Underpinning is the process of re-supporting a settled or damaged foundation by installing new engineered piers beside the existing footing and connecting them with brackets, transferring the load to stable ground below the movement zone. Screw piers are one of the principal systems used for underpinning in South East Queensland's reactive clay, because they install without the extended excavation that older underpinning methods need. Core Screw Piling installs underpinning piers across the Gold Coast, Brisbane and the Sunshine Coast up to Noosa, always to a structural engineer's design. For the broader method, see our guide to what screw piling is and how it works.
Signs you may need underpinning
Most homes in reactive clay areas show some hairline cracking over the years; that alone is not a red flag. What is worth investigating:
- Doors and windows that stick or no longer latch cleanly, especially if the problem is new or getting worse.
- Cracks wider than a few millimetres, particularly stepped cracks in brickwork or cracks that reappear after patching.
- Floors sloping toward one corner or a visible gap opening between a wall and the floor or ceiling.
- Movement following drought-flood cycles, common in South East Queensland's reactive clay after a dry spell breaks with heavy rain.
- Gaps appearing around external stairs, verandahs or attached structures pulling away from the main dwelling.
None of these confirm underpinning is needed on their own. They are reasons to get a structural engineer's assessment, not reasons to book a piling contractor directly.
How screw pier underpinning works
Once an engineer has assessed the movement and specified a remediation design, screw piers are installed immediately beside the affected section of footing. Each pier is wound in to the design depth with torque monitored throughout, then connected to the existing footing with an engineered bracket. Depending on the design, the structure may also be jacked back toward level before the brackets are locked off.
Because the piers install beside the existing footing rather than replacing it outright, underpinning is usually far less disruptive than it sounds: there is no need to demolish the existing slab or footing, and most residential underpinning jobs are completed without the household needing to move out.
Why the engineer comes first, not the piling contractor
Underpinning always starts with a structural engineer's assessment, never with a contractor arriving to sell you piers. The engineer's job is to work out why the movement is happening (soil reactivity, drainage, tree roots, a leaking pipe) and whether underpinning is actually the right fix, since treating the cause sometimes matters as much as reinforcing the footing. Only once that assessment and design exist do we install to it.
If you contact us directly about visible cracking, we will point you to an engineer's assessment before quoting anything. We are happy to recommend engineers we work with regularly if you do not already have one.
What the process looks like on site
Structural engineer's assessment
Confirms the cause of movement and specifies whether underpinning is the right remediation, and to what design.
Your quote from the design
We price the pier count, depth and bracket type the engineer has specified.
Installation
Piers are wound in beside the affected footing with torque monitored on every one, and connected via engineered brackets.
Certification and handover
Installation records support the engineer's sign-off, giving you documented proof for insurance, resale or council purposes.
What underpinning costs
Underpinning cost depends on how many piers the engineer's design calls for, the depth needed to reach stable ground, access around the affected section of the house, and whether re-levelling is included alongside the piers themselves. It is priced per project rather than as a flat rate, because every remediation design is different. Our screw piling cost guide covers the general cost factors that apply across all our residential work.
Underpinning FAQs
Will underpinning stop the cracks appearing again?
Underpinning addresses the foundation's ability to carry load on stable ground, which is usually the core fix. If the underlying cause (drainage, tree roots, a leak) is not also addressed, movement elsewhere on the same structure is still possible. This is exactly why the engineer's assessment covers cause as well as remediation.
Do I need to move out during underpinning work?
Most residential underpinning is completed with the household still living in the home, since piers install beside the footing rather than requiring the structure to be lifted or the slab removed. Your engineer's specific design will flag it if your situation is an exception.
Is underpinning covered by home insurance?
It depends on your policy and the cause of the movement; this is a question for your insurer or broker, not your piling contractor. A documented engineer's assessment is usually the first thing an insurer will ask for, which is another reason to get that assessment before any remediation work begins.
How do I know if it's underpinning or just normal seasonal movement?
Minor, stable hairline cracking is common in reactive clay areas and often is seasonal. Widening cracks, sticking doors that are getting worse, or a visibly sloping floor are worth a professional look. A structural engineer can tell the difference; we cannot make that call from a phone description.
Can underpinning be done on a sloping block?
Yes. Screw piers are well suited to sloping and difficult-access sites generally, since installation plant is compact and does not need the benching a dug footing would require. See our guide to sloping and difficult site foundations.