Case Study – Contiguous Piling Insulation | Banks Road, Sandbanks
From failing roof to finished system
The Challenge
Situated on the prestigious Sandbanks peninsula, the Banks Road development involved the excavation of a deep beachfront plot to form a new luxury dwelling overlooking Poole Bay. With the site positioned directly above soft coastal sands and exposed to high groundwater influence, a contiguous piled retaining wall was constructed to stabilise the excavation and form the permanent basement perimeter.
Duratite were appointed by CG Fry & Sons Limited to deliver a high-performance insulation and sealing system for the piled retaining wall. The specification required a monolithic barrier to replace the use of shotcrete, which is traditionally sprayed over the pile face to achieve a smooth surface. Instead, Enverge Nexseal LE closed-cell spray foam was selected as a faster, cleaner, and technically superior alternative.
Installation was carried out by Vectis Insulation, a Duratite-approved contractor.
Project file
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The Solution — step by step
Scope of Works
Closed-cell polyurethane foam was applied directly to the face of the contiguous piles, filling the irregular gaps between the concrete sections and forming a continuous insulated fillet. The foam was sprayed from 400mm at the deepest points tapering to zero, averaging 0.07m³ per fillet across the wall.
In total, approximately 5m³ of Nexseal LE was installed—equivalent to 50m² at 100mm thickness. The works were undertaken over multiple sections, including:
- Piling fillets: 80–100mm of closed-cell foam applied to the concrete pile surfaces.
- Pile capping areas: 25mm of foam applied at a 450mm width along 24.5 linear metres.
- Transition zones: Fillet areas around steel beams and retaining tie systems carefully filled and contoured to ensure full coverage and watertight integrity.
Due to the depth variation and pile curvature, spray application required precision layering to maintain tolerance without exceeding the designed thickness or encroaching on structural interfaces.
The Outcome
Enverge Nexseal LE is a 35 kg/m³, low-exothermic closed-cell polyurethane system developed for large-scale applications where controlled curing and dimensional stability are critical. Its unique chemistry allows for uniform lift thicknesses with reduced exothermic heat, preventing surface cracking or delamination even at depths exceeding 300mm.
Key performance characteristics included:
- Compressive Strength: 78 kPa at 10% deflection.
- Thermal Conductivity (λ): 0.027 W/m·K.
- Water Absorption: <1% by volume.
- Adhesion: Exceptional bond to concrete and steel substrates.
- Cure Time: Tack-free in under 60 seconds, full cure within minutes.
The foam created a seamless, vapour-impermeable lining across the contiguous piles, sealing voids and irregularities while simultaneously providing structural reinforcement to the surrounding sand and soil.
The use of Enverge Nexseal LE provided a robust and high-performance solution that eliminated the need for shotcrete. The system delivered a continuous thermal and moisture barrier, improved airtightness, and stabilised the excavation face without the delays and rebound waste associated with concrete spraying.
This installation demonstrated how closed-cell spray foam can serve as an engineered alternative to traditional concrete linings in coastal basement projects — offering faster turnaround, superior sealing, and reduced material handling on challenging beachfront sites.
The completed piling wall formed a clean, rigid substrate ready for waterproofing and structural integration, ensuring the new Sandbanks residence was built on a foundation combining precision engineering with advanced insulation technology.
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