Cracks in your walls, sinking floors, and doors that jam for no apparent reason, these are more than just cosmetic annoyances. They can be the first signs of a deeper structural issue: foundation problems. When left unaddressed, these symptoms can lead to costly and sometimes dangerous outcomes.
Underpinning is a proven method used to stabilise and re-support foundations affected by subsidence or movement. Acting early is critical; the longer you wait, the more extensive (and expensive) the damage can become.
This guide will walk you through two common underpinning methods: traditional concrete underpinning and modern resin injection, like the one we use here at Resinject, to help you make an informed decision for your home.
Understanding Foundation Problems
Foundation movement or subsidence can be caused by several factors, including:
- Soil shrinkage and swelling: Expansive clay soils contract when dry and swell when wet, putting pressure on foundations.
- Tree roots: Large trees near a home can draw moisture from the soil, leading to uneven settling.
- Moisture variation: Poor drainage, leaking pipes, or extreme weather changes can alter soil stability.
When these shifts occur, the foundation may sink or become uneven, leading to structural damage. That’s where underpinning comes in, strengthening and re-stabilising the foundation by extending its support.
Early warning signs include:
- Cracks in brickwork or internal walls
- Gaps around windows or doors
- Uneven floors
- Doors and windows that stick or won’t close
- Hollow sounding floors
Catching these signs early allows for a more straightforward, less costly repair.
Concrete Underpinning (The Traditional Approach)
How it works:
Concrete underpinning involves excavating beneath the existing foundation in sections and pouring new concrete footings to a deeper level. The process is sequential, often taking several weeks depending on the size of the area.
Typical use cases:
- Older buildings with stable access
- Sites where excavation is straightforward
Advantages:
- Established and widely understood method
- Over a century of historical use
Disadvantages:
- Disruptive: involves heavy excavation and machinery
- Time-consuming: can take weeks to complete
- Expensive due to high labour and material costs
- Often not recommended for homes on reactive clay soils (per AS2870 standards)
Resin Injection Underpinning (The Resinject Way)
How it works:
Resinject’s resin injection technique is a modern, non-invasive alternative. Expanding structural resin is injected into the ground beneath the affected areas. As the resin expands, it compacts and strengthens the soil, lifting and re-supporting the structure above. This process is monitored in real-time using precision laser levels to ensure accurate, controlled lifting.
Customisation:
Resinject uses specially formulated resins tailored to suit specific ground conditions, including reactive clay, sandy soils, and unstable fill.
Advantages of Resin Injection with Resinject:
- No excavation required – clean and non-disruptive
- Typically completed in 1 day
- Homeowners usually don’t need to vacate the property
- More cost-effective due to reduced labour and faster execution
- 30+ years of proven results globally
- Environmentally friendly materials
- Effective in a wide range of soil types, including reactive clays
Side-by-Side Comparison Table
| Feature | Concrete Underpinning | Resin Injection (Resinject) |
|---|---|---|
| Method | Excavation & concrete footings | Expanding structural resin injection |
| Time Required | Several weeks | 1 day |
| Mess/Disruption | High | Minimal |
| Cost | Typically higher | More cost-effective |
| Suitability | Limited by soil type | Suited to wide range of soils |
| Proven Performance | 100+ years | 30+ years globally |
Cost of Underpinning in Australia
Several factors can influence the cost of underpinning:
- Site access and location
- Soil conditions and reactivity
- Severity and spread of subsidence
- Method used (excavation vs resin)
Why resin injection is usually more cost-effective:
- Less manual labour required
- Quicker turnaround = lower disruption
- No need for excavation or heavy machinery
Typical pricing:
While prices vary, resin injection often falls between $4,000–$15,000+, depending on scope. Traditional concrete underpinning can significantly exceed that due to longer timeframes and higher labour requirements. If you need more information, you can check out our guide on the cost of underpinning your home.
Why More Homeowners Choose Resinject
With thousands of successful projects completed across Australia, Resinject has become a trusted name in foundation repair. Our solutions are recommended by structural engineers, strata managers, and builders alike.
- 100+ years combined experience
- Remediated over 14,000 buildings
- Certified Licensed Builders
- ISO Certified 9001, 14001, 45001
- Australian Certified Resin
- 50 year product warranty
When you choose Resinject, you’re choosing peace of mind.
Conclusion
Foundation issues shouldn’t be ignored, and when it comes time to act, knowing your options is crucial. While traditional concrete underpinning has been around for over a century, modern resin injection offers a faster, cleaner, and often more cost-effective solution. At Resinject, we specialise in non-invasive foundation repairs that stand the test of time. If you’re seeing signs of subsidence, don’t wait, reach out to contact our team for a no-obligation site assessment.
Protect your home. Secure your foundation. Choose Resinject.
FAQs
What is resin injection underpinning?
A modern method of stabilising foundations by injecting expanding structural resin into the ground, which lifts and re-supports the structure.
Is resin injection safe and permanent?
Yes. It has a 30+ year global track record and is considered a long-term solution when performed by experts.
How long does it last?
Properly applied resin injection lasts for decades and resists weather and soil movement. Resinject has a 50 year product warranty.
Will I need to move out during the process?
No. Most homeowners stay in their home while work is carried out, it’s that non-invasive.
Is it suitable for clay soil?
Absolutely. Resin injection is especially effective for reactive and unstable clay soils.
What’s the difference between chemical and resin underpinning?
They are often used interchangeably. “Chemical” refers to the engineered resin used to stabilise soil beneath structures.
