If you’re having any kind of groundworks construction, it’s important that you discuss it with a qualified piling contractor so that you understand which piling method will work best.
The piling method that works best for your project can depend on several factors, including available space, ground conditions and how much noise or vibration the site can tolerate.
One of the most commonly used foundation methods in these situations is CFA piling. This guide explains what CFA piling is, how it works, when it should be used, and when an alternative foundation solution may be more suitable.
What Is CFA Piling?
CFA piling is a bored piling method used to form reinforced concrete foundations with minimal noise and vibration. It’s widely used across residential, commercial and urban construction projects where ground stability and installation control are essential.
A CFA pile is installed using a Continuous Flight Auger, which drills into the ground to the required depth. Concrete is pumped through the hollow stem of the auger as it’s withdrawn, forming the pile in one continuous operation. Steel reinforcement is inserted immediately after concreting to achieve the required structural capacity.
What does CFA stand for?
CFA stands for Continuous Flight Auger. The term refers to the single, continuous auger used during installation, which supports the surrounding soil and helps reduce the risk of bore collapse.
Because of this process, CFA piling is almost vibration free and is one of the quieter piling methods available. This makes it well suited to built-up or environmentally sensitive areas.
CFA piling can be used in a wide range of ground conditions, including:
- Sand
- Gravel
- Silt
- Clay
- Soft rock
CFA piles are also known as auger cast piles, screw piles and augered cast-in-place piles (ACIP). It is a non-displacement system, meaning that the soil excavated from the pile is brought to the surface. CFA piles were developed in the USA in the 1940s, were first used in the UK in the 1960s and were introduced to Europe in the 1970s with the invention of the first hydraulic piling rigs.
How Does CFA Piling Work?
Continuous Flight Auger piling is a cast in-situ process and piles are constructed using a hollow stem continuous flight auger.
Drilling the pile
A piling rig fitted with a continuous flight auger drills into the ground to the required depth. The auger remains in place during drilling, supporting the surrounding soil and reducing the risk of collapse in loose or variable ground conditions.
Placing the concrete
While the concrete is poured the auger is extracted in a rotating motion so as to remove the ground material. When the concrete extends to ground level, a steel reinforcement cage is then plunged into the wet concrete.
Filling the bore from the bottom up helps:
- Prevent voids forming
- Maintain consistent pressure
- Ensure the pile is fully formed
Installing reinforcement
Steel reinforcement is placed into the fresh concrete to meet the structural engineer’s design requirements and load calculations.
Quality control during installation
Experienced piling contractors monitor key installation data, including drilling depth, concrete volume, auger withdrawal rate and concrete pressure. This level of quality control is essential to ensure long-term pile performance.
As technology advances, piling rigs get more sophisticated. CFA piling rigs are now often equipped with computer displays that show the drilling and concreting parameters, as well as the speed of rotation and penetration during the drilling phase. This helps to monitor, control and record the installation process.
When to Use CFA Piles
CFA piling is often specified where site conditions and programme requirements make other piling methods less suitable.
Ground conditions suitable for CFA piling
CFA piles perform well where the bore needs continuous support during installation, including:
- Sand and gravel
- Silt
- Clay
- Made ground
- Soft rock
Site and project conditions where CFA piling works well
CFA piling is commonly used on sites where:
- Low noise and vibration are required
- Existing buildings are close by
- Ground movement needs to be controlled
- Installation speed is important
Typical applications
CFA piling is often recommended for:
- Commercial developments
- Residential blocks and housing schemes
- Urban construction sites
- Projects with tight programme constraints
Early advice from a structural engineer and piling contractor helps confirm suitability.
When CFA Piling May Not Be Suitable
CFA piling isn’t the right solution for every site, and understanding its limitations early can reduce risk.
Ground conditions that can limit CFA piling
CFA piling may be less suitable where:
- Ground conditions are very loose or highly variable
- Large obstructions or buried structures are present
- Excessive groundwater flow can’t be properly controlled
Site constraints to consider
Practical limitations may include:
- Restricted access that won’t allow a CFA piling rig
- Limited headroom beneath existing structures
- Insufficient working space for safe rig operation
A site assessment and ground investigation are essential before finalising the piling method.
What are the advantages of CFA piles?
This type of piling system has a lot of benefits, including:
- This type of piling method is free from significant vibration and noise so it has low levels of disruption.
- The installation is quick compared to other piling methods.
- When used on a large scale it can be very economical.
- They can be used for a range of challenging ground conditions.
- They have depths of beyond 35m and diameters ranging from 450mm to 1200mm.
Are there any disadvantages of CFA piles?
Although there are a lot of benefits to using CFA piles, there are a few circumstances in which they would be less likely to be used. Some disadvantages of CFA piles include:
- If you’re using them on a small scale they aren’t very economical
- They are not recommended for alternating hard and soft ground layers or changing strata.
- There is a limited capacity for bending moments or lateral and tension forces
When are CFA piles used?
CFA piles can be made as single piles or as part of a pile group (similar to driven foundations). They are commonly used for multi-story building, large structural foundations and bridges.
What to Do Next: Get in Touch
If you’re looking for a piling contractor, give us a call.
We are equipped to assess, design and install various types of piling foundations for a range of building types.
If you’d like to talk to a member of our team about what to do next, give us a call on 08002061563 or fill out our contact form to request a response.