There is a growing trend within the highways and civil engineering sectors towards using thicker layers of flowable mortar and similar materials when installing or reinstating ironwork. The logic is understandable — if an installation has failed, more material should provide greater strength and support.

But is more mortar really the answer?

SHIMPAC® believes the industry should consider whether increasing the quantity of a material that can still be susceptible to cracking, shrinkage or deterioration genuinely addresses the cause of failure.

This is not an argument against flowable mortars. Mortar has played an important role in construction and highways for decades. The question is whether increasing reliance on mortar-based solutions can deliver the long-term performance required by modern roads.

The changing demands on the network

Today's roads face heavier traffic and greater demands than ever before. Since 2022, certain HGVs have been permitted to operate at weights of up to 48 tonnes, increasing the pressure placed on infrastructure.

Ironwork seating systems must withstand the forces generated by vehicles passing over access covers, manholes and gully gratings. They must also cope with rainfall, temperature fluctuations and repeated freeze-thaw cycles. Water ingress, movement and poor installation can all contribute to failure.

Against this backdrop, simply filling the void with more material and allowing it to harden may not be enough.

The problem with more of the same

When an installation fails because its supporting material has cracked, deteriorated or lost integrity, increasing the thickness of that same material may not solve the underlying issue.

Mortar-based installations can deteriorate through shrinkage, cracking, water ingress, movement, temperature changes and increasing traffic stresses. Over time, a material intended to provide support can become the installation's weakest point.

Movement can create gaps between ironwork and the surrounding carriageway, allowing water beneath the road surface. Freeze-thaw action can accelerate deterioration, while repeated traffic loading continues to apply shear and compression forces.

The result is often a cycle of repairs, road closures, traffic management and additional costs. Unless the root cause is addressed, repeated intervention can become inevitable.

(Image: SHIMPAC®)

A different approach

SHIMPAC® takes a different approach. Rather than relying on increasing quantities of mortar as the primary seating and levelling solution, it is a fully engineered system designed to provide precise, durable support for ironwork installations.

The system uses ROADSHIMS® to achieve millimetre precision, enabling ironwork to be accurately positioned and aligned with the surrounding road surface. Correct alignment helps distribute traffic forces more effectively and reduces unnecessary movement within the installation.

Designed to withstand the shear and compression forces generated by modern traffic, SHIMPAC® helps maintain installation integrity throughout the asset's service life.

Less material, better engineering

Sustainable infrastructure is not simply about using more materials. It is about selecting the right materials, reducing waste and delivering solutions that last longer.

Every failed installation has environmental and economic consequences. Materials must be replaced, traffic management installed and operatives returned to site.

SHIMPAC® is designed to help break this cycle. When correctly installed, the system has demonstrated exceptional longevity, with its earliest installations now more than 35 years old and no reported failures.

True sustainability should consider not only the materials used initially, but also the lifespan of the finished installation.

A long-term solution

Increasing traffic loads, heavier vehicles, unpredictable weather and pressure on local authority budgets demand a more considered approach to highway maintenance.

SHIMPAC® does not suggest that mortar has no place in highway construction. Instead, it challenges the assumption that ironwork failures can always be resolved by using more of it.

Sometimes the answer is not more material. It is better engineering.