What are bottom driven steel cased piles and when can they be used?
Bottom driven steel cased piles provide a compact piling solution for residential, commercial and restricted-access projects.
The system uses steel casing driven into the ground by an internal drop weight or a percussive hammer known as a Grundomat. Once the required depth or driving resistance has been achieved, the casing is filled with concrete and reinforced to form the completed pile.
Dawson Foundation Engineering routinely designs and installs bottom driven steel cased piles for projects throughout the UK, including house extensions, new developments and schemes where access for larger piling equipment is limited.
Further technical information is available on our Bottom Driven Steel Cased Piles service page.
What Are Bottom Driven Steel Cased Piles?
A bottom driven steel cased pile consists of a steel tube that is driven into the ground from within the casing.
The pile begins with a closed-ended length of steel tube known as the starter section. The base of this section is sealed with a welded plate, and limestone is placed inside the casing to form a driving pack.
An internal drop weight or Grundomat hammer repeatedly strikes the driving pack, transferring energy through the closed end of the casing and advancing the pile into the ground.
Once the starter section has been driven to slightly above ground level, an open-ended length of steel casing, known as a follower section, is welded to it.
The driving process is then repeated, with additional follower sections added until the pile reaches either:
- The specified design length
- The required rate of penetration
- The resistance required by the pile design
The completed casing is then filled with concrete and reinforcement.
How Are Bottom Driven Piles Installed?
The installation process generally follows these stages:
- The pile position is set out in accordance with the foundation design.
- A closed-ended starter casing is placed at the pile location.
- Limestone is added inside the starter casing to create the driving pack.
- An internal drop weight or Grundomat hammer drives the casing into the ground.
- Once the starter section approaches ground level, a follower casing is welded onto it.
- The driving process continues, with further follower sections added where required.
- Installation stops when the specified design length or required driving resistance has been achieved.
- The casing is filled with concrete.
- Reinforcement is installed in accordance with the pile design.
- The completed pile is connected to the ground beam, pile cap or wider foundation system.
The exact installation sequence and pile specification will depend on the ground conditions, structural loading and practical constraints of the site.
What Is a Grundomat Pile?
A Grundomat is a compact percussive hammer that can be used to drive steel pile casings into the ground.
The equipment operates inside the steel tube and repeatedly strikes the driving material at the base of the casing.
Its compact size makes the system particularly useful for residential and restricted-access projects where larger piling machinery cannot reach the proposed foundation area.
Read more in our guide: Grundomat Piles Explained.
Advantages of Bottom Driven Steel Cased Piles
| Advantage | Why It Matters |
|---|---|
| Compact equipment | The method can be installed without a large piling rig, making it suitable for restricted-access and residential sites. |
| Cost-effective installation | Bottom driven piles can provide an economical piled solution for house extensions and smaller structures where the method is suitable. |
| No spoil from boring | The casing is displaced into the ground rather than excavated, so no spoil is created during pile installation. |
| Lower vibration than some driven systems | The compact internal driving method can produce less vibration than other driven piling techniques. |
| Permanent steel casing | The steel casing remains in the ground and contains the concrete forming the completed pile. |
| Useful on confined sites | The system can be used where narrow access routes, existing buildings or limited working space prevent larger equipment from operating. |
What Pile Diameters Are Available?
Dawson Foundation Engineering routinely installs bottom driven steel cased piles in the following diameters:
- 100mm
- 150mm
- 168mm
- 220mm
- 273mm
- 323mm
The correct pile diameter will depend on:
- The structural loads being supported
- The ground conditions
- The required pile depth
- The reinforcement specification
- The available access and installation equipment
- The proposed ground beam or pile-cap arrangement
A pile diameter should not be selected based on cost or access alone. It must be capable of satisfying the structural and geotechnical requirements of the project.
When Are Bottom Driven Steel Cased Piles Used?
Bottom driven piles may be considered for:
- House extensions
- New-build homes
- Small residential developments
- Internal piling works
- Restricted-access projects
- Projects where spoil removal would be difficult
- Ground-beam foundation systems
- Commercial structures where the required loads and ground conditions suit the method
The system is particularly useful where compact equipment is required and a driven pile can reach the necessary depth and resistance.
Bottom Driven Piles for House Extensions
House extensions are one of the most common applications for bottom driven steel cased piles.
Rear and side extensions can have restricted access, limited working space and ground conditions that prevent conventional strip foundations from providing a suitable solution.
Compact bottom driven piling equipment can often be transported through narrow access routes and operated within confined residential sites.
Once the piles have been installed, they are commonly connected using reinforced concrete ground beams that support the proposed extension.
View a relevant project: Bottom Driven Piling Works for a Residential Extension in Camden.
You can also view our Residential Piling services.
Bottom Driven Piles and Ground Beams
Bottom driven steel cased piles are often installed as part of a wider piled foundation system incorporating reinforced concrete ground beams.
The ground beams connect the individual piles and transfer loads from the proposed building into the pile foundations.
Depending on the design, associated works may include:
- Excavation for ground beams
- Breaking down or preparing pile heads
- Reinforcement installation
- Formwork
- Concrete placement
- Floor slabs or pile caps
- Excavation and spoil removal
Dawson Foundation Engineering can undertake both the piling and associated reinforced concrete foundation works.
View an example: Bottom Driven Piling and Ground Beams for a Residential Project.
Are Bottom Driven Piles Suitable for Restricted Access?
Bottom driven piling is frequently selected where access for larger piling rigs is not available.
Typical access constraints may include:
- Narrow routes between buildings
- Rear garden extensions
- Low doorways
- Internal working areas
- Existing occupied properties
- Limited space for rig manoeuvring
Although the installation equipment is compact, the site must still provide sufficient space to transport and store casing sections, operate the driving equipment, complete welding and place concrete and reinforcement.
Read more about restricted access piling.
How Do Ground Conditions Affect Installation?
The ground conditions influence the required pile depth, driving resistance and suitability of the method.
A site investigation can help identify:
- Soil type, strength and consistency
- The depth of suitable bearing material
- Weak or compressible layers
- Made ground and variable fill
- Groundwater conditions
- Buried concrete, boulders or other obstructions
Bottom driven piles displace the ground as the casing advances. Significant buried obstructions may prevent the pile from reaching the required depth or driving resistance.
Where the ground contains dense obstructions or rock, an alternative method such as overburden drill and case piling may be more appropriate.
Read more about why site investigation is important for pile design.
Can Bottom Driven Piles Be Used in Made Ground?
Bottom driven steel cased piles may be considered where unsuitable made ground must be bypassed so loads can be transferred into stronger material below.
The method produces no spoil during pile installation, which can be useful where excavation and disposal would be difficult or expensive.
However, made ground can contain old foundations, concrete, masonry, cobbles or other obstructions that affect the driving process.
The suitability of the method will therefore depend on the composition and depth of the fill and the conditions beneath it.
Read our guide to piling in made ground.
Do Bottom Driven Piles Create Spoil?
Bottom driven piles do not create bored spoil because the steel casing is driven into the ground rather than installed within a pre-excavated hole.
This can provide several practical benefits:
- Reduced material requiring removal from site
- Less disruption within confined working areas
- Reduced spoil-handling requirements
- A cleaner installation process on residential sites
- Potential benefits where contaminated or difficult material would otherwise require disposal
Excavation may still be required for ground beams, pile caps, floor slabs and associated foundation works.
Noise and Vibration Considerations
Bottom driven steel cased piles are installed using a percussive driving method.
The internal drop weight or Grundomat repeatedly strikes the driving pack at the base of the casing, so noise and vibration must be considered when planning the work.
The method can create lower vibration than some other driven piling systems, but suitability will depend on:
- The proximity of neighbouring buildings
- Sensitive structures or infrastructure
- Occupied properties
- Site-specific noise restrictions
- The ground conditions
- The pile diameter and installation equipment
Where noise or vibration restrictions prevent driven piling, a bored method such as Sectional Flight Auger piling may be considered.
Bottom Driven Piles vs Other Mini-Piling Methods
Bottom driven steel cased piling is one of several methods that may fall within the wider category of mini piling.
| Method | Installation Principle | Typical Consideration |
|---|---|---|
| Bottom driven steel cased piles | Steel casing is driven using an internal weight or hammer and then filled with concrete. | Compact equipment and no bored spoil. |
| Sectional Flight Auger piles | Short auger sections bore into the ground before the pile is concreted and reinforced. | Low vibration and suitable for restricted headroom. |
| Screw piles | Steel shafts with helical plates are mechanically rotated into the ground. | Minimal excavation and immediate connection to some structures. |
| Overburden drill and case piles | Steel casing is drilled through difficult overburden and obstructions. | Useful where driven or augered methods may encounter refusal. |
The correct method must be selected using the ground conditions, structural loads, access, noise and vibration constraints and required foundation arrangement.
Learn more in our guide to the different types of mini piling.
Working Area and Site Preparation
Compact equipment reduces the space required for installation, but a safe and suitable working area must still be provided.
The site must accommodate:
- The piling equipment
- Steel casing sections
- Welding activities
- Concrete and reinforcement
- Safe access for personnel
- Ground-beam excavation where required
The ground must be capable of supporting the selected equipment throughout the installation works.
Depending on the site and plant used, an existing hardstanding, prepared working area or engineered platform may be required.
Read more about working platforms for piling equipment.
Project Examples
Dawson Foundation Engineering has completed bottom driven piling and ground-beam works on residential projects throughout the UK.
Relevant examples include:
- Bottom Driven Piling for a Residential Extension in Camden
- Rapid Bottom Driven Piling and Ground Beams for a Residential Project
- Domestic Piling and Ground-Beam Works in Swadlincote and Whickham
These projects demonstrate how compact bottom driven piling equipment can be combined with reinforced concrete ground beams to deliver complete residential foundation packages.
Are Bottom Driven Steel Cased Piles Suitable for Your Project?
Bottom driven steel cased piles can provide a compact, efficient and low-spoil foundation solution for residential, commercial and restricted-access projects.
However, the method must be selected according to the ground conditions, structural requirements, access, noise and vibration constraints and the risk of buried obstructions.
Dawson Foundation Engineering routinely installs 100mm, 150mm, 168mm, 220mm, 273mm and 323mm diameter bottom driven piles.
To discuss your project, call 0333 224 5196 or contact our team to arrange a free site visit and no-obligation quotation.
