Foundation and Installation Buyers Guide

Why the Foundation Is Part of the Rating

When a product is tested to PAS 68 or IWA 14, the test facility crashes a vehicle of a specified weight and speed into the exact foundation and fixing that will be sold. The rating describes what happened to that whole system, including how far the vehicle penetrated and how much debris was thrown clear. This is why installation has to follow the tested specification precisely, right down to the concrete grade and the depth and diameter of excavation.

It also explains why "which foundation depth do I need" isn't a simple question. It depends on the individual product, the vehicle weight and speed it's rated to stop, and how the manufacturer engineered it to resist that impact.

Standard (Root Fixed) Foundations

The traditional approach to HVM is a root fixed foundation: a reinforced concrete base set deep enough into the ground to resist the overturning and shear forces of a vehicle impact through mass and depth alone.

For PAS 68 bollards, standard foundation depths typically fall in the region of 600–750mm, depending on the rating and the specific product. Higher-speed, heavier-vehicle ratings generally call for a larger and more heavily reinforced foundation. Some high-security bollard systems designed to resist a 50mph impact from a heavy vehicle can call for excavation depths of up to 2 metres.

A root fixed foundation typically involves:

• Excavating to the specified depth and diameter, with no reduction in either dimension
• Installing a rebar cage or reinforcement as detailed on the product's foundation drawing
• Casting the specified grade of concrete around the base or sleeve
• Allowing the concrete to cure fully before the product is put into service

This approach remains the default where ground conditions and buried services allow for it, and it's usually the most cost-effective option per unit where deep excavation isn't a constraint. The limiting factor is what's underneath the surface: town centres, transport hubs and older sites are often dense with utilities, drainage runs, cabling and, in some cases, archaeology, all of which can rule out a deep dig.

Shallow Mount and Ultra Shallow Mount Systems

Where a standard foundation isn't practical, shallow mount and ultra shallow mount HVM products are designed to deliver the same certified level of protection using a fraction of the excavation depth.

Rather than relying on depth to resist the impact, these systems are engineered to spread the load horizontally, using a wider footprint, additional mass, or a reinforced base plate that distributes the impact force across a larger area close to the surface. This means the product doesn't need to be buried deep to stay in place; it needs to be anchored broadly and securely at a shallow depth.

Across Townscape's range, shallow foundation depths vary depending on the product and its rated speed:

• Counter Terror Blocks and the planters built around them (Ultra Shallow Mount), a 100mm recess into existing tarmac, concrete or paved surfaces, tested to PAS 68 at 30mph and 40mph ratings.
• Ultra shallow mount bollards, such as the CT40 Ultra Shallow Mount, also engineered around a 100mm foundation depth.
• Shallow mount bollards at higher ratings, such as the CT50 shallow mount range (50mph, IWA 14-1 tested) , typically require somewhere between 200mm and 400mm, depending on the specific product and array.

How the 100mm System Works in Practice

The Counter Terror Block itself is a reinforced concrete unit engineered to arrest a 7.5-tonne vehicle at 30mph or 40mph using only a 100mm recess into the surrounding surface. Because the block's mass and shape do the work of resisting the impact, rather than depth, it avoids the need for extensive groundwork and largely sidesteps the risk of striking buried services.

This same low-foundation block is used as the structural core of several other Townscape products, which is why the 100mm figure appears across more than one product category: 

• Bollards and blocks: Used directly, forming a continuous or spaced line of protection
• Concrete and timber planters (such as the Gunwharf range): Built around the same low foundation block, with the block hidden beneath a planting bed and integrated liner
• Modular planter systems (such as the HVM Flex system): Counter Terror Blocks installed within a retaining wall, which needs to be at least 600mm high above ground to fully conceal the block while keeping the 100mm below-ground fixing

In each case, the visible product (bollard, block or planter) is doing double duty: providing the certified vehicle mitigation function while presenting as ordinary street furniture or landscaping above ground.

Choosing Between Standard and Shallow Mount

The decision generally comes down to what's beneath the surface and what performance the site needs.

Standard foundations tend to suit:

• New-build schemes or sites undergoing full groundworks anyway
• Locations with a clear, well-mapped area free of services
• Sites where the very highest ratings (50mph, heaviest vehicle classes) are required, since some of these are only available as root fixed systems

Shallow mount and ultra shallow mount systems tend to suit:

• Retrofit projects on existing paving, tarmac or hard landscaping
• Sites with utilities, drainage or cabling close to the surface
• Heritage locations where excavation is restricted or archaeologically sensitive
• Projects needing rapid installation with minimal disruption to a live public space

Site Assessment Before Any Excavation

Whichever foundation type is specified, the same groundwork checks apply before digging starts:

• Utility surveys. A CAT scan (cable avoidance tool) and, where needed, ground-penetrating radar should be used to map buried services before excavation begins, regardless of foundation depth.
• Ground conditions. Existing sub-base, drainage and soil type all affect whether a foundation will perform as tested. This is particularly relevant for shallow mount systems, which rely on the surrounding surface to help distribute load.
• Existing surface makeup. For ultra shallow mount products installed into existing tarmac, concrete or paving, the condition and depth of that surface needs to be confirmed as suitable to receive the recessed unit. Find out more in our Retrofitting HVM guide. 
• Risk assessment and standoff distance. The choice of product, rating and foundation type should follow from a site-specific risk assessment covering the credible threat, achievable vehicle speed, and the standoff distance available. For government or critical infrastructure sites, the National Protective Security Authority (NPSA, formerly CPNI) provides guidance on commissioning this kind of assessment; for commercial sites, a security risk consultant is the usual starting point.

Installation Sequence: A General Overview

While every product has its own foundation drawing and installation instructions, the broad sequence is similar across both foundation types:

1. Confirm the site risk assessment and product rating match the intended installation

2. Survey for buried services and check ground conditions

3. Mark out positions, respecting the specified spacing between units (commonly 1200mm centre-to-centre for bollards, though this varies by product)

4. Excavate to the exact depth and diameter specified, never reduced, even where ground conditions make digging harder

5. Install reinforcement as detailed on the foundation drawing

6. Cast the specified concrete grade and allow it to cure for the stated period before the installation is considered load-bearing

7. Fit the visible product (bollard, block or planter shell) and any surface reinstatement (paving, tarmac, planting)

For shallow mount and ultra shallow mount products going into existing hard surfaces, the sequence is similar but condensed: the existing surface is cut and recessed to the specified 100mm (or product-specific) depth, the unit is set and levelled, often using adjustable feet, as with the Gunwharf planter range, and the surrounding surface is reinstated around it.