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What do you call Screw Piles, Helical Piles and Ground Anchors?
Updated: 1 hour ago
Helical Screw Piles, Screw Piles and Ground Screws Explained
Screw piles and helical piles are different names commonly used for steel foundation piles with helical plates that are rotated into the ground. You may also hear terms such as helical screw piles, screw anchors and ground screws. The terminology varies according to the product, application and whether it is being used as a foundation or anchor.
At ABC Anchors, we design and manufacture screw pile systems for projects across the UK. But if you are researching foundations for the first time, the different terminology can make a relatively straightforward concept sound much more complicated than it is.
This guide explains what screw piles and helical piles are, how they work, how they are installed, what loads they can carry and where screw pile foundations can be used.
What Are Helical Screw Piles?
Helical screw piles are steel foundation elements that are rotated into the ground rather than driven with impact or installed within an excavated concrete foundation.
The pile consists of a steel shaft with one or more helical plates, sometimes called helices or flights. As torque is applied to the pile, these helices help it advance into the ground.
Once the required installation conditions have been achieved, the top of the pile can be fitted with a suitable termination to connect it to the structure above.
The principle explains several of the names used for the system:
Screw pile describes the way the pile is rotated or screwed into the ground.
Helical pile describes the helical plates attached to the pile.
Helical screw pile combines the two descriptions.
ABC Anchors' standard screw pile range includes shaft diameters from 60 mm to 89 mm, excluding the helices, with different pile specifications available according to the project requirements.
Are Helical Piles and Screw Piles the Same Thing?
In foundation construction, helical piles and screw piles generally describe the same type of foundation technology.
The terms focus on different characteristics of the pile rather than fundamentally different foundation principles.
"Helical pile" refers to the helix or helices attached to the steel shaft. "Screw pile" refers to the rotational installation method.
You may also encounter:
Helical anchors – generally associated with applications where the element is being used to provide anchorage rather than primarily supporting structural loads.
Screw anchors – another term commonly associated with resisting anchoring or uplift forces.
Helical tiebacks – helical elements used in lateral applications, such as supporting retaining structures.
Ground screws – a related term frequently encountered in applications such as lightweight structures and renewable energy installations.
The exact terminology therefore matters less than the engineering requirement. The pile or anchor must be selected and designed for the loads, structure and ground conditions involved.
What Is a Helical Pile Foundation?
A helical pile foundation uses multiple helical piles to transfer loads from a structure into suitable ground.
Instead of excavating conventional foundations and filling them with concrete, piles are installed at predetermined positions. Suitable terminations then provide the connection between the piles and the structure.
The number, diameter, length and arrangement of piles cannot simply be chosen from the size of the building.
A structural engineer needs to establish the loads that the foundation must support.
Ground conditions also need to be considered so that an appropriate pile specification can be developed.
ABC Anchors recommends considering a test screw pile before committing to a full order. Our test installation can provide useful information about ground conditions and pile performance, although ground conditions can still vary across an individual site.
Read more about the complete screw pile process, from structural engineering and site information through to installation.
How Do Screw Pile Foundations Work?
A screw pile foundation works by transferring structural loads through the piles into the surrounding ground.
During installation, a torque motor rotates the pile. The helical plates allow it to advance as resistance from the ground increases.
One of the important parts of this process is installation torque.
Torque provides information about the resistance being encountered as the pile travels through the soil. The pile must achieve the torque required by its design as part of demonstrating that it can provide the required performance.
Torque is monitored during installation rather than simply installing every pile to an assumed depth.
ABC Anchors explains the relationship between ultimate pile capacity and installation torque using:
Qu = Kt × T
where:
Qu is the ultimate pile capacity;
Kt is the empirical torque factor; and
T is the average installation torque.
The appropriate pile design, target torque, depth and safe working load are project-specific and should be determined from the relevant engineering information.
For a more detailed explanation, see our guide to calculating screw pile torque and load.
How Are Screw Piles Installed?
Screw piles are installed using rotational torque rather than hammering them into the ground.
The project should begin before the first pile reaches site.
A structural engineer assesses the building design and expected loads so that the required pile type, size and quantity can be established. Information about the ground is also important, and a soil investigation or test pile may form part of this process.
Pile locations can then be set out according to the foundation design.
During installation, a hydraulic torque head rotates each pile into the ground. Depending on pile size, site access and the project, equipment can include handheld or excavator-mounted torque heads.
Installation torque is monitored as the pile advances.
If the required installation conditions have not been achieved, extensions can be added where specified so that the pile can continue to the necessary depth and ground resistance.
When installation is complete, an appropriate termination connects the pile to the structure.
Because the process does not depend on concrete curing, ABC Anchors screw piles can accept their specified loads immediately after installation.
How Much Load Can Helical Screw Piles Carry?
There is no single load capacity that applies to every helical screw pile.
Capacity depends on factors including:
pile diameter and specification;
helix configuration;
installation torque;
soil conditions;
pile depth;
whether loads are in tension or compression; and
the project's required factor of safety.
This is why a screw pile should not be selected simply by finding a generic load figure online.
ABC Anchors' pile systems are available in different sizes and torque capacities, and its published design loads can be accepted in either tension or compression where the pile has been correctly specified and installed.
A structural engineer should establish the project loads and appropriate design requirements.
During installation, torque readings provide an important means of checking pile performance against the specification. These readings should be recorded, particularly where information is required for Building Control, engineers or warranty providers.
Where Are Screw Pile Foundations Used?
Screw pile foundations can be used across a broad range of construction and civil engineering applications.
New Build Foundations
Screw piles can provide foundations for new structures where they have been designed for the building loads and site conditions.
The piles are positioned according to the structural design and connected to the building through appropriate terminations or foundation components.
Find out more about screw piles for new build foundations.
Extensions
House and building extensions can present foundation challenges where access is restricted or where excavation needs to be minimised.
The availability of different installation equipment means screw pile systems can be considered for projects where conventional piling machinery may be impractical.
See our information on screw pile foundations for extensions.
Underpinning and Foundation Repairs
Screw piles can also form part of an engineered underpinning or foundation repair solution.
In these applications, the purpose is to provide support to an existing structure, so the cause of the foundation problem and the loads involved need to be properly assessed before a repair system is designed.
Learn more about underpinning and foundation repairs.
Tree and Root Protection Areas
Traditional excavation can become particularly challenging where foundations are required near trees.
Screw piles have relatively small shaft diameters and do not require continuous foundation trenches, allowing foundation layouts to be developed around site constraints where appropriate.
Read about building around tree roots.
Bridges and Infrastructure
Helical pile foundations can also be engineered for bridge and infrastructure projects.
As with any larger structural application, pile selection depends on the loads, ground investigation and project-specific engineering requirements.
See our bridge foundation applications.
Temporary Structures
A screw pile is mechanically installed rather than cast permanently in concrete. Depending on its condition, specification and application, it may therefore be possible to remove a pile by reversing the installation process.
This can make screw piles relevant to certain temporary works where a removable foundation solution forms part of the design.
Find out more about screw piles for temporary structures.
Solar Panels and Wind Turbines
Ground-mounted solar arrays and some wind energy installations require foundations capable of resisting both structural and environmental loads.
Screw pile and ground screw systems can provide an alternative foundation approach where they are appropriately engineered for those loads and site conditions.
What Are Ground Screws?
Ground screws are another type of steel foundation element installed into the ground by rotation.
The term overlaps with screw pile terminology and is sometimes used broadly, particularly for renewable energy and lighter structural applications. However, it should not automatically be assumed that every product described as a ground screw has the same dimensions, load capacity or intended use as an engineered helical screw pile.
The important questions are not simply what the product is called, but:
What loads must it carry?
What are the ground conditions?
What pile or screw specification is required?
How will it connect to the structure?
What installation torque or other verification is required?
For structural foundations, these questions need to be answered through the design and specification rather than terminology alone.
What Are the Advantages of Screw Piles?
The practical characteristics of screw piles can make them suitable for projects where excavation, access, installation time or ground disturbance needs to be considered.
No excavation for the pile itself: The pile is rotated directly into the ground, so screw piling does not require excavation around the pile during normal installation. This also means there is no excavated spoil from the pile installation requiring muckaway.
Low noise and vibration: ABC Anchors piles are installed with a torque motor. They do not require the hammering or vibratory driving associated with some other piling systems.
Immediate loading: Once correctly installed and terminated, the piles can accept their specified loads without waiting for concrete to cure.
Tension and compression: ABC Anchors screw piles can be designed to accept published loads in tension or compression, allowing them to address downward structural loads as well as uplift requirements where correctly specified.
Different installation angles: Piles can be installed at angles where required by the engineering design.
Restricted-access options: Handheld torque heads can be used with appropriate piles where site access makes larger equipment difficult to use. Machine-mounted systems are available for larger pile sizes and other installation requirements.
These characteristics do not mean screw piles are automatically the correct foundation for every project. Ground conditions, structural loads, access and the engineering design still determine whether they are suitable.
What Ground Conditions Are Suitable for Screw Piles?
Screw piles can work in a range of ground conditions, but the correct pile cannot be selected without considering what is below the surface.
Soil conditions influence how the pile penetrates the ground, the torque achieved during installation and the depth required.
Obstructions such as large rocks, buried material or other unexpected ground conditions can also affect installation.
A soil investigation can therefore provide valuable information before the foundation is finalised.
ABC Anchors also recommends considering a test pile because it provides direct information about installation and performance at the site.
A test pile does not prove that the ground will be identical everywhere. Ground conditions can change across relatively short distances, so the foundation design and installation still need to respond to conditions encountered on site.
How Do You Choose the Right Screw Pile Foundation?
Start with the structure and the ground, not a pile catalogue.
The usual process is to establish:
The structural loads.
The ground conditions.
The required pile performance.
The appropriate pile type, diameter and helix configuration.
The number and location of piles.
The required installation torque and depth.
The connection between the piles and structure.
The installation method and equipment.
ABC Anchors' standard range includes 60R, 76R, 76RL and 89R screw pile systems, with different dimensions and torque limits available.
That does not mean a particular pile should be selected solely according to the size of the building. The correct solution depends on the engineering requirements of the individual project.
If you already have structural calculations, pile loading information or a soil investigation report, this information can be used when discussing the required screw pile system.
Do Screw Piles Need Corrosion Protection?
Corrosion and design life need to be considered as part of specifying a steel foundation system.
ABC Anchors states that, in most conditions, its screw piles can achieve a life in excess of 100 years where the top two metres are galvanised. Additional corrosion-protection measures may be required in more aggressive environments, including salt water, wet peat and soils subject to saturation or low soil resistivity.
The required protection should therefore reflect the environment in which the piles will be installed rather than assuming that every site presents identical corrosion conditions.
Further technical information is available on our screw piles product page.
Can Screw Piles Be Removed and Reused?
Potentially, yes.
Because screw piles are installed by rotation, they can in some circumstances be removed by reversing the process.
Whether an individual pile can then be reused depends on its condition. A removed pile should be inspected before reuse to establish whether it remains structurally suitable and continues to meet the project requirements.
This characteristic can be particularly relevant when designing foundations for certain temporary structures.
Screw Pile Installation and Training
Correct installation matters just as much as selecting the correct pile.
Installers need to understand the equipment, pile specification, required torque, installation depth, extensions, terminations and the procedure to follow when site conditions differ from what was expected.
ABC Anchors provides installation equipment including handheld and machine-mounted torque heads for different pile sizes and access requirements.
Training is also available for contractors and installers who need to understand how to install screw pile systems correctly and safely.
See our screw pile installation equipment and screw pile training information for further details.
Helical Piles, Screw Piles or Ground Screws: Start With the Project Requirements
Whether you searched for helical screw piles, helical piles, a helical pile foundation, screw pile foundations, ground screws or screw piles, the name is only the starting point.
For structural foundation work, what matters is selecting a pile system that suits the loads, ground conditions, installation requirements and connection to the structure.
ABC Anchors designs and manufactures screw pile systems in the UK, with pile ranges, installation equipment, terminations and technical support available for projects with different structural and site requirements.
If you are planning a project and need help identifying the appropriate screw pile system, contact ABC Anchors with your structural calculations, pile loading information or soil investigation details to discuss your requirements.
Frequently Asked Questions
1. Are screw piles and helical piles the same thing?
Yes, in foundation construction, screw piles and helical piles generally describe the same type of foundation system. "Screw pile" refers to the rotational installation method, while "helical pile" refers to the helical plates or flights attached to the steel shaft. You may also see the combined term "helical screw piles".
2. What is a helical screw pile?
A helical screw pile is a steel foundation element with one or more helical plates attached to its shaft. The pile is rotated into the ground using torque until the required installation conditions are achieved. It can then be connected to the structure above using an appropriate termination.
3. What is a screw pile foundation?
A screw pile foundation uses screw piles to transfer structural loads into suitable ground. The piles are installed at positions determined by the foundation design and connected to the structure above. The number, size, depth and arrangement of piles depend on factors including structural loads and ground conditions.
4. What is the difference between screw piles and ground screws?
The terminology can overlap because both describe steel foundation elements installed into the ground by rotation. "Ground screw" is frequently used for systems associated with lighter structures and applications such as solar panels, whereas "screw pile" or "helical pile" is commonly used for engineered structural foundations. The product specification and load requirements are more important than the name alone.
5. How do helical piles work?
Helical piles transfer structural loads from a building or structure into the surrounding ground. During installation, the pile is rotated into the soil and installation torque is monitored. The relationship between installation torque and pile capacity can then form part of assessing whether the pile has achieved the required performance.
6. How are screw piles installed?
Screw piles are installed by applying rotational torque using suitable installation equipment. Depending on the pile and site conditions, this can include handheld or machine-mounted torque equipment. Torque is monitored as the pile advances, and extensions can be added where required to continue the pile to the necessary depth and ground resistance.
7. How much weight can a screw pile support?
There is no single load capacity for every screw pile. Capacity depends on the pile specification, helix configuration, installation torque, ground conditions, pile depth and whether the pile is resisting compression or tension. The project's structural engineer should establish the required design loads and Safe Working Load.
8. Can screw piles be used for house foundations?
Screw piles can be used for new build foundations and extensions where they are appropriate for the structural loads and ground conditions. The foundation should be designed for the individual project rather than selecting piles solely according to the size or type of building.
9. What ground conditions are suitable for screw piles?
Screw piles can be installed in a range of ground conditions, but soil type, density, obstructions and changes in ground strata can affect pile selection, installation depth and achievable torque. A soil investigation or test pile can provide useful information when determining an appropriate foundation solution.
10. Do screw piles need concrete?
The screw pile itself is mechanically rotated into the ground and does not require a concrete foundation around the pile during normal installation. The complete foundation design may still incorporate concrete or other structural components depending on how the piles are connected to and used within the structure.
11. Can screw piles take loads immediately after installation?
Yes. Correctly specified and installed screw piles can accept their specified loads immediately after installation because there is no requirement to wait for concrete surrounding the pile to cure. The pile must still achieve the installation and engineering requirements specified for the project.
12. Can helical piles resist both compression and uplift?
Helical pile systems can be designed for compression and tension loads where appropriately specified. Compression pushes the foundation downwards, while tension or uplift attempts to pull it upwards. The pile design, helices, ground conditions and required loads all need to be considered when specifying the system.
13. How deep do screw piles need to go?
There is no single installation depth suitable for every screw pile foundation. Required depth depends on the ground conditions, pile specification, structural loads and installation torque. Piles may require extensions where suitable ground resistance has not been achieved at the initial depth.
14. Are screw piles suitable for restricted-access sites?
They can be. Different screw pile sizes can be installed using different equipment, including handheld torque heads for appropriate piles. This can make screw piles useful for some extensions, existing properties and other sites where access for larger foundation equipment is restricted.
15. Can screw piles be removed?
Screw piles can potentially be removed by reversing the rotational installation process. This can make them relevant to certain temporary structures. Whether a removed pile can subsequently be reused depends on its condition and whether it remains suitable for the requirements of the new project.
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