Screw pile underpinning and traditional concrete underpinning are both viable methods for stabilising a Wagga home with a dropped footing, but they work differently, cost differently, and suit different site conditions. Three quotes for the same job that specify different methods will look very different on paper, and without a framework for comparing them, it is hard to know which is the better fit for your situation. This guide gives you that framework so the quote conversation with any contractor makes more sense.
The two methods in plain English
Concrete underpinning works by manually excavating pits beneath the existing footing and filling them with reinforced concrete. The new concrete extends the footing downward to a stable bearing stratum. It is a labour-intensive, time-consuming process that produces a significant volume of excavated spoil, but it uses well-understood materials, can be done entirely by hand in confined spaces, and has a long track record in Australian residential construction. A full description is in our concrete underpinning method guide.
Screw pile underpinning (also called helical pier underpinning) works by rotating a steel pile into the ground using a hydraulic machine. The helical flights on the pile bite into the soil as it rotates, driving the pile to depth without excavation. A bracket is then fitted to the pile and connected to the existing footing, transferring the load from the footing to the pile and down to the deeper bearing stratum. It requires machine access but produces minimal spoil and can reach bearing within the same day as installation.
Both methods address the same problem: a footing that is no longer bearing on stable soil. The choice between them depends on the specific site, structure and budget rather than on a universal preference for one over the other. Our underpinning service uses both methods and the site assessment determines which is specified. Traditional concrete underpinning also typically calls for temporary propping while a section of footing is excavated, worth understanding before comparing quotes between the two methods.
Side-by-side comparison table
| Feature | Screw pile underpinning | Concrete underpinning |
|---|---|---|
| Installation method | Machine-driven rotating pile | Manual excavation, concrete pour, cure |
| Typical installation time per pin | 1-3 hours | 1-2 days (plus 3-7 days cure time) |
| Soil spoil produced | Minimal | Significant (all excavated material) |
| Access requirement | Machine access (approx. 900 mm clearance) | Hand excavation possible in any access |
| Bearing depth achievable | Very deep (engineered to suit) | Typically 1-3 m; can be deeper with more labour |
| Load-bearing availability | Immediate after bracket installation | After concrete achieves design strength |
| Cost per pin | Typically higher (equipment, fabrication) | Typically lower in straightforward sites |
| Track record | Well-established in Australia, growing use | Decades of documented use |
| Concrete cure program | Not required | Required; drives project timeline |
These comparisons hold in general; actual site results vary. A concrete underpin in difficult access conditions may cost more than a screw pile on an open site. A screw pile that needs a specialist hydraulic rig on a site with narrow side access may cost more than expected once access works are included. Whichever method suits your site, how much of the footing actually needs treating (one corner versus the full perimeter) usually moves the total cost more than the method choice itself; our guide to partial vs full-perimeter underpinning explains how that scope decision gets made.
Bearing depth is one of the biggest factors behind these differences, since a deeper founding level generally means more excavation for a concrete underpin but comparatively little extra effort for a screw pile driven mechanically. Our guide to underpinning depth and how engineers decide founding level explains how that depth figure is actually determined for a given site.
Where screw piles win: speed, mess, access
Screw pile underpinning has clear advantages in three areas.
Speed: Because there is no concrete to pour and cure, a screw pile job can be installed and structurally loaded faster. On a four-bedroom home that might need twelve to sixteen pins, a screw pile installation can be completed in two to four days of active work. The equivalent concrete job might take three weeks once cure time is factored into the sequencing schedule. If the homeowner needs the work completed quickly, or if the project is time-sensitive (such as a pending property settlement), screw piles’ faster completion is a practical advantage. See how long does underpinning take for a more detailed breakdown of timelines.
Mess: Concrete underpinning produces excavated spoil that has to be managed, bagged and removed. On a site with established gardens, paved paths or limited vehicle access, this can create substantial disruption. Screw piles go into the ground without extraction: no pile of soil to cart away, no mixing concrete on-site, no bins needed for disposal. For homeowners who want minimal disruption to the property, this is a meaningful difference.
Access for the machine versus hand access: Where a small hydraulic machine can access the work area, screw pile installation is efficient. On sites with reasonable side access of around 900 mm or more, this is usually achievable with compact equipment.
Where concrete still wins: cost per pin, established track record
Concrete underpinning holds advantages that matter in many Wagga residential situations.
Cost per pin on straightforward sites: The materials are simple: concrete, steel reinforcement, manual labour. There is no proprietary equipment, no specialist fabricated pile, and no machine hire for each pin. On a site with straightforward access, moderate depths and uncomplicated geometry, the per-pin cost of concrete underpinning is typically lower than screw piles. The difference can be meaningful across a job with many pins, though the comparison shifts depending on project specifics.
No machine access required: Hand excavation is possible anywhere a person can work. Sites with very restricted access, sub-floor heights too low for machinery, or locations where a machine would cause unacceptable damage to surrounding surfaces are all served by concrete underpinning where screw piles would require access works or alternative approaches.
Established engineering documentation: Concrete underpinning has been used, tested, and documented in Australian residential construction for a long time. Design guidance is well-established, and certifiers are familiar with assessing and signing off on concrete underpin work. Screw pile underpinning is also well-documented and thoroughly used, but in some regulatory contexts the assessment path is more familiar with concrete.
Site conditions that rule one out
Some site conditions make one method clearly inappropriate.
Rock or cemented layers at shallow depth: Screw piles need to be torqued to depth without hitting an obstruction. Rock at 600 mm depth may stop a screw pile from reaching the designed bearing stratum. Concrete underpinning in this situation is simply excavated past the obstruction (with more effort and cost). If rock is present at a useful shallow depth, it can also serve as the bearing stratum for concrete underpins more directly.
Very restricted access: Where there is no machine access at all, screw piles are not practical. A concrete underpin can be excavated and poured by one person working in a confined sub-floor space.
Large-area poor ground: Where the problem isn’t one dropped corner but a broad zone of loose fill or unreliable bearing across much of the site, neither screw piles nor concrete underpins may be the most efficient answer; ground-improvement techniques like jet grouting or deep soil mixing are worth understanding for that narrower category of job.
Slab-on-ground with shallow void: Where the problem is a voided or settled slab rather than a failed strip footing, neither method may be ideal. Resin injection is often a better fit for that specific problem. See the resin injection underpinning guide for when that applies, and our guide to slab jacking injection patterns for how the void-filling and lift sequencing actually works once resin or grout injection is chosen.
Highly aggressive soils: Some soil chemistry can be aggressive to uncoated steel over very long periods. In most Wagga residential situations this is not a significant concern, but it is worth raising with the engineer if you know the site has unusual conditions.
What a Wagga specialist typically recommends and why
In practice, the method choice for a Wagga residential job depends on a few practical questions that a site assessment answers: How many pins are needed? What depth is required to reach stable bearing? Is machine access available? Is the project time-sensitive? Does the existing footing configuration suit a bracket system?
There is no universal correct answer between the two methods, and a contractor who insists one is always better regardless of site conditions may be reflecting their own equipment and expertise rather than what suits your site. A good assessment will explain the method recommendation in terms of the specific site conditions. Our foundation inspections service provides that unbiased assessment before any repair work is specified.
For an honest look at what underpinning does and does not achieve for wall cracks, see how underpinning actually fixes cracks before committing to either method. Once a method is chosen and the lift is underway, it’s also worth understanding what result to expect: our guide to re-levelling tolerances explains how “level” is realistically defined after the work is done.
FAQs
Is screw pile underpinning as good as concrete underpinning?
When correctly designed and installed to engineering specification, both methods provide reliable long-term bearing improvement. There is no basis for saying one is inherently more reliable than the other. The suitability depends on the site, soil, load requirements and other project-specific factors. Asking a specialist which method suits your specific situation is the right question.
How do I compare quotes that use different methods?
Focus on what each quote delivers in structural terms: the number of pins, the depth, the load capacity, the engineering basis and the warranty offered. Two quotes with different methods but the same outcome specification can be compared. Two quotes where one includes an engineer’s report and one does not, or where one specifies a structural engineering pin design and the other is based on a rule of thumb, are harder to compare fairly. See our underpinning cost guide for more on how to read quotes.
Do screw piles need maintenance over time?
Correctly specified and installed screw piles are designed as maintenance-free structural elements. The steel is typically coated or galvanised, and the load-bearing mechanism relies on mechanical engagement with the soil at depth rather than any surface-dependent property. Check what your specific contractor specifies for corrosion protection and confirm it suits the soil chemistry on your site.
Can screw piles be removed if needed?
Technically yes, screw piles can be rotated back out of the ground, unlike cast-in-place concrete underpins. In practice this is rarely done on completed residential work. The more relevant scenario is if a pile hits an obstacle during installation and needs to be repositioned, which is more straightforward with screw piles than with a half-poured concrete pin.
How long does screw pile underpinning take?
A typical residential job with six to sixteen pins can usually be completed in two to four days of installation work, with no cure time required. Mobilisation, access setup, bracket installation and reinstatement add some time beyond the pile installation itself. This compares to several weeks for a concrete underpinning job of similar pin count once cure time is included in the program.