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What Are Screw Piles and How Do They Work?
Updated: Sep 22
Screw piles are steel foundation piles fitted with one or more helical plates that are rotated into the ground to support a structure. They work by transferring structural loads through weaker near-surface soil into stronger ground below.
Unlike traditional concrete foundations, screw piles do not normally require large excavations or a curing period. They are installed using hydraulic torque equipment, and the resistance encountered during installation can be measured to help assess the pile's load-bearing capacity.
At ABC Anchors, we offer a range of screw pile specifications to suit different requirements. If you are already comparing options for your project, see our main screw piles page for detailed technical information.
What Is a Screw Pile?
A screw pile, also commonly called a helical pile, is a steel shaft with one or more helical plates welded to it.
The helix performs two important functions.
First, it helps the pile advance into the soil as the shaft is rotated.
Second, once the pile reaches the required installation conditions, the helix transfers structural loads into the surrounding ground.
Screw piles can therefore act as deep foundation elements beneath buildings and other structures.
Rather than depending only on the soil directly beneath a shallow footing, the pile can extend deeper until the required resistance is achieved.
At ABC Anchors, we have a wide range of screw piles available for different foundation requirements.
How Do Screw Piles Work?
Screw piles work by combining the steel pile shaft, helical plates and surrounding soil to support structural loads.
During installation, a hydraulic torque head rotates the pile into the ground.
As the helix moves through the soil, the installer monitors how much rotational resistance the pile encounters.
Where resistance is low, the pile may continue deeper.
Where the required installation criteria are achieved, the torque reading provides important information about the performance of the installed pile.
The pile is then connected to the structure using the appropriate termination, bracket or foundation detail.
This allows structural loads to be transferred from the building into the pile and then into suitable ground.
How Are Screw Piles Installed?
Screw piles are installed using specialist hydraulic equipment.
Depending on the project, this may include:
handheld torque heads
excavator-mounted torque heads
suitable adaptors
torque monitoring equipment and
the required pile extensions and terminations
The pile is positioned at the designed installation point and rotated into the ground.
Additional shaft sections can be connected where greater depth is required.
Installation continues until the design requirements are achieved.
At ABC Anchors, we offer both handheld and excavator-mounted screw pile installation equipment.
Handheld equipment can be particularly useful where access is restricted, while larger excavator-mounted torque heads can be used for higher-capacity piles and more accessible sites.
Why Is Installation Torque Important?
One of the most useful features of screw piling is that installation torque can be monitored as each pile is installed.
Torque is the rotational force required to turn the pile through the soil.
As soil resistance increases, more torque is generally required to continue installation.
This relationship allows engineers and installers to use measured installation torque when assessing pile capacity.
ABC Anchors uses the recognised relationship:
Qu = Kt × T
where:
Qu is the ultimate pile capacity
Kt is the empirical torque factor and
T is the average installation torque
Appropriate design and safety factors are then applied when determining the allowable or safe working load.
For the full technical explanation, see our guide to screw pile torque and load calculations.
What Are Screw Piles Used For?
Screw piles can be used for a wide range of foundations.
Common applications include:
residential buildings
commercial buildings
house extensions
underpinning and foundation repairs
bridge foundations
temporary structures
structures near tree roots
modular buildings
solar installations
wind turbine foundations and
other specialist foundation projects
The correct pile depends on the structural loads, ground conditions, access and foundation design.
You can explore the different uses in more detail on our screw pile applications and solutions page.
What Are the Benefits of Screw Piles?
Screw piles can offer several practical advantages where they are suitable for the project.
Reduced excavation
Screw piles are rotated directly into the ground, which can reduce the amount of excavation required compared with many traditional foundation systems.
Little spoil to remove
Because the pile displaces or moves through the soil rather than requiring a large foundation trench, considerably less excavated material may need to be removed from site.
No concrete curing period
A correctly installed steel screw pile does not need to wait for concrete within the pile to cure before it can support structural loads.
Low vibration installation
Screw piles are rotated into the ground rather than repeatedly driven using impact equipment. This can make them useful where vibration around neighbouring structures needs to be controlled.
Suitable for restricted access
Handheld installation equipment can allow screw piles to be installed in areas that larger piling rigs cannot easily reach.
Installation can be measured
Torque readings provide useful information during installation and can be recorded for individual piles.
Removable in some applications
Depending on the design and condition of the pile, screw piles used for temporary structures may be capable of being removed by reversing the installation process.
Screw Piles vs Concrete Foundations
Traditional concrete foundations and screw pile foundations support structures in different ways.
A conventional shallow concrete foundation normally requires excavation before concrete is poured into the prepared trench or footing.
The concrete must then achieve sufficient strength before later construction stages can proceed.
A screw pile is instead installed directly into the ground and transfers loads through its shaft and helical plates.
Because it is a manufactured steel foundation element, it does not rely on a large volume of freshly poured concrete curing in the ground.
However, that does not mean screw piles are automatically the correct foundation for every project.
Ground conditions, structural loading, access, engineering requirements and the proposed building all need to be considered before the foundation system is selected.
For a wider comparison of foundation methods, see our guide to understanding the different types of piling.
How Deep Do Screw Piles Go?
There is no single standard screw pile depth.
The required installation depth depends on factors including:
ground conditions
soil strength
structural loading
pile size
helix configuration
design requirements and
installation torque
Some projects may reach the required resistance relatively close to the surface, while others may require piles to extend considerably deeper.
Pile extensions can be added during installation where additional depth is needed.
If depth is one of your main concerns, read our guide to how deep screw piles need to go.
Do Screw Piles Work in Difficult Ground?
Screw piles can be used in a wide range of ground conditions, but the design needs to reflect the actual soil profile.
Ground investigation may identify:
clay
loose or dense granular soils
made ground
variable strata
groundwater
obstructions or
stronger bearing material at greater depth
The pile diameter, helix configuration and installation depth can then be selected accordingly.
Where unusually dense or rocky ground is present, specialist pile tips or alternative installation methods may be required.
A ground investigation is therefore an important part of more demanding projects.
See our soil investigation and pile testing page for further explanation of the process.
Are Screw Piles Suitable Near Trees?
Screw piles can be useful for some projects near trees because they require less excavation than conventional trench foundations.
This can help reduce disturbance where tree roots and Root Protection Areas need to be considered.
The pile locations and installation method still need to be designed around the specific site, tree constraints and structural requirements.
For more information, see our screw pile foundations near tree roots guidance.
Can Screw Piles Be Used for Extensions?
Yes.
Screw piles can be used to support house extensions where the foundation design and ground conditions make them appropriate.
They can be particularly useful where:
access is limited
excavation would be difficult
tree roots are present
ground conditions vary
minimising spoil is important or
the project programme benefits from avoiding a concrete curing period
See our dedicated guidance on extension foundations using screw piles.
Can Screw Piles Be Used for Subsidence and Underpinning?
Yes.
Screw piles can form part of an engineered underpinning system where an existing foundation requires additional support.
The piles can be installed beside or beneath the affected foundation and connected using suitable underpinning brackets and structural details.
Loads can then be transferred away from unsuitable near-surface soil into more stable ground below.
Where you are dealing specifically with foundation movement or subsidence, go directly to our screw pile underpinning and foundation repairs page for further information on suitable solutions.
Which Screw Pile Do I Need?
The correct screw pile cannot be selected purely from the size of the structure.
Pile selection depends on:
structural loads
ground conditions
required pile capacity
installation torque
pile depth
access
corrosion requirements
termination details and
the engineering design
At ABC Anchors, we manufacture several screw pile systems for different requirements. Our main screw piles page provides details of the current range and is a useful starting point when comparing specific pile sizes and technical specifications.
From Understanding Screw Piles to Planning a Project
If you started here simply wanting to know what screw piles are, the basic principle is straightforward:
a steel pile with helical plates is rotated into the ground, installation resistance is measured, and the completed pile transfers structural loads into suitable soil.
The next step depends on what you need to know.
For pile sizes and specifications, go to screw piles.
For the relationship between installation torque and capacity, read calculating torque and load.
For specific uses, explore screw pile applications and solutions.
For machinery, see screw pile installation equipment.
For a project-specific enquiry, contact ABC Anchors or call +44 (0)1380 850885.
Frequently Asked Questions About Screw Piles
1. What are screw piles?
Screw piles are steel foundation elements fitted with one or more helical plates. They are rotated into the ground and used to transfer structural loads into suitable soil below the surface.
2. Are screw piles the same as helical piles?
Yes. The terms screw pile and helical pile are commonly used to describe the same general type of foundation pile, although individual designs and specifications can vary.
3. How do screw piles work?
Screw piles work by transferring structural loads through the pile shaft and helical plates into surrounding soil. They are rotated into the ground until the required installation conditions and resistance are achieved.
4. How are screw piles installed?
Screw piles are installed using hydraulic torque heads. These can be handheld or mounted to excavators depending on the pile size, required installation torque and available site access.
5. Why is torque important when installing screw piles?
Installation torque indicates the resistance encountered by the pile as it advances through the ground. This can be related to ultimate pile capacity using an appropriate empirical torque factor.
Read more about screw pile torque and load calculations.
6. Do screw piles need concrete?
The screw pile itself does not normally require concrete to form the pile. However, the completed foundation system may incorporate concrete, steel beams or other structural elements depending on the design.
7. Do screw piles need time to cure?
No. A steel screw pile does not require a concrete curing period before it can accept structural loads once it has been correctly installed and connected.
8. How deep do screw piles go?
There is no standard depth for every project. Screw pile depth depends on the ground conditions, required load capacity, pile specification and resistance achieved during installation.
9. Can screw piles be used for house extensions?
Yes. Screw piles can be used for extension foundations where the structural design and ground conditions make them suitable.
10. Can screw piles be installed near trees?
They can be suitable for some projects near trees because installation requires relatively little excavation. Tree roots, Root Protection Areas and the site-specific foundation design still need to be considered.
11. Can screw piles be used for underpinning?
Yes. Screw piles can form part of an engineered underpinning system for stabilising foundations affected by subsidence or other forms of movement.
See our dedicated underpinning and foundation repairs page for more detail.
12. What can screw piles be used for?
Applications can include houses, extensions, commercial buildings, temporary structures, bridge works, underpinning, renewable energy installations and other engineered foundation projects.
See our full screw pile applications and solutions section.
13. How do I choose the right screw pile?
The correct pile depends on the structural loads, ground conditions, required capacity, installation depth, torque, access and engineering design. For specific sizes and technical information, visit our main screw piles page.
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