SCL and Cast-in-situ lining

Sprayed concrete lining

We are a market-leading Sprayed Concrete Lining (SCL) specialist contractor, recognised for delivering safe, high-quality tunnel linings in some of the most demanding ground and environmental conditions. SCL is widely acknowledged as one of the most technically challenging activities in tunnel construction, requiring precise control of materials, equipment, geometry and workmanship.

Our accumulated experience, specialist plant and highly trained workforce place us in a strong position to support projects from early design input through to final lining completion. Our SCL capability spans primary and secondary applications, temporary and permanent works, and complex geometries including enlargements, junctions and caverns. We work closely with designers and clients during Early Contractor Involvement (ECI) to advise on buildability, sequencing, thickness optimisation and quality control, ensuring safe excavation support and long-term asset performance. Our operators are trained to the highest standards and supported by advanced technologies, including computer-assisted boom control, laser scanning and real-time profile verification. Virtual reality and simulator-based training further enhance safety, consistency and ergonomic performance, allowing our nozzlemen and operators to maintain precision while reducing fatigue and manual handling risks. The result is a controlled, repeatable and high-quality lining solution delivered safely and efficiently.

Spray applied secondary lining

Where a sprayed solution is selected for the permanent works, we deliver spray-applied secondary linings that provide structural capacity, durability and finish quality in a single integrated process. This approach can offer programme efficiencies and enhanced flexibility, particularly in constrained or irregular tunnel geometries.

Our expertise ensures accurate thickness control, surface finish and bond performance, supported by digital scanning and verification techniques. Material selection and mix design are carefully controlled to meet structural, durability and fire performance requirements. The sprayed secondary lining is seamlessly coordinated with waterproofing systems, reinforcement and service interfaces to achieve a robust and compliant permanent lining solution.

Cast In-Situ secondary lining

For tunnels requiring a traditional cast in-situ secondary lining, we provide full delivery using proprietary travelling formwork systems or bespoke timber shuttering, depending on tunnel size, geometry and programme requirements. Our experience covers a wide range of tunnel diameters and lengths, including straight drives, curves, enlargements and transitions.

Proprietary formwork systems are used to achieve high productivity, consistent geometry and excellent finish quality on long or repetitive tunnel sections. Where non-standard geometry or local constraints exist, bespoke timber shuttering is designed and constructed to suit the specific requirements of the works, ensuring accuracy and constructability without compromising quality.

Our teams manage all aspects of reinforcement fixing, concrete placement, curing and strike, with strict controls on tolerances, surface finish and interface detailing. Integration with waterproofing systems, drainage and embedded items is carefully planned to ensure durability, serviceability and long-term asset performance.

Tunnel waterproofing (membrane and spray applied)

Effective waterproofing is critical to the durability and performance of underground structures. We provide comprehensive tunnel waterproofing solutions, tailored to ground conditions, groundwater pressures and design life requirements. Our experience covers both traditional sheet membrane systems and modern spray-applied waterproofing technologies.

Membrane systems are installed with meticulous attention to detailing, including interfaces at construction joints, penetrations, drainage elements and terminations. Where programme, geometry or access constraints exist, we also deliver spray-applied waterproofing systems that provide a fully bonded, seamless barrier, reducing the risk of water tracking and simplifying installation in complex profiles.

Our teams understand the importance of integrating waterproofing with excavation sequencing, primary lining tolerances and secondary lining construction. Quality assurance is embedded throughout installation, with inspection regimes, testing and verification to ensure long-term resistance to water ingress and compliance with specification requirements.