What is Jack Pile Underpinning? Step-by-Step Process
When a building begins to show signs of foundation failure, such as cracks, leaks, and uneven flooring, it becomes essential to repair the foundation. The process of rebuilding and strengthening the already existing foundations is known as Underpinning.
The most common and widely used underpinning method is jack pile underpinning. This technique offers a fast solution for stabilising foundations, especially in urban areas with limited space.
In this blog, we will thoroughly explore jack pile underpinning, including its applications and its benefits. We will also discuss the process involved.
What is Jack Pile Underpinning?
Jack pile underpinning is a modern foundation strengthening technique that uses pre-cast concrete or steel piles for foundation support. These piles are driven into the ground beneath the already existing structure.
Once driven into the ground, these piles are connected to the building using specially designed brackets. After driving the piles to the required depth, a hydraulic jack is used to transfer the weight of the structure onto the piles.
Unlike traditional pilling, which requires extensive excavation and specialised equipment. Jack piles can be installed without digging the ground. The whole process involves minimal excavation and disruption, making it ideal for sites with limited access or sensitive surroundings.
When is Jack Pile Underpinning Used?
Jack pile underpinning is used when the existing foundation can no longer support the weight of the building. Some common scenarios include,
Foundation Subsidence
Foundation subsidence is caused by soil movement, shrinkage, and erosion due to leaked drains. Structural settlement can lead to cracks in walls, uneven floors, and misaligned doors and windows.
Jack piles are installed at key points, transferring the weight of the building to more stable strata and providing long-term support.
Increased Structural Load
If you are planning to add new floors or building extensions that exceed the original foundation capacity. You need to reinforce the existing foundations with jack piles to improve their strength and stability.
Structural Settlements
Soil movement, shrinkage, or nearby construction activity can cause vibration damage to the existing structure. Due to the ground settlement, one side of the building shrinks more than the other.
Failed Foundations
If the existing structure has poor foundation quality due to the usage of poor construction techniques, shallow footings, and weak materials. This results in weakening the foundation over time.
Jack piles act as new foundations, replacing the original foundation.
Sites with Limited Access
Jack piling is ideal for urban buildings with limited area. Due to sensitive surroundings and narrow roads, construction without extensive excavation is necessary.
With jack pile underpinning, we can reinforce the existing foundations without causing too much disruption and noise.
Factors Affecting the Cost of Jack Pile Underpinning
The price of a jack pile underpinning can vary depending on several factors,
- Number of piles
- Type of pile
- Pile material
- Site access
- Structural complexity
Jack Pile Underpinning | Step-by-Step Process
Jack pile underpinning is a highly controlled process designed to stabilise the existing structure of the building. During its installation, each step is carefully executed to minimise disturbance.
The whole process is carried out in the following steps.
Site investigation and planning
A structural engineer conducts a complete survey of the construction site. They analyse the soil conditions and the load distribution of the building. This step helps determine the cause of foundation failure, required pile depth, and the number of piles needed to support the foundation.
Pile Installation
Once the survey is completed, the piles are then driven into the ground vertically using pile drivers. These piles are installed until they reach the stable load-bearing stratum. The process is usually carried out by using hydraulic pile drivers, which work efficiently in areas with limited access.
Brackets and Jack Setup
Once the piles are positioned in their place, custom steel brackets are installed to connect the piles to the existing foundation. Hydraulic jacks are positioned between the brackets and pile heads to ensure smooth load transfer to the jack piles. The use of hydraulic jacks allows for a controlled and smooth transfer.
Load Transfer
After everything is in place, the hydraulic jacks carefully transfer the weight of the building from its weak foundations to new piles.
Permanent Securing
After the load is successfully transferred to the jack piles, the piles and brackets are locked in place using steel grout. This creates a new stable foundation to support the building in future.
Advantages of Jack Pile Underpinning
Jack piles are widely recommended as one of the most effective methods for underpinning due to their various advantages and characteristics. These benefits make this technique a top choice for property owners facing foundation issues.
- Minimal disruption
- Immediate stabilisation
- Load-bearing capacity
- Versatility
- Precise and controlled lifting
- Long-term stability
Limitations of Jack Pile Underpinning
Despite being the most effective and reliable underpinning method, jack piling may not be the right choice for every foundation repair. Before making a decision, property owners should thoroughly discuss all available options for underpinning with a structural engineer.
The major limitations of jack pile underpinning are,
- Higher cost
- Soil conditions
- Building load and design
- Equipment and expertise
- Timeframe and surrounding environment
Conclusion
Jack pile underpinning is one of the most reliable and precise methods for repairing and strengthening foundations. Its ability to provide immediate stabilisation, minimal disruption, and long-term structural support makes it an excellent choice for residential and commercial buildings.
However, it is essential to consider factors such as cost, soil conditions, and structural requirements before selecting this method. Consulting with a qualified structural engineer will help you choose the most suitable underpinning method for your property.
