subsurface rocks, which would require excavation and additional costs.
Also, the presence of deep tree roots, high-water tables, and other substrates such as sand or clay are all issues that need to be considered before taking the leap.
Choosing A Builder Who Specialises In Sloping Blocks
The most vital consideration when designing your home on steep land is choosing an expert sloping block builder who can give you the most value for your hard-earned money.
There are many home builders with varying construction specialties. But if you choose one who does not specialise in sloping block projects, everything might go downhill.
Inexperienced slope builders often tend to remove the slope instead of working around it, defeating the purpose of buying the lot for the views and unique qualities. Removing the slope is more costly than creating a floor plan to suit the topography of the slope.
Building a house on a steep block is far more challenging than building on a flat piece of land. An expert on slope building knows what design and method work, and they’re used to building on difficult blocks.
Slope builders already have extensive experience in moving materials up the slope. They are prepared to work with the block instead of against it, so construction is more cost and time-efficient in the long run.
Sloping Block Home Designs: What To Consider
The results of the contour survey and soil tests, the local council’s regulations, and the views need to be considered in designing a sloping block home. The following factors are also crucial in determining how to go about building your home.
Direction Of Slope
The following are the different categories of sloping blocks. The type of slope helps in determining the best method and layout to use.
- Sloping down – the high point is located at the end of the road
- Sloping up – the low point can be found at the end of the road
- Cross fall – the slope is from left to right or vice-versa
- Cross fall plus sloping – a combination of the above categories
Blocks that are sloping up provide the best opportunity for your property to have captivating views of the surrounding area.
Expert builders recommend digging into the site to create an undercroft garage for a sloping-up block. The result is often a three-story structure appearing at the front and a two-storey one at the back. Another option is having a two-storey appearance at the front and a single-storey at the back flowing into the backyard.
Sloping-down blocks can offer a back view overlooking breathtaking geography such as a valley, an ocean, or a cityscape.
A block that slopes down has more challenges than a block that slopes upwards—for example, respecting the neighbour’s privacy and complying with regulations on overlooking structures.
It’s important to note that whatever the orientation of your slope, the most crucial factor to consider is the angle of the slope. The angle dictates the scope of the design and the entailed costs. A gradual slope often has fewer design challenges and costs than steep slopes.
Remember that there will be more challenges in building on a steeper block, but if your builder can pull it off, the rewards will be great.
A house built on a sloping block offers a daily dose of amazing views. Homes on sloping sites are positioned to capture the beauty of their surroundings that can’t be experienced on flat land. The stunning views give more value to the property, which makes your investment worth it.
However, the design of the home must not overshadow any neighbours’ house. Consider any possible obstructions to your neighbour’s views or their privacy.
One of the standout features of a house built on a sloping block is the amount of natural light that bathes the home. Bay windows maximise the natural light, which is not only healthy but can also cut energy costs.
Where the windows are positioned is important; it’s best to position the largest windows to the north or east to catch the morning light. Using passive solar design can increase the energy efficiency of your home as well.
A proper drainage system is crucial to building on a slope. Landslides are a serious matter, so attention to drainage on both surface and subsurface water is non-negotiable.
It’s vital that rainfall runoff needs to be redirected away from the foundation of your house. This should be done without flooding public roads or endangering your neighbour’s homes.
Also, to prevent water from pooling, retaining walls need to be waterproofed or “tanked” and drained. Usually, culverts and swales are used to channel the water to the drains.
If your home’s basement is located below a high water table, you can prevent the problem of subsurface water from leaking by installing French drains or a sump pump.
Exposure To The Elements
The climate and plant life in the area must be considered during site analysis. Wind direction, sunlight exposure, rain volume, seasonal conditions, and other environmental factors are important to consider in maximising your home’s best conditions and safety.
If the area is prone to heavy rainfall, there is a higher risk of flooding and erosion, so an efficient drainage system must be in place.
Generally, a structure on flat ground is protected by natural topography or other buildings that serve as windbreakers. On the other hand, a house built on a slope may not have these features, which can make your property more vulnerable.
The best solution is to choose the highest quality building materials and discuss your safety concerns with your builder. They know exactly how to work around environmental factors.
Outdoor Spaces And Landscaping
- Flat land is usually easier to navigate. However, a sloping lot is more interesting and unique to the landscape. It would be best to plant foliage that can thrive on a slope, such as Westringia, Grevillea, or Native Violet. To prevent erosion, make sure you follow the tips below
- Plant a lot, especially those with good root systems. The roots of the plants help hold the soil together
- Use native plants for longevity and ease of maintenance
- Buy tubestock plants for faster, more efficient planting.
- Provide a bit of depression around the plants for runoff water collection
Terracing also helps maintain the integrity of the slope by preventing erosion. An age-old technique used by many farmers worldwide, terracing involves cutting a slope into a series of flat surfaces or platforms, which resemble steps. The walls of each terrace are reinforced by retaining walls, which hold up the soil effectively.
Note that the terraces hold up a lot of pressure and groundwater, so the retaining walls must be sturdy, preferably with a drainage system. Some excellent materials for retaining walls include stone, brick, and concrete. Ensure your retaining wall is waterproofed or has built-in drainage to ensure water buildup won’t weaken or damage the structure. Use plants such as thyme, candytuft, and creeping phlox to make your retaining walls pleasing to the eye. Potted plants and decorated switchbacks can spruce up a sloped yard.
How Do You Fix A Sloped Backyard?
The best way to fix a sloped backyard is to use a landscaping technique called backyard levelling. This technique involves surveying the area that needs to be levelled and determining how much soil needs to be removed. The process of excavating excess substrate levels the ground.
A retaining wall and a lot of hard base subsoil are often required to keep the level ground from slumping and eroding back into a slope.
Can You Build A Garage On A Slope?
It’s definitely possible to build a garage on a slope. The foundation can be constructed to make up for the slope, and this may involve some excavation or cut and fill. As long as the foundation is built properly, there shouldn’t be any issues building a garage using typical methods. It’s always best to check with an expert who can handle this challenging project. Precise measurements are essential to getting a safe and sturdy result.
Greg has over 40 years of experience in the WA building industry starting as a carpenter joiner.
He is entrenched in the local industry and has served on the board for MBAWA (Master Builders Australia WA) for over 10 years and was a founding director of Wesbuilders Cooperative for over 11 years.
With this experience he is able to quote accurately on new projects without the huge increase to provisional sum allowances.