Height, diameter and foundation depth
Bollard size is one of the most important factors in how well a bollard performs in service. Height, diameter and foundation depth together determine how much impact energy the bollard can absorb, how visible it is to drivers and pedestrians, and how well it suits its environment. Bollard Supplies manufacture a standardised but flexible range of bolt-down and dig-in bollards in Leicester, offering a consistent palette of diameters and heights that can be tuned to different applications, with bespoke sizes available where a project demands something outside the standard envelope.
Across both bolt-down and dig-in designs, the core dimensional range is deliberately aligned. For both versions, Bollard Supplies offer bollard diameters of 114 mm, 139 mm, 168 mm, 193 mm and 219 mm. This means that whether a scheme is based on surface-mounted (bolt-down) or foundation-mounted (dig-in) posts, visual consistency can be maintained while the foundation detail is varied to suit ground conditions and loading. The primary distinction is therefore not the diameter, but the overall length and the way that length is split between above-ground height and below-ground embedment
Bollard Height
Bollard height is the second critical dimension, and here the standard ranges for bolt-down and dig-in diverge. The bolt-down bollard is offered in overall heights of 1.0 m, 1.2 m, 1.5 m and 1.8 m. Because bolt-down units are mounted on a base plate directly to a concrete slab, these figures correspond closely to the visible height above the finished surface.
The dig-in bollard, by contrast, is offered in overall lengths of 1.5 m, 1.8 m, 2.0 m and 2.5 m. A portion of this length is intended to be buried in concrete, leaving a similar visible height above ground typically in the 0.8–1.2 m range depending on design and risk level but with a much deeper foundation and higher bending capacity at ground level.
Standard Bollard Height
These standard height options reflect typical UK practice for bollard and post design.
Bollard Supplies suggest that bollards in the region of 800–1,000 mm above ground are appropriate for car parks, providing good visibility to drivers while remaining at a manageable scale. For pedestrian guidance, heights of roughly 900–1,000 mm above ground are common, while for more robust vehicle-exclusion duties, heights up to about 1,200 mm are used, especially when combined with deeper foundations and heavier sections.
Dig-in variants are recommended where maximum strength is required, which is why the longest 2.0 m and 2.5 m options are only provided in dig-in format rather than bolt-down
Bollard Diameter
Diameter is a strong indicator of the duty level. The 114 mm bollard is relatively slim and well suited to low to medium-risk environments such as staff car parks, light traffic areas and general pedestrian demarcation. At this size, the bollard is visually clear but not overbearing, and the section is sufficient to withstand knocks from cars manoeuvring at low speed, particularly for bolt-down units fixed to sound concrete. Stepping up to 139 mm and 168 mm increases the section modulus and therefore impact resistance. These intermediate diameters are often chosen for mixed-use environments such as retail parks, warehouse yards and distribution centres where vans, cars and occasional HGVs share space. The largest diameters, 193 mm and 219 mm, provide significantly higher bending resistance and are more appropriate where repeated HGV impacts or protection of expensive assets, structural columns or vulnerable building façades are anticipated. The fact that all these diameters are available in both bolt-down and dig-in formats allows designers to match visual appearance while tailoring structural performance via the foundation detail.
Bollard Materials
Material and finish interact with size as well. Bollard Supplies manufacture their bollards from heavy-duty steel, with galvanised and galvanised plus yellow powder-coated options as standard. Galvanising is carried out to the relevant British standards for corrosion protection, and the powder-coated yellow finish enhances visibility in car parks, warehouse interiors and loading yards. Reflective or high-contrast stripe bands may be added in one to eight bands for additional conspicuity. These finishing options mean a 114 mm bollard can still be highly visible despite its smaller diameter, while a larger 193 or 219 mm unit can be blended into the architecture using alternative RAL colours where aesthetics are important.
Bolt Down Bollards
In bolt-down form, the bollard is essentially a cantilevered steel tube or hollow section welded to a base plate. The base plate is drilled to accept mechanical or chemical anchors, and Bollard Supplies offer a choice of supplying four ground anchors with the unit. A typical installation will involve drilling the existing slab, installing four M16-class anchors and torquing to specification. Because the entire bollard sits above the slab, the nominal height of 1.0–1.8 m is essentially the working height. The limiting factors for a bolt-down unit are the thickness and quality of the concrete slab, the base-plate geometry, and the anchor configuration. On a good quality industrial floor, a 168 mm or 193 mm bolt-down bollard at 1.2 or 1.5 m high will provide substantial impact resistance for standard car park and warehouse traffic, while still being relatively simple to install and, if necessary, remove or replace.
Dig In Bollards
Dig-in bollards remove the dependence on an existing slab and instead rely on a cast-in foundation. Here the extra length of 1.5–2.5 m becomes important. A typical dig-in detail might require 500–900 mm of embedment below ground level, depending on the bollard diameter, expected impact loads and soil conditions. A 2.0 m or 2.5 m dig-in bollard allows enough length to provide 0.9–1.2 m visible height while still achieving a deep concrete footing that resists bending and pull-out. Because the bollard is concreted in, the system behaves as a fixed-ended cantilever rather than a simple base-plate connection, which increases stiffness at ground level and makes dig-in bollards better suited to high-risk locations such as road edges, site entrances or industrial verges where vehicle speeds and masses may be greater.
Bollard Height Ranges
Comparing the height ranges for the two formats shows the design intent clearly. The shortest 1.0 m option is only offered as a bolt-down unit, aimed at low-risk areas with good slab construction and modest impact requirements. The 1.2 and 1.5 m options are offered for bolt-down with the assumption that the full length is visible, making them ideal where extra visual presence or higher protection height is needed, for example near loading bays, fuel pumps or building corners. The dig-in range starts at 1.5 m because anything shorter would not leave an adequate embedment depth once the desired above-ground height is achieved; by starting at 1.5 m, installers have enough length to bury a significant portion in concrete while still satisfying visibility requirements. The 2.0 and 2.5 m dig-in options are arranged specifically to give designers the freedom to increase either embedment depth, above-ground height, or both, depending on risk assessment.
Bollard Diameters
In terms of diameters, bolt-down and dig-in share the same palette, but their performance is realised differently. A 139 mm dig-in bollard with 700–800 mm embedment will typically outperform a 139 mm bolt-down bollard on a thin slab, particularly for impacts near ground level, because the substrate and foundation mass are doing more of the work. Conversely, if the slab is thick and well reinforced, a 193 mm bolt-down bollard at 1.2 m high can provide excellent impact performance while also offering the practical benefits of quicker installation, reduced excavation and straightforward replacement. This is why Bollard Supplies promote bolt-down units for locations with existing concrete foundations, and dig-in units for locations without a prepared surface or where additional strength is required.
Bollard Applications
Typical applications on the site illustrate how these size options are used in practice. For standard car parks and pedestrian demarcation, a 114 or 139 mm diameter bollard at around 1.0–1.2 m visible height is usually sufficient. In a multi-storey or surface car park with a good concrete deck, bolt-down units are attractive because they avoid breaking out and reinstating slabs; a 1.0 or 1.2 m bolt-down bollard in 114 or 139 mm diameter provides clear visual guidance and moderate collision protection. In open-air car parks on tarmac over weaker sub-bases, dig-in bollards may be preferred so that the bollard load is transferred into a dedicated concrete footing rather than into the surfacing.
Industrial Bollards
Industrial estates, warehouse yards and loading bays often justify larger diameters and heights. Here, 168 mm, 193 mm or even 219 mm sections become more appropriate because the masses and operating speeds of vehicles increase. A 1.2 or 1.5 m bolt-down bollard in 168 or 193 mm diameter, fixed into a thick warehouse slab, works well to protect roller shutter openings, racking ends and mezzanine supports. Wherever there is concern about slab quality, or where bollards sit just off the slab on hardcore or soil, the same diameters in dig-in format with overall lengths of 1.8–2.5 m allow deeper concrete foundations to be poured, greatly increasing resilience to impact and reducing the risk of progressive damage to the pavement structure around the base.
Roadside Bollards
Roadside and perimeter protection schemes tend to push designs toward the top of the dig-in range. Where bollards are used to prevent vehicle ingress onto footpaths, cycleways or building frontages from public highways, the risk profile reflects the possibility of heavier vehicles at higher speeds. In this context, 193 mm or 219 mm dig-in bollards with 2.0–2.5 m overall length and substantial concrete footings are more appropriate. Even though the visible height remains in the familiar 0.9–1.2 m band for good ergonomics and sight lines, the extra below-ground length is what delivers the necessary structural capacity.
Bollard Spacing
There is also a relationship between bollard spacing and size. While the Bollard Supplies website focuses on individual bollard dimensions, standard practice is to space posts so that clear gaps between bollards are narrower than the track width of the vehicles being excluded, typically in the 1.2–1.5 m range for car parks. When using smaller diameters, tighter spacing may be chosen to reinforce the visual and physical barrier; with 193–219 mm bollards, spacing can be slightly more generous while still maintaining a strong psychological and physical deterrent. In all cases, the designer balances diameter, height, spacing and foundation detail to meet a specific risk profile and site geometry.
A further consideration is how bollard size interacts with other elements of a site’s protection system, such as Armco beams and posts. Bollard Supplies’ wider product range includes Armco beams and posts at standard heights of 560 mm, 610 mm, 760 mm and up to 1,100 mm for double-row HGV protection. These heights provide a useful reference; for example, bollards protecting the ends of barrier runs or supporting gate posts can be selected so that their impact height aligns with the barrier rail or with a vehicle’s principal impact zone. Choosing bollard heights in the 0.8–1.2 m region ensures that the bollard works in concert with adjacent guardrails and safety barriers rather than acting in isolation.
Finally, while standard diameters and heights cover most use-cases, Bollard Supplies explicitly offer bespoke bollard sizes. This is particularly useful where architectural constraints, unusual vehicle geometries, existing services or regulatory requirements dictate a non-standard solution. A streetscape project might call for a reduced visible height to preserve heritage sight lines but a larger diameter for impact resistance; an industrial facility may need extended embedment depths to suit poor ground conditions. In each case, the starting point is the established range of 114–219 mm diameters and 1.0–2.5 m lengths, which can then be adjusted to suit project-specific requirements while maintaining the proven material, welding and galvanising standards used across the range.
Bollard Size Summary
The bollard sizes offered by Bollard Supplies are built around a coherent set of diameters and heights that are available in both bolt-down and dig-in formats. Bolt-down bollards prioritise ease of installation onto existing concrete with overall heights from 1.0 to 1.8 m, while dig-in bollards use longer overall lengths from 1.5 to 2.5 m to provide deeper concrete foundations and higher structural capacity. Diameters from 114 mm to 219 mm allow designers to scale the bollard to the risk level, from light-duty car park demarcation through to heavy-duty industrial and roadside protection. Understanding how these sizes relate to visibility, impact resistance and foundation behaviour is essential to choosing the right configuration for any given project.
