Solutions For

Sloping Sites


Using Spantec products to build on sloping sites

For many homeowners, building on a sloping site is often unavoidable when building your dream home. You want to be elevated and you want a view, so building on a sloping piece of land often comes with the territory. Other benefits of building on sloping land include more natural sunlight, better natural drainage and ventilation, the opportunity for more interesting home designs due to the extra space, and ultimately a property with higher value.

Building on a sloping site can be challenging and costly, but it can be made easier and cheaper by choosing the right type of building materials. But what constitutes a sloping site?

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Classification of a sloping site

Steep sites are classified as difficult sites. A sloping site is generally any block of land with a slope of more than 6 degree, generally speaking, the steeper the slope the more complex the design of the home will be and the more it will cost.

Matching building design to suit the degree of slope

  • a1 Flat to slightly sloping sitesSingle slab on ground construction is only suitable for a site slope up to seven per cent. Slopes between seven and 10 per cent, should accommodate some level change within the building footprint.
  • a2 Moderate slopeFor slopes between seven and 20 per cent, stepping two or more slabs or using part slab/part post or beam construction would be suitable to handle the slope. Single slab on ground construction is not recommended
  • a3 Steep slopeFor slopes between 20 and 33 per cent, post and beam construction should be used which steps with the site. This may include a lower part level with a concrete slab. Single slab on ground construction should not be used.
  • a4 Extreme slopeFor slopes more than 33 per cent, suspended or pole construction techniques are required. This degree of slope isalt=”sll” more suited to a downslope configuration. Driveway access is generally too difficult on steep upslope lots which require large batters/retaining walls and sometimes a curving driveway.
Minimising building costs on a sloping site

The key to minimising the cost of building on a sloping site is to work with the site as much as possible rather than against it.

Cutting and filling, the process of creating a flat site on sloping land (see below) is expensive and can create significant additional costs for retaining walls or spoil removal. One of the largest issues is that hills are generally made of rock, you can expect the ground of a sloping site to be a lot shallower than usual, it doesn’t take much digging to hit rock, with this in mind you want to try and minimise the amount of excavation that’s performed to keep costs down.

Fill process

Home owners or builders can often completely avoid these issue by using a large spanning bearer and joist system. This may include a steel raised floor system that follows the slope of the land in a single storey, split level or multi-level construction.

As an alternative to pouring a concrete slab on the ground, a raised floor system can enable even more ability to work with the natural slope on your block of land.


The benefits of a raised flooring system on a sloping site

The benefits of using a raised floor on a sloping site include:

  • Easy access to plumbing and electrical services
  • Extended living spaces
  • Better pest control
  • Room for storage/car space under the house
  • Improved Ventilation and air flow
  • Higher Elevation for better views
  • Better use of light
  • Overall ascetics
  • Make use of a cheaper block of land
  • Reduction in plumbing costs
  • Minimal excavation and impact to land
What to look for when researching a raised floor system for your sloping site

When choosing a raised floor system for your new home, consider the following critical factors:

  • Is the floor system certified?
  • Does the design of the raised floor take into account your specific site requirements?
  • Are adjustable piers provided in your floor kit?
  • Has the design and certification taken into account the footing sizes and bracing layouts?
  • Durability.
  • Termite and Rot resistance.
  • Ease of assembly and range of brackets.
  • Light weight – especially important when working at heights.
  • Reduced excavation costs – such as less piers and no cut and fill.
  • Non-combustible.
  • Easy to level with adjustable piers – especially at height.
  • Straight and true product.
  • Detailed construction drawings.
  • Accuracy of design and materials.
  • Is it engineered for point loads, footings, bracing etc?
  • Minimal deflection criteria, reduced bounce.
  • No or minimal need for retaining or supporting walls.
  • Years of experience in just doing floors.
  • Minimal disturbance to the environment due to increased pier grid.
Boxspan steel floor kits by Spantec

Spantec is a long-time supplier of innovative steel building products for home builders across Australia. Our Boxspan steel floor kits are uniquely designed to meet all the requirements of building on sloping sites while also offering durability and installation efficiencies. With a Boxspan steel floor kit from Spantec you will get:

  • All Spantec products are certified.
  • Spantec individually design each raised floor.
  • Ezipiers are provided with every raised floor kit.
  • Certification is provided for footings, point loads, bracing and state form requirements.
  • All Spantec products galvanised, providing increased durability.
  • Manufactured from steel, no termite issues, product is straight and true to size and will not warp or rot.
  • Light weight bearers and joist that are produced using a patented manufacturing process.
  • Box like shape provides simple bracket connections.
  • Versatile, easy to assemble flooring kit.
  • Long spans, less piers- reducing excavation costs
  • Spantec have 30 years’ experience in design and manufacturing floor systems.
  • Time saved on site waiting for brickies/other trades, our system is simply screwed together.
  • Boxspan bearers and joists manufacture precisely to length to avoid wastage.
  • Components that are manufactured to extremely tight tolerances, ensuring they are straight sand true to size.
  • Non combustible, perfect solution in bushfire prone areas.
  • Minimal bounce through our experience factor, strength in product and design.
  • Detailed construction drawings provided with every floor design.

Spantec Solutions

  • Boxspan ticks all the boxes
  • Proven solution for sloping blocks
  • Proven solution for bushfire zones & termite areas

Our Boxspan Steel Flooring System is a unique solution for efficiently and accurately meeting the challenges of building on sloping sites. We do this by providing:

  • A comprehensive kit with all bearers, joists, brackets and fixings. As well as our ezipier adjustable steel piers and ezibrace.
  • A design and engineering service providing a full set of working drawings, this includes all beam layouts, connection details and pier layouts.
  • Every bearer and joist that arrives onsite is cut to size, each beam is labelled with size, length and marking relation back to working drawings.
  • Bracket location holes are pre-punched and each bearer carrying clear identification as to how it is assembled. Saving time on site installation.
  • Non combustbale materials that are manufacture to ensure accuracy.
  • Year of development on connection details make for a simple floor assembly.

The Boxspan Steel Flooring System is a unique solution that takes the pain out of building on sloping sites. Just ask Joe Simundza of Southern Belle Constructions, who used the system to successfully build a family home on a site with a severely sloping fall of 22-degree and up to 30 degrees in places.

A self-confessed “old-school carpenter and builder”, Simundza had to think outside the box to deliver the project. He chose to use the Boxspan Steel Flooring System from Spantec, and never looked back, and his challenging build was simplified.

“This process saved us many days and a lot of back-breaking work [and was possible] because the beams are so much lighter than what I have used on other sites,” he says. “The Boxspan system saved us around four to five days per floor, or about 16 to 20 days for all the floors — and we saved about $20,000 on machinery.”


Andrew and Rachel Cummins were building their rural dream home in the Hawkesbury region northwest of Sydney with a floor and deck structure that would cover 690m2. Their chosen site had a slope which fell approximately 2.5 degress north across the width of the home, was in a bushfire and termite prone area, and was also found to contain Hawkesbury sandstone. All of these challenges required them to find an alternative to timber for their wall frames, roof trusses, sub floor and deck structure.

“As we wanted to use a tongue-and-groove floor over a plywood base, we required a sub-floor that had no bows or twists, was made of steel, and provided a solution that gave us peace of mind in the location in which we were about to build,” Andrew said.

“Spantec had a large selection of different sized beams, which worked well with my design, and offered us a design package that came with a full set of site drawings, which we found to be very accurate. I found the service to be excellent.”



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