Screw piles win on speed, wet weather, tight access and reactive clay; bored piers socket into rock and carry very high point loads, but need drilling, a cage and a cure. For a typical South East Queensland residential site on reactive clay or coastal sand, screw piles are usually the fastest, cleanest and most certain option because every pile is torque-tested as it goes in and there is no cure delay. Where solid rock sits shallow, a bored pier can be the better answer. The soil report decides.
The two systems at a glance
Once a soil report moves a site off a standard footing, the real choice is between two deep foundation systems: screw piles or bored concrete piers. Both carry the load past the weak upper soil onto competent ground. The question is how you get it down there, and what that costs you in time, mess and certainty.
Screw piles are steel piles with helical plates wound into the ground like giant screws, founding the load on competent soil below the weak upper layer, with no excavation and no concrete to cure. Bored concrete piers are holes drilled deep, reinforced with a steel cage and filled with concrete, founding load at depth much like a pile but poured in place.
Side-by-side comparison
| Factor | Screw piles | Bored concrete piers |
|---|---|---|
| Installation time | Hours. Ready to build on immediately. | Days: drill, cage, pour, then cure before loading. |
| Site disturbance | Minimal. No excavation, no spoil removal. | Moderate. Drill spoil to manage, concrete access needed. |
| Wet weather | Can usually install in and after rain. | Holes can collapse or fill; often needs lining. |
| Reactive clay (most of SEQ) | Excellent: founds below the movement zone. | Good, when drilled below the active zone. |
| Sloping or tight-access sites | Excellent: installed by compact machines close to boundaries. | Possible, but rig access limits steep sites. |
| Load verification | Every pile proof-tested by torque as installed. | Relies on inspection; testing costs extra. |
| Shallow rock sites | Depends on depth and rock type; may need pre-drilling. | Good: piers socket into rock. |
| Very high single-point loads | May need pile groups or larger piles. | Excellent for heavy point loads. |
| Spoil and waste | Almost none. Nothing to cart off. | Drill arisings to remove and dispose. |
| Removable / reusable | Yes: can be unwound and reused. | No: demolition only. |
Screw piles
A screw pile is wound into the ground by a hydraulic drive head on an excavator, and the torque it takes to drive it correlates directly with the load it will carry, so every pile is effectively proof-tested as it goes in. On our machine that torque is read by a load cell against the engineer's number, and logged. There is no excavation, no spoil, and nothing to cure, so the structure can be built on straight away, the same day.
Where they win: reactive clay, deep sand, sloping and tight-access blocks, wet-weather programs, and any job where the certifier wants documented load records per pile. Where they do not: solid rock at shallow depth, ground full of obstructions, and very deep soft profiles with no competent layer within economic reach. We publish the full list in when screw piles are the wrong choice.
Bored concrete piers, and bored piers vs screw piles
A bored pier is a hole drilled to depth, reinforced with a steel cage and filled with concrete, founding load deep like a pile but cast in place. They are the heavy-load specialist, and they can socket into rock where a screw pile cannot go.
Where they win: very high point loads, shallow rock sites, and deep founding where a poured element is preferred. Where they do not: they still need drilling, a cage, a pour and a cure, so they are slower and messier than screw piles; holes can collapse or fill with water in loose or wet ground and need lining; and steep sites can defeat rig access. Load testing, where wanted, is a separate cost.
What screw piles cost, and what drives the price
Screw pile cost is quoted per pile, not per square metre, and on a residential job the price is set by five things. Understand these and you can read any screw piers price with confidence, ours or anyone else's.
- Number of piles. Straight off the engineer's footing plan. This is the single biggest driver and it is set before anyone quotes.
- Design depth. Deeper founding means more steel, more extensions and more machine time. We quote to the depth in the soil report with an agreed rate per extra metre if the ground makes us go further.
- Pile size and load. A pile carrying a high point load is a heavier section with a bigger helix than one under a light bearer.
- Access and ground. Tight backyards, steep blocks, rock and hand-shifted equipment all add time. So does a site the machine cannot reach without matting.
- Travel. Inside our South East Queensland patch this is minor. Regional Queensland jobs carry a mobilisation cost, quoted up front.
On the cost of screw piles vs concrete, the honest answer is that the pile line item is rarely the whole comparison. Screw piles often price above bored piers on paper and land below them once you add excavation, spoil removal, formwork, concrete, pump hire, the cure days and the crew standing around waiting on them. Where solid rock sits shallow and access is easy, a bored pier can genuinely be cheaper. We will tell you when that is the case.
We do not publish a rate card, because a per-pile figure without your footing plan and soil report would be a guess. Send both and you get a quote against them, usually within one business day.
How to choose, in one line each
- Choose screw piles when the ground is reactive clay or deep sand, access is tight or the block slopes, the weather is against you, or your certifier wants a documented load per pile. This covers most South East Queensland residential sites.
- Choose bored piers when loads are very high and concentrated, or you need to socket into rock at depth, and the program can absorb a drill-cage-pour-cure sequence.
Comparison FAQs
Are screw piles cheaper than concrete bored piers?
It depends on the site. On reactive clay, sloping or tight-access blocks, screw piles are often cheaper once you count the drilling, spoil removal, cage, pour and program time that bored piers add. Where solid rock sits shallow, a bored pier can be the cheaper option. We quote against your soil report so the comparison is real, not generic.
Are screw piles as strong as concrete?
Yes, when engineered for the load. A screw pile's capacity is set by the engineer and proven by installation torque on every pile, which is a per-element load check that poured systems do not get as standard. Strength is a design outcome, not a material contest.
Why would I ever not use screw piles?
Mainly solid rock at shallow depth, ground full of obstructions, or very deep soft ground with no competent founding layer within reach. In those cases a bored pier is often the better answer, and we will tell you so. See when screw piles are the wrong choice.
Do screw piles get certified the same way?
They are installed to an engineer's design, and the depth and torque logged for every pile support the engineer's Form 43/12 certificate your certifier needs, with Form 15 on the design where required. More on that on our For Builders page.
Sources and standards referenced
- AS 2159: Piling: design and installation
- AS 2870: Residential slabs and footings
- Queensland Building and Construction Commission (QBCC): licensing and certification