Metal Soffit Insulation – Derriford District Centre, Plymouth
From failing roof to finished system
The Challenge
Devon Contractors Limited appointed Duratite to deliver a high-performance insulation system for the new Aldi store at Derriford District Centre in Plymouth. The exposed galvanized metal soffit required a robust and fully bonded solution capable of achieving a design U-value of 0.18 W/m²K while maintaining long-term adhesion and surface durability.
Traditional insulation boards were not suitable due to the ribbed steel profile and limited access around the building’s perimeter. To overcome this, Duratite specified a hybrid spray foam system combining Enverge Nexseal LE closed-cell and Enverge Sucraseal open-cell insulation.
Project file
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The Solution — step by step
The Insulation Solution
The system was applied in two stages:
Enverge Nexseal LE (25 mm closed-cell base layer)
Sprayed directly onto the galvanized soffit to create a rigid, moisture-resistant base and permanent bond to the substrate. Nexseal LE provides vapour control, high adhesion strength, and a durable structural coating suitable for exposed environments.
Enverge Sucraseal (160 mm open-cell top layer)
Applied over the closed-cell layer to achieve the specified U-value. The expansive open-cell formulation ensured complete filling of the corrugated steel profile and voids, eliminating air pockets and thermal bridging. Sucraseal’s controlled expansion allowed a consistent depth and smooth finish across the soffit area while contributing to the system’s Class 1 Surface Spread of Flame fire performance.
This hybrid configuration delivered excellent thermal performance, full coverage across the irregular metal deck, and a cost-effective means of achieving the target specification without complex fixing systems or rigid board installation.
Installation & Site Conditions
The installation was completed using scissor lifts, with operatives working at approximately three metres above ground level. Changing weather conditions, including wind and intermittent rain, required strict control of spray operations and the use of containment sheeting to prevent overspray.
Duratite’s installation team carried out continual thickness checks, adhesion tests, and visual inspections to ensure full coverage and curing quality. Spray works were paused during unsuitable weather to maintain material integrity.
All works were undertaken under Duratite’s installation control procedures, including PPE compliance, ventilation management, and height-safety protocols.
Why Nexseal LE and Sucraseal Were Chosen
Duratite selected this hybrid system to combine the mechanical strength and vapour resistance of Nexseal LE with the lightweight, expansive coverage of Sucraseal.
- Nexseal LE (λ = 0.027 W/mK): Provides a dense, closed-cell structure that bonds directly to metal surfaces, offering a continuous vapour barrier and exceptional durability.
- Sucraseal (λ = 0.039 W/mK): Expands to fill every void within the corrugated profile, ensuring full coverage and airtightness while delivering Class 1 fire performance and excellent thermal efficiency at lower cost.
The result is a high-performance, fully bonded soffit insulation system that achieves outstanding thermal, fire, and moisture control characteristics in a single, spray-applied application.
The Outcome
- Achieved the specified U-value of 0.18 W/m²K.
- Provided a Class 1 Surface Spread of Flame fire rating.
- Delivered a seamless, airtight barrier with no voids or air gaps.
- Maintained strong adhesion to the galvanized substrate without fixings.
- Offered a cost-efficient solution by combining open- and closed-cell technology.
- Completed installation with minimal disruption and excellent visual uniformity.
The finished soffit system provided long-term protection against condensation and heat loss, while delivering a clean and durable surface finish suited to the exposed perimeter areas of the retail unit.
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