Sloping land is ordinary ground on the Sunshine Coast — the hinterland ridges around Ninderry, Mons and Tanawha, the hillsides behind Noosa Heads, and plenty of coastal blocks that look flat from the road until the survey comes back. Measure the fall across your building envelope rather than the whole block, get a contour survey and a geotechnical report before you commit to a floor plan, and expect the cost premium to sit in retaining, drainage, driveway and access rather than in the house itself. Sunshine Coast Council and Noosa Shire Council both regulate what you may do to a slope, and they word it differently.
How do you assess the fall across a sloping site?
Slope is a percentage: 1.5 metres of fall over a 10 metre run is 15%. Get a licensed surveyor to produce a contour and detail survey, then read the fall across the building envelope you intend to use, not the block’s steepest corner.
Under the Sunshine Coast Planning Scheme 2014, steep land is slopes of 15% or greater, mapped on the Landslide Hazard and Steep Land Overlay maps in Schedule 2. Section 8.2.10 accepts a site-specific slope analysis prepared by a competent person as evidence your development area is in fact on land with less than 15% slope, even where the block is mapped. Then comes soil: a geotechnical investigation classifies the site under AS 2870 (Residential slabs and footings) and tells your engineer what the footings must do.
Cut and fill, split level, or a suspended floor on poles?
| Approach | How it works | Main cost driver |
|---|---|---|
| Cut and fill | Bench a level pad, balancing cut against fill | Retaining at the cut face and fill toe; spoil cartage; compaction testing |
| Split level | The house steps down the slope across two or more levels | Footings, stairs, drainage between levels |
| Suspended slab | A structural floor spans piers or blade walls; ground left largely as found | Engineering, formwork, undercroft treatment |
| Pole or stump | Piers founded below the slip plane, lightweight floor over | Access for piling rigs; services under the floor |
Council’s preference is written into the code. Where a dwelling house sits on land with a slope exceeding 15% as identified on a Landslide Hazard and Steep Land Overlay Map, the first acceptable outcome in section 8.2.10 is a split level design that steps down the slope, or suspended floor construction that avoids filling and excavation. The alternatives are tighter: confine any filling or excavation to the driveway and the plan area of the dwelling, with ground level retained around the driveway and the external walls; or cap it at 2 metres relative to ground level — 1.0 metre where within 1.5 metres of any property boundary — without necessitating a retaining wall exceeding 2 metres in height. Undercroft height at the perimeter of the building is capped at 3 metres above ground level unless you skirt, screen or landscape the full height.
Our Grandview Drive Extension at Coolum Beach is a pole home extended in every direction; it won three Master Builders Queensland 2025 Sunshine Coast Housing & Construction Awards. Elouera Drive at Ninderry is another hinterland project in country like this.
When does a retaining wall need engineering and council approval in Queensland?
Sunshine Coast Council states that building approval is needed for retaining walls over 1 metre in height, or within 1.5 metres of a building or other retaining wall, and that you must have council approval, as a concurrence agency, for retaining walls over 2 metres high. Approval is also triggered by repairing or replacing more than 20% of the structural components of a wall, adding additional load to the top of it — a concrete slab, additional fill, a raised garden bed, a pool — adding a fence on top, or increasing the height of an existing wall.
Surcharge is what catches people out: a driveway, pool or house footing near the top of a wall changes the design entirely. Council advises retaining walls should be constructed entirely on one allotment to avoid disputes, and that they are not normally a joint responsibility for neighbours the way a dividing fence is — though where a wall is constructed over and benefits multiple properties, the owners are jointly responsible. The QBCC requires a licence to carry out building work valued over $3,300, and the QBCC states that most residential building work in Queensland valued at more than $3,300 (including materials, labour and GST) must have insurance through the Queensland Home Warranty Scheme.
How do you handle drainage and stormwater on a slope?
Water is what damages sloping sites. Three jobs matter: a cut-off drain above the cut; subsoil lines and free-draining backfill behind every retaining wall, so the wall never holds water as well as soil; and roof and surface water taken to a lawful point of discharge without being concentrated onto the property below.
Sunshine Coast Council states that connecting to its stormwater network is subject to council approval, is to be undertaken by a qualified plumber and is at the cost of the property owner, and that council may become involved if water is being concentrated and directed onto a neighbouring property, or where roof water from new building work has not been connected to a lawful point of discharge. Building over or near council stormwater infrastructure is assessed against Queensland Development Code MP 1.4. In Noosa Shire, filling other than for driveways must not extend more than 1.5 metres from the outer walls of the dwelling house within the urban boundary (3 metres in rural areas), is limited to a maximum of 500m², and must not impact on the local drainage of adjoining properties.
How steep can a driveway be on the Sunshine Coast and in Noosa?
Under the Sunshine Coast overlay code, driveways are not steeper than 20% for more than 20 metres or one quarter of their length, whichever is the lesser, and not more than 25% in any location. Parts of a driveway steeper than 20% are provided with a slip-resistant surface, and vehicle turning areas are provided at the end of driveways so that it is not necessary to reverse up or down them.
Noosa Shire Council advises driveways within a property must have a maximum gradient of 20%, or a maximum gradient of 25% provided the section steeper than 20% is no longer than 6 metres and there is a transition zone at each end of the 25% section at least 2 metres long and no steeper than 12.5%. Noosa also requires a minimum grade of 1% sloping away from any adjoining buildings, and permits only one driveway and crossover per lot.
What is a landslide hazard overlay and does it apply to my block?
Both councils map it, under different names. Sunshine Coast Council combines landslide hazard and steep land in the overlay above. Where development sits in a mapped landslide hazard area, section 8.2.10 looks for a competent person to certify that the stability of the site will be maintained during the development and for its life, that the development will not increase the risk of landslide activity on other land including land above the site, and that the site is not itself subject to landslide risk originating from other land — with any measures identified in the site-specific geotechnical assessment fully implemented.
Noosa Shire Council maps a separate Landslide Hazard Overlay under The Noosa Plan 2020 and advises dwelling houses — including outbuildings and associated access — should generally not be built on land identified as a Landslide Hazard Area. Where there is no feasible alternative, Council requires a site-specific geotechnical assessment demonstrating the development can be safely designed and constructed to address the landslide risk and confirming it will not compromise the safety of people or property, with any risk mitigation measures recommended in the report implemented as part of the development. Check the mapping before you buy.
What do site access and crane costs add to a hillside build?
On a tight hillside block the machine that can do the job often cannot reach where the job is. Concrete goes in by line or boom pump; frames, trusses, steel and pool shells come in by crane; deliveries break into smaller loads; and retaining must be finished before the main structure starts. On our Grandview Drive Extension at Coolum Beach the figure-eight pool sits on stilts.
What actually drives the cost premium on a sloping block?
We will not quote a percentage, because it swings enormously with the site. It comes from, in rough order of impact:
- Retaining — length, height, surcharge, and whether it must be engineered and certified
- Earthworks — rock, spoil cartage, imported and compacted fill
- Structure — piers, blade walls, suspended slabs and steel instead of a slab on ground
- Stormwater and subsoil drainage, and reaching a lawful point of discharge
- The driveway, which on a steep block is a civil job, not a concrete pour
- Access — pumping, craning, smaller deliveries, slower trades
- Consultants — surveyor, geotechnical and structural engineers
- Approval pathway — a mapped overlay can turn a certifier-only job into a development application
Do I need a geotechnical report for a sloping block in Queensland?
Nearly always in practice. Your engineer needs an AS 2870 site classification to design footings, and inside a mapped landslide hazard area the Sunshine Coast overlay code looks for certification by a competent person, while Noosa Shire Council requires a site-specific geotechnical assessment.
Is a pole home cheaper than cut and fill?
It depends where the slope sits. Earthworks and retaining costs rise steeply with fall while structural costs rise more gradually, so every site has a point past which building above the ground beats reshaping it. Finding it needs a survey, a geotechnical report and a preliminary structural opinion.
Can I build on a block steeper than 25%?
A house, generally yes, with engineering. Subdivision is another matter: the Sunshine Coast overlay code’s acceptable outcome is that no additional lot which includes a house site is created on land with a slope of 25% or greater.
Roebuck Concepts is a licensed Queensland builder (QBCC licence 15280811) and a member of Master Builders Queensland, based at Coolum Beach and building across the Sunshine Coast and Noosa Shire. Send us the address and a contour survey and we will walk you through what the slope means for the build — see our consultation request, our new home builds on the Sunshine Coast, or the Elouera Drive, Ninderry and Grandview Drive Extension projects.