Clayboard void former protects New York subway

Void protection challenge beneath a busy New York subway

Urban Foundation Engineering is a trusted name in New York’s heavy construction scene. It was preparing to build a major multi-storey development in Brooklyn, including residential condos and hotel units. The site had previously been a car park, and beneath the surface lay a critical challenge: a live subway tunnel ran directly below the site.

This raised two major concerns:

1. How to prevent the new building’s load from placing pressure on the tunnel roof
2. How to minimise vibration transfer from the subway into the future structure

The client needed a solution that was technically sound, lightweight, and sustainably manufactured – and that’s where Dufaylite came in, with its Clayboard void former providing a smart, engineered void protection system to meet the demands of the project.

This wasn’t about ground heave — it was about precision separation and protection.

Commercial Clayboard: The versatile void former with global credentials

The client found Dufaylite online and was drawn to our experience in void protection for infrastructure-sensitive sites. They were particularly reassured by our history of delivering tailored, technically robust solutions, including previous work on high-profile construction projects where vibration or structural separation was critical to success.

One example that resonated with their team was our involvement in the Queensferry Crossing in Scotland – the largest infrastructure project of its kind in a generation. In that case, our commercial Clayboard was used to help manage movement and vibration forces across complex spans and foundations, reinforcing its capability beyond traditional ground heave applications.

Read more about our work on the Queensferry Crossing

Although Clayboard is predominantly used within the UK construction sector, we are increasingly supporting international commercial construction projects that require lightweight, sustainable solutions in challenging environments. In addition to this New York subway application, Clayboard has been used to protect a power station in Sudan and a multi-storey car park built over a tunnel in Gibraltar – proof of its versatility in both civil engineering and commercial build contexts.

From the first conversation, we worked closely with Urban Foundation Engineering and their partners to understand the precise demands of the Brooklyn site. Communication was key during design reviews, shared screen sessions, and ongoing technical dialogue, helping ensure the right product fit was delivered with confidence.

Clayboard for infrastructure separation and vibration reduction

After a detailed review of the site conditions, we recommended our heaviest grade of commercial Clayboard due to the depth of the slab pour and the need for controlled deflection, rather than collapse under soil heave.

Although the site itself didn’t require ground heave protection, Clayboard offered a unique advantage: it could act as a crumple zone to absorb vertical stress while providing a predictable separation layer between the tunnel and the concrete structure above.

To enable this controlled compression, we also proposed our Voidpack irrigation system, which would allow low-pressure water to be introduced after the concrete had cured, stripping away the core resistance and enabling the engineered collapse of the Clayboard panels.

The result?

A lightweight, recyclable, and high-performance void former that helped prevent excess load on the tunnel and dampen rail vibration in the building above.

Want to understand the fundamentals? Read What is a void former used for?

Optimised Clayboard logistics for lightweight construction projects

Before full deployment, the Clayboard void former was trialled and minor adjustments were made to optimise the shipping process. Our standard 2.44m panel length didn’t efficiently fit inside shipping containers, so we sourced a custom fluted polypropylene outer skin, which allowed us to manufacture shorter panels and maximise fill per container.

This small change:

• Reduced shipping costs
• Lowered carbon emissions
• Delivered faster turnaround for the client

The product was manufactured, packaged, and shipped to Brooklyn within two weeks, a tight timeline that showcased our agility and client-first approach.

Once on-site, Clayboard’s lightweight and modular design made it easy to handle and install, even on a busy urban site with limited space and access.

Its recycled paper honeycomb core supported the project’s environmental goals, while the engineered collapse zone ensured lasting protection of the infrastructure below.

Curious how Clayboard compares to traditional EPS systems? Is it better to use compressible void formers?

Why Clayboard was the right void former for this project

This project demonstrated the true value of early collaboration, engineering precision, and product adaptability. Clayboard delivered on all fronts:

Let’s build smarter, together

Working on a sensitive site? Need a lightweight, certified, and environmentally responsible solution for void protection, infrastructure separation, or vibration control?

Our technical team is here to help you specify the right Clayboard void former for your project, whether you’re building in the UK, across Europe, or further afield.

Get in touch with us today to discuss your requirements and explore how Clayboard can support your next build.