Footings and foundations for warehouses in South East Queensland
By Brenscot Builders | Last reviewed September 2026
Above the slab, warehouses look alike. Below it, they differ enormously. Ground conditions across South East Queensland range from shallow rock to many metres of soft clay, often within the same suburb, and the ground decides what holds the building up and what that costs.
This article explains how warehouse foundations are chosen, the systems you will hear about, and why the ground investigation comes before the budget.
The short answer
A geotechnical engineer investigates the site and a structural engineer designs the footings and slab to suit the ground and the building loads. On good ground, a warehouse sits on shallow pad and strip footings. On soft, filled or variable ground it may need piles or ground improvement. The foundation system cannot be chosen, or priced reliably, without a geotechnical investigation.
Start with a geotechnical investigation
A geotechnical investigation for a warehouse, carried out in line with AS 1726 (Geotechnical site investigations), typically involves boreholes or test pits and laboratory testing, and reports on:
- The soil and rock profile, and the depth to a suitable bearing layer
- Bearing capacity and expected settlement
- How reactive the clay is to moisture change
- Groundwater level
- The presence, depth and quality of any existing fill
- Subgrade strength for slab and pavement design
- Acid sulfate soils, and how aggressive the soil is to buried concrete and steel, where relevant. A pre-purchase investigation is worth doing before you are committed. See industrial land due diligence
- Earthworks and foundation recommendations
The structural engineer then designs the footings for the building's loads using the AS/NZS 1170 series for loads, AS 3600 for concrete, AS 4100 for steel and AS 2159 for piles.
A note on AS 2870, which people often mention: it is the residential slabs and footings standard. Its scope extends only to buildings similar to houses in size, loading and flexibility. A warehouse is engineered from first principles, not designed from the house-slab tables.
Ground conditions to watch for in SEQ
Existing fill. Many industrial lots have been filled, some decades ago with little record. Unless there is documentation that fill was placed and tested as controlled fill, engineers treat it as uncontrolled and will not rely on it to support the building.
Soft clays. Low-lying land along the Brisbane River and other floodplain and estuarine areas can have deep, soft, compressible sediments. The Gateway Upgrade Project environmental impact statement reported up to 33 m of recent estuarine and alluvial sediments associated with the Brisbane River at the Gateway crossing. Sediments of this kind are often soft and compressible. Buildings on such ground settle unless they are piled or the ground is improved first.
Reactive clay. Clay that swells when wet and shrinks when dry moves slabs and footings. It is common across Queensland.
Shallow rock. Rock is an excellent foundation but slow and costly to excavate for footings, services trenches and stormwater tanks.
Acid sulfate soils. These occur in low-lying coastal areas. Under Queensland's State Planning Policy they are generally a consideration for land at or below 5 m AHD (Australian Height Datum, roughly metres above sea level), and for land below 20 m AHD where works go below 5 m AHD. Council planning scheme overlays map the affected areas. If disturbed, these soils generally have to be treated and managed under an acid sulfate soil management plan, and they can attack concrete and steel in the ground.
High groundwater. It complicates excavation for footings, piles, pits and tanks.
Controlled fill: the term that matters
If the building platform is built up with fill, how that fill is placed determines whether footings can bear on it. AS 3798 (Guidelines on earthworks for commercial and residential developments) describes two levels of oversight:
- Level 1: a geotechnical inspection and testing authority is on site full time during filling, tests the compaction throughout, and reports on whether the fill complies with the specification.
- Level 2: testing is done on a sampling basis only, without full-time supervision. The report covers the test results, not the fill as a whole.
Engineers generally need Level 1 documentation before they will design footings to bear on fill. Without it, footings usually have to go through the fill to natural ground, or the fill has to be excavated and re-compacted. If you are buying land, ask for the Level 1 report.
The foundation systems you will hear about
Pad footings. Isolated concrete pads under each column. The standard solution for a portal-frame warehouse on good ground.
Strip footings. Continuous concrete footings under walls, such as under tilt panels or blockwork.
Bored piers (bored piles). A hole is drilled to a deeper bearing layer, a reinforcing cage is placed and the hole is filled with concrete. Used where good ground is within reach beneath weaker material. They can be drilled into rock for high capacity. Groundwater and collapsing soils can require casing, which adds cost.
CFA piles (continuous flight auger). A hollow-stem auger drills to depth, and concrete is pumped through the stem as the auger is withdrawn, so the hole is never left open. The cage is pushed into the wet concrete. Low vibration, and suited to soft or wet ground where an open bored hole would collapse.
Driven piles. Precast concrete or steel piles hammered to a set depth or resistance. They produce no spoil, which helps on contaminated sites, but they create noise and vibration.
Screw piles. Steel shafts with helical plates, screwed into the ground with installation torque monitored as an indication of capacity. Fast, with no spoil and little vibration. Their capacity and corrosion life must match the loads and the soil, and they are not suited to every heavy building. They are designed under AS 2159 like any other pile.
Ground improvement. Instead of carrying the building through soft ground, the ground itself is improved. Options include preloading the site with a temporary mound of fill, often with wick drains to speed up consolidation, and rigid inclusions (unreinforced grout or concrete columns beneath a layer of compacted gravel that spreads the load) that support the slab and footings. Dynamic compaction can suit loose granular fill but not soft clay. Ground improvement can be the most economical approach for a large slab on soft ground because it supports the floor as well as the structure.
| System | Typical situation | Watch for |
|---|---|---|
| Pad and strip footings | Competent natural ground or Level 1 controlled fill at shallow depth | Soft spots, uncontrolled fill, reactive clay |
| Bored piers | Good bearing layer at moderate depth, or rock | Groundwater, collapsing holes, spoil disposal |
| CFA piles | Soft or wet ground, larger projects | Rig access and mobilisation cost |
| Driven piles | Deep soft ground, contaminated sites | Noise and vibration near neighbours |
| Screw piles | Lighter loads, fast programmes, limited access | Capacity, corrosion, connection detailing |
| Ground improvement | Large floor areas on soft ground | Time needed for preloading; specialist design |
Don't forget the slab
The floor slab is a structural element in its own right and is often the most heavily used part of the building. The Australian Standards in this area address other cases: AS 2870 covers residential slabs and footings, and AS 3727.1 covers residential pavements. Industrial floors on ground are designed to AS 3600 for the concrete itself, together with industry guides, mainly the Cement Concrete and Aggregates Australia guide T48 (Guide to Industrial Floors and Pavements) and the UK Concrete Society's TR34.
The design depends on what the floor will carry:
- Racking post loads, which are concentrated and often govern
- Forklift and other wheel loads, and the type of tyre
- Distributed storage loads
- Joint layout, which affects durability under forklift traffic
- Flatness requirements, which become strict for high-reach and narrow-aisle equipment
- Concrete strength. T48 sets minimum strengths for abrasion resistance, including 40 MPa for floors trafficked by non-pneumatic (solid) tyres
Tell the engineer what racking and equipment you plan to use, including what a future tenant might use. A slab designed for light use is very difficult to upgrade.
On soft ground, a building on piles with a slab on the ground will behave differently: the structure stays put while the slab settles. The engineer needs to address this, either by supporting the slab on piles or by improving the ground.
Frequently asked questions
Do I need a geotechnical report to build a warehouse?
Yes, in practice. The structural engineer needs it to design the footings and slab, and the building certifier relies on the engineer's design certificate. It should be one of the first things commissioned.
What footings does a warehouse need?
On good ground, concrete pad footings under columns and strip footings under walls. On soft, filled or variable ground, piles or ground improvement may be needed. The geotechnical report and structural engineer decide.
What is the difference between a bored pier and a screw pile?
A bored pier is a drilled hole filled with reinforced concrete. A screw pile is a steel shaft with helical plates wound into the ground. Bored piers generally carry heavier loads. Screw piles are faster and produce no spoil.
How thick is a warehouse slab?
It depends on the loads and the ground, so there is no standard answer. The engineer designs the thickness, reinforcement, concrete strength and joints for your racking and equipment.
What is controlled fill?
Fill placed in layers, compacted and tested under a specification, with geotechnical supervision and a report confirming compliance. Under AS 3798, Level 1 supervision is what engineers generally require before relying on fill to support a building.
Sources
- AS 1726 Geotechnical site investigations; AS 2159 Piling: design and installation; AS 2870 Residential slabs and footings (scope); AS 3600 Concrete structures; AS 3798 Guidelines on earthworks for commercial and residential developments
- Cement Concrete and Aggregates Australia, T48 Guide to Industrial Floors and Pavements
- Concrete Society (UK), Technical Report 34, Concrete industrial ground floors, 4th edition
- Queensland Government, Gateway Upgrade Project Environmental Impact Statement, groundwater chapter
- Queensland Government, State Planning Policy mapping for acid sulfate soils and the Queensland Acid Sulfate Soil Technical Manual
General information only
This article is general information, current as at September 2026. It is not a design or specification. Foundation and slab design for your building must be carried out by your geotechnical and structural engineers.
Planning an industrial warehouse?
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