When building starts to show signs of weakness in the foundation, such as cracks in walls, bumpy floors, and floors sinking, then engineers often go to underpinning. One of the most trustworthy and generally used techniques is called the needle and underpinning method.
The needle and pile underpinning method is a technique that is used to strengthen the existing building foundation, which needs extra support due to weak soil, structural fluctuations, and additional loads.
This method is precise and helps stabilise the building structure without causing disruption.
What is the Needle and Pile Method?
The needle-and-pile method consists of installing temporary horizontal needles and vertical piles to transfer the building’s weight to stronger soil below. It is an effective solution to reinforce the foundation, and stabilises the structure without major disruption.
The needle-and-pile method is a reliable technique for reinforcing the foundation of a structure when it begins to show signs of weakness, such as cracks in walls, uneven floors, or sinking.
How Does the Needle-and-Pile Underpinning Method Work?
This process follows a carefully controlled sequence to stabilise the structure while safely transferring loads to stronger ground beneath the existing foundations.
Inspection and Planning:
Engineers assess the structure to identify vulnerable areas and plan where to install the needles and piles.
Placing the Needles:
Horizontal needles are placed under the foundation walls to support the building while temporary piles are being installed.
Installing the Piles:
Concrete, steel, or timber vertical piles are driven into the ground beneath the needles to bear the building loads and solid soil.
Transferring the Load:
The weight from the building is transferred from the old foundation to the piles. This stabilises the structure and prevents further damage.
Removing Temporary Supports:
The needles are removed once the piles support the structure’s weight. The structure’s foundation is now reinforced to handle the load properly.
When is Needle and Pile Underpinning Used?
The needle and pile underpinning method is commonly used when:
- The foundation of structures becomes weak over time.
- The soil started shifting or settling roughly.
- Extra floors increase the building’s weight.
- Nearby construction or digging can affect the stability of the building.
- There is a need to dig deeper or lower into the basement.
Advantages of Needle and Pile Underpinning
Needle and pile underpinning offers a practical, efficient solution for strengthening existing foundations, particularly where site conditions or structural constraints limit traditional underpinning methods.
Suitable for Crowded and Restricted Sites
Needle and pile underpinning is well suited to confined or built-up areas, allowing structural support work to be carried out with minimal excavation and limited disruption to surrounding buildings.
Provides Strong and Reliable Structural Support
This method transfers structural loads to deeper, stable ground using steel needles and piles, ensuring long-term stability and preventing settlement in existing residential or commercial buildings.
Adaptable to Different Soil Conditions and Structures
Needle and pile underpinning can be designed for varying soil types and building layouts, making it a flexible solution for complex ground conditions and diverse structural requirements.
Faster Installation Compared to Traditional Methods
With reduced excavation and a controlled installation process, needle and pile underpinning is quicker to complete than traditional methods, helping minimise disruption and project downtime.
Conclusion
The needle-and-pile underpinning method is practical and the best solution for strengthening the foundation of an existing building. By transferring the load to deeper, more stable soil layers using a combination of needles and piles, it ensures long-term structural safety without damaging the existing structure.
