The challenge
Exposed concrete soffits — the underside of a concrete floor or deck — are a common cold bridge. Concrete is a dense, conductive material, so an uninsulated soffit loses heat and can run cold enough for condensation to form on its surface. In a cultural venue like The Box in Plymouth, a controlled, comfortable internal environment is part of the building's purpose.
The soffit's surface is uneven and broken up by structural features, beams and service penetrations, which makes a neat board-and-fixing approach awkward and slow. The insulation needed to bond tightly to the concrete and work around those obstructions without leaving gaps or cold bridges.
The ThermoFoam solution
ThermoFoam applied Enverge closed-cell spray foam directly to the concrete soffit. The foam self-bonds to the concrete as it cures, following the contours of the deck and working neatly around beams and penetrations to form a single continuous layer — with no mechanical fixings, no boards and no joints.
The dense, moisture-resistant closed-cell foam insulates the cold concrete and helps prevent the surface condensation an exposed soffit can suffer. Supplied by Duratite as UK distributor of record and certified, it gave a public cultural building a recognised, documented specification.
The result
The concrete soffit now carries a seamless, fully bonded insulating layer that removes a significant cold bridge and improves the thermal stability of the space beneath. The application is clean and continuous around the structural features and is backed by a 25-year manufacturer-backed product warranty.
