How Deep Should a Bollard Be Installed? | Aremco Barriers
How Deep Should a Bollard Be Installed?
How deep does a bollard need to go into the ground?
Unfortunately, there isn't one installation depth that is correct for every bollard.
The required depth depends on the design of the bollard, its overall dimensions, the manufacturer's specification, ground conditions and what the bollard is intended to do.
A small parking bollard and a substantial steel protection bollard shouldn't automatically be installed using the same foundation.
At Aremco Barriers, we manufacture and supply a range of steel bollards for commercial, industrial and private applications throughout the UK. In this guide, we explain the main factors that determine how deep a bollard should be installed and why the foundation is just as important as the bollard itself.
What Is a Root-Fixed Bollard?
A root-fixed bollard has a section of the post designed to extend below ground level.
A foundation hole is excavated, the bollard is positioned at the correct height and alignment, and concrete is placed around the below-ground section to secure it.
You may also hear this type of installation described as:
- Built in
- In-ground
- Concrete in
- Root mounted
The section below ground is often referred to as the root.
How Deep Should the Bollard Go Into the Ground?
The first thing to check is the specification for the particular bollard being installed.
Different products are manufactured with different root lengths.
For example, one Aremco fixed steel bollard may have an overall height of 1030mm, with approximately 300mm intended to be installed below ground, leaving approximately 730mm above ground.
However, this does not mean that every bollard should have a 300mm root.
Other products can have significantly different dimensions and installation requirements.
Always work from the specification for the actual bollard being installed rather than using a general rule taken from another product.
Is the Root Depth the Same as the Foundation Depth?
Not necessarily.
This is an important distinction.
If a bollard has a 300mm root, it doesn't automatically mean you should simply dig a 300mm-deep hole and fill it with concrete.
The foundation may need to extend beneath the bottom of the bollard, depending on the installation design, drainage requirements and ground conditions.
The bollard root depth and the overall excavation or foundation depth are therefore not necessarily the same measurement.
How Wide Should the Foundation Be?
Again, there isn't one foundation size suitable for every bollard.
The required foundation dimensions can depend on:
- Bollard size
- Bollard height
- Steel section
- Intended use
- Ground conditions
- Surface type
- Expected loads
- Manufacturer's installation requirements
A substantial bollard installed in poor ground may require a different foundation from a smaller bollard installed in firm, stable ground.
Why Is the Concrete Foundation Important?
The bollard and foundation work together.
Even a substantial steel post will not perform as intended if it is installed into an inadequate foundation.
The concrete helps transfer forces from the bollard into the surrounding ground and keeps the post correctly positioned.
An inadequate installation could potentially allow the bollard to:
- Lean
- Become loose
- Move in the ground
- Rotate
- Drop out of alignment
This is why the installation shouldn't be treated as an afterthought.
Does the Type of Ground Matter?
Yes.
Ground conditions can have a major influence on the foundation required.
Examples include:
- Firm natural ground
- Clay
- Loose soil
- Made-up ground
- Soft ground
- Waterlogged ground
- Existing concrete
- Areas containing rubble or fill
If the ground is poor or unusual, additional advice may be required before deciding on the foundation dimensions.
Don't assume that a foundation suitable for one site will automatically be suitable somewhere else.
Can I Install a Bollard Through Tarmac?
A root-fixed bollard can potentially be installed in a tarmac area, but the tarmac itself isn't the foundation.
The surface would normally need to be cut and excavated so that an appropriate concrete foundation can be formed beneath it.
Once the bollard has been installed, the surrounding surface can be made good as required.
Can I Install a Bollard Through Block Paving?
Again, the paving blocks themselves shouldn't be treated as the structural foundation.
Blocks may need to be removed so that the ground beneath can be excavated and the appropriate foundation constructed.
The paving can then be reinstated around the bollard after installation.
What About Installing Into Existing Concrete?
If suitable structural concrete already exists, a bolt-down bollard may sometimes be an alternative to a root-fixed product.
A bolt-down bollard normally has a base plate that sits on the surface and is secured using suitable anchors.
However, the existing concrete needs to be suitable.
Its thickness, condition, reinforcement, edge distances and the loads imposed by the bollard should all be considered.
The fact that a surface looks like concrete doesn't automatically mean it is suitable for a bolt-down installation.
How Deep Does a Removable Bollard Need to Be?
Removable bollards work differently from conventional fixed bollards.
Instead of the post being permanently concreted into the ground, a ground socket is installed below the surface.
The bollard is inserted into the socket when vehicle restriction is required and removed when access is needed.
The excavation therefore needs to accommodate the socket as well as any foundation and drainage requirements.
Always use the dimensions and installation information for the particular removable bollard being installed.
How Deep Does a Telescopic Bollard Need to Be?
Telescopic bollards generally require considerably more below-ground space because the inner post lowers into an underground outer casing.
For example, an Aremco telescopic security bollard is approximately 600mm above ground when raised and approximately 785mm deep when lowered into its below-ground housing.
The installation therefore needs sufficient excavation depth to accommodate the complete casing together with the required foundation and drainage arrangement.
This is one reason why checking for underground services is particularly important before installing telescopic bollards.
Drainage Is Important
Below-ground bollards and sockets can be exposed to rainwater.
If water has nowhere to escape, it can collect within or around the installation.
This is particularly important for:
- Telescopic bollards
- Removable bollard sockets
- Other below-ground mechanisms
The installation should therefore follow the drainage recommendations for the particular product and take local ground conditions into account.
Poorly draining ground may require additional consideration.
Check for Underground Services Before Digging
Before excavating any bollard foundation, the area should be checked for underground services.
These can include:
- Electricity cables
- Gas pipes
- Water mains
- Drainage
- Telecommunications
- Fibre-optic cables
- Other buried services
This is especially important for deep installations such as telescopic bollards.
Never assume an area is clear simply because there are no visible signs of services above ground.
How Much of the Bollard Should Be Above Ground?
This depends entirely on the design of the bollard.
The manufacturer will normally specify the intended above-ground height.
You shouldn't simply decide to bury more or less of the bollard to achieve a different finished height.
Changing the installation depth could alter how the product performs and may also affect features such as:
- Reflective bands
- Handles
- Locking mechanisms
- Crossbars
- Ground sockets
- Telescopic mechanisms
If you require a particular finished height, discuss this before ordering.
Should the Bollard Be Installed Completely Vertical?
Yes, unless the particular product is specifically designed otherwise.
The bollard should be checked for level and alignment during installation.
This is particularly important while concrete is being placed and before it has cured.
A bollard that is allowed to move during installation could end up permanently leaning.
Where several bollards are installed in a row, checking their height, spacing and alignment can also make a considerable difference to the finished appearance.
How Far Apart Should Bollards Be Installed?
Depth isn't the only measurement to consider.
The spacing between bollards depends on the purpose of the installation.
If the intention is to discourage normal vehicles from passing between them, the gap needs to be selected accordingly.
You should also consider:
- Pedestrian movement
- Wheelchair access
- Mobility equipment
- Site layout
- Vehicle dimensions
- Emergency access requirements
There isn't one spacing that should automatically be applied to every site.
Does a Deeper Foundation Make a Bollard Stronger?
Not automatically.
Simply digging an unnecessarily deep hole isn't a substitute for a properly designed installation.
Foundation performance depends on several factors, including its width, depth, concrete, surrounding ground and the way loads are transferred.
The correct approach is to install the product according to its specification and the site conditions rather than assuming that "more concrete" will solve every problem.
What If the Bollard Is Intended to Protect a Building?
If bollards are being installed around a building, doorway, loading area or piece of equipment, first establish what level of protection is actually required.
Standard steel bollards can provide a useful physical and visual vehicle restriction, but they shouldn't automatically be regarded as crash-rated bollards.
If a project requires a particular vehicle impact rating or hostile vehicle mitigation performance, a product specifically tested and certified to the required standard should be specified.
Common Bollard Installation Mistakes
Some of the problems worth avoiding include:
- Using a generic foundation size for every bollard
- Not checking the manufacturer's installation requirements
- Treating tarmac as a structural foundation
- Failing to check for underground services
- Installing the bollard at the wrong height
- Poor alignment
- Insufficient drainage
- Using unsuitable concrete or fixings
- Installing before considering vehicle and pedestrian routes
Taking a little more time to plan the installation can prevent much bigger problems later.
How Deep Should My Bollard Be? – Quick Answer
There is no universal bollard installation depth.
The correct depth depends on the bollard you are installing.
Always establish:
1. The specified below-ground/root dimension of the bollard
2. The required foundation dimensions
3. The local ground conditions
4. Whether drainage is required
5. The location of underground services
6. The intended finished height above ground
These should all be considered before excavation begins.
Need Help With Bollard Installation Requirements?
If you're buying a bollard from Aremco Barriers and aren't sure about the installation requirements, speak to us before preparing the foundations.
Tell us which bollard you are considering and provide information about the proposed installation area.
Photographs of the site can also be extremely useful.
Aremco Barriers manufactures and supplies fixed, removable, telescopic and fold-down steel bollards alongside a wider range of manual vehicle access-control products for commercial, industrial and private applications throughout the UK.
Please note: Foundation requirements can vary according to the product and site conditions. Installation information should be considered alongside the conditions at the individual site.
Frequently Asked Questions
How deep should a fixed bollard be concreted into the ground?
It depends on the design of the bollard. Always use the specified root depth and installation requirements for the particular product rather than assuming there is a standard depth for all bollards.
Is 300mm deep enough for a bollard?
Some bollards are designed with a 300mm below-ground root, but this doesn't mean 300mm is suitable for every bollard or that the complete foundation should only be 300mm deep.
Do bollards need concrete foundations?
Root-fixed steel bollards are normally installed into suitable foundations. The required foundation will depend on the product and site conditions.
Can I concrete a bollard directly into tarmac?
Tarmac itself isn't a suitable concrete foundation. The area normally needs to be excavated so an appropriate foundation can be constructed below the surface.
Do telescopic bollards need drainage?
Drainage is an important consideration for below-ground telescopic bollard housings. Installation should follow the requirements for the particular product and take the site's drainage conditions into account.
Should I check for underground services before installing a bollard?
Yes. Underground services should be identified before excavation or drilling begins.
Does Aremco provide installation information?
Installation requirements vary by product. If you're purchasing an Aremco bollard and are unsure about the installation, contact us before preparing the foundations.
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