Case Study – Sheet Piling Insulation | Bloor Homes, Sheffield
From failing roof to finished system
The Challenge
Duratite were appointed by Cook Group Limited, the principal groundworks contractor for Bloor Homes, to deliver a high-performance insulation system to newly installed AZ 18-700 steel sheet piles forming part of a below-ground retaining structure at the new Bloor Homes development in Sheffield.
The design team required a solution that could deliver a consistent U-value of 0.18 W/m²·K, maintain long-term adhesion to the corrugated steel profile, and provide both moisture protection and thermal stability in a challenging subgrade environment.
After evaluation of various build options, Cook Group and Bloor Homes selected Enverge Nexseal LE closed-cell spray foam as a superior alternative to traditional shotcrete insulation systems, due to its speed of application, enhanced thermal performance, and permanent bond to steel substrates.
Project file
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The Solution — step by step
System Specification
- Substrate Preparation: The steel piles were prepared by mechanical cleaning and verification of surface temperature (>5°C) and dryness before application.
- Spray Application: Enverge Nexseal LE was applied in controlled passes of up to 100mm per layer, with a minimum 15-minute cooling period between applications to ensure complete curing.
- Low Exothermic Reaction: The advanced low-exotherm formulation of Nexseal LE allows for thicker, faster sequential passes without risk of scorching or shrinkage, reducing total spray time and allowing project timelines to be accelerated compared with conventional polyurethane foams.
- Build-Up: An average thickness of 420mm was achieved within the sheet pile rebates (approx. 29 rebates at 684mm x 2.4m high).
- Face Layer: A uniform 18mm surface coat was applied over the filled rebates, ensuring full continuity of the thermal barrier.
- Protective Coating: The cured foam was finished with ET150 spray-applied vapour barrier (grey), providing UV resistance, vapour control, and a durable site-protective coating.
Why Nexseal LE Was Chosen Over Shotcrete
While shotcrete has traditionally been used for lining steel or concrete retaining walls, both Cook Group Limited and Bloor Homes identified several key advantages of Nexseal LE closed-cell spray foam for this application:
- Superior Thermal Efficiency: Nexseal LE’s λ-value of 0.027 W/m·K enables the design to achieve a U-value of 0.18 W/m²·K without the excessive thicknesses required for shotcrete systems, providing improved energy efficiency within the same space.
- Faster Installation: The spray-applied nature of Nexseal LE eliminates shuttering, curing, and reinforcement delays associated with shotcrete, allowing for rapid installation across complex corrugated profiles.
- Exceptional Adhesion: Nexseal LE chemically bonds to the steel substrate, forming a rigid, monolithic insulation layer with no risk of delamination or mechanical failure — a crucial factor in below-ground waterproofing performance.
- Reduced Structural Loading: The lightweight foam reduces overall dead load on the piling structure compared with dense concrete-based alternatives.
- Integrated Vapour Control: The system inherently resists moisture and vapour ingress, removing the need for separate membranes or cementitious sealing layers.
The Outcome
- Thermal Conductivity: 0.027 W/m·K
- U-Value Achieved: 0.18 W/m²·K
- Closed-Cell Content: >95% (vapour impermeable)
- Application Rate: Accelerated due to low-exotherm chemistry enabling multiple rapid spray passes
- Protective Finish: ET150 spray-applied vapour barrier (grey) for UV and surface durability
The Enverge Nexseal LE system delivered outstanding performance in every key category — thermal resistance, adhesion, durability, and water tightness — while significantly shortening programme duration and site disruption.
Installed by VP Foam Spray in September 2024, the completed insulation works provided a continuous, high-density closed-cell thermal barrier to the full height and profile of the steel sheet piling.
The result is a fully bonded, thermally efficient retaining structure designed to meet Bloor Homes’ sustainability and performance targets, offering long-term insulation stability, water resistance, and substrate protection.
By specifying Enverge Nexseal LE, Cook Group Limited successfully eliminated the need for shotcrete, improved installation efficiency, and delivered a durable system that meets the U-value target of 0.18 W/m²·K — setting a new benchmark for modern piling insulation design in residential construction.
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