Concrete Slab Spray Foam Insulation
ThermoFoam sprays Enverge closed-cell foam to the underside of concrete floor slabs and decks over unheated voids, cutting cold-bridging and condensation across commercial and industrial buildings.
Why spray foam for concrete slabs
A concrete slab spanning an unheated void, basement, plant space or open undercroft loses heat downward and runs cold on its underside. That cold surface chills the floor above, draws warmth out of the occupied space, and where humid air meets it, condensation and damp staining form on the soffit and around the slab edge — a classic cold-bridge problem in commercial structures.
Closed-cell spray foam is applied directly to the slab underside, where it self-bonds and cures into a seamless, water-resistant insulating layer. It follows the soffit's downstand beams, service penetrations and irregularities without gaps, warming the concrete above dew point and breaking the thermal bridge in a single sprayed pass that rigid boards struggle to seal cleanly.
The outcome is a warmer floor, lower heat loss through the slab, and a soffit that no longer attracts surface condensation. The continuous layer is well suited to congested undercrofts and plant rooms full of services, supports Part L thermal-performance goals, and the warrantied system carries a 25-year manufacturer-backed product warranty.
The benefits for concrete slabs
Breaks Cold-Bridging
Warms the slab underside so heat stops draining into the unheated void below and the floor above runs warmer.
Stops Soffit Condensation
Lifts the cold concrete surface above dew point, ending the damp and staining that form on exposed slab soffits.
Bonds To Concrete
Self-bonds directly to the slab soffit as it cures, with no fixings drilled into the structural deck.
Seals Around Services
Sprays cleanly around downstand beams, pipework and penetrations that rigid boards leave gapped and bridged.
Supports Part L
Improves the floor's thermal performance, helping commercial refurbishments meet building-regulation targets.
No Floor Disruption
Applied from below to the slab underside, so the occupied floor above stays in use during the works.
Insulating Cold Slab Voids
Where a concrete floor slab or deck sits over an unheated void, plant room or open undercroft, its underside stays cold and drives heat loss and condensation into the floor above. Closed-cell foam self-bonds to the soffit of the slab as it cures, forming a continuous insulating layer that warms the structure and seals the cold bridge.
ThermoFoam applies Enverge closed-cell spray foam (Nexseal LE) to clean, sound slab soffits. Duratite is the UK distributor of record. The foam self-bonds as it cures into a continuous, water-resistant insulating layer that warms the concrete, controls interstitial condensation and breaks the cold bridge across the unheated void below.
- For slab undersides over unheated voids and undercrofts
- Sprayed in-situ — no fixings into the deck
- Seals around beams, services and penetrations
- 25-year manufacturer-backed warranty
Enverge Nexseal LE — verified performance
Typical published values for Enverge Nexseal LE closed-cell foam. Full technical specification →
Specification & compliance for concrete slabs
Sprayed directly to the underside of concrete slabs, car-park decks and metal soffits, closed-cell foam forms one continuous insulated layer with no joints, fixings or cold bridges — the failure points board systems can't avoid on soffits. The foam's low exothermic reaction and strong adhesion make it suitable for overhead application to concrete, Metsec decks and steel framing alike.
Depths of 25–100 mm are specified to hit the required U-value, and where the soffit needs a fire-rated finish the system is completed with DC315 intumescent coating for Euroclass B-s2,d0. The result: warm floors above, no condensation staining below, and a 25-year manufacturer-backed warranty.
From enquiry to warranty
Enquire
Tell us about your concrete slabs & building.
Survey
Free survey of your concrete slabs & condensation check.
Specify
The right system for your concrete slabs.
Install
Approved applicators, minimal disruption.
Warranty
Handover pack & 25-year warranty.
Real concrete slabs spray foam applications
Commercial projects
Richmond House Car Park
Underside of a car-park deck sealed and insulated in-situ.
The Box, Plymouth
Concrete soffit spray foam eliminating cold-bridging.
RBW Carpentry
Cavity-filling spray foam for an airtight commercial partition.
Get a quote for your project
Send us your building details and our technical team will specify the right system and a clear budget. No obligation.
Concrete Slab insulation, answered
Why is the underside of my concrete slab cold and damp?
A slab over an unheated void loses heat downward, so its soffit runs cold. Where humid air meets that cold concrete below dew point, condensation and damp staining form. Insulating the underside warms the surface and stops the problem at source.
Can spray foam be applied to a concrete soffit?
Yes. Closed-cell foam self-bonds to a clean, sound concrete soffit as it cures, with no mechanical fixings needed. It forms a seamless layer that follows downstand beams and service runs, sealing the cold bridge that boards leave gapped.
Will this help with cold-bridging through the floor?
Yes. The sprayed layer warms the slab underside and breaks the thermal path between the occupied floor and the cold void below, reducing heat loss and helping support Part L thermal-performance objectives on commercial refurbishments.
Does the building need to close during the works?
Generally no. Because the foam is applied to the slab underside from the void, plant room or undercroft below, the floor above can usually stay in normal use, subject to access and safe working arrangements on site.
Is the foam certified for this use?
Yes. We install Enverge closed-cell foam (Nexseal LE), supplied with Duratite as UK distributor of record. The system carries a 25-year manufacturer-backed product warranty and suits commercial and industrial slabs.
What depth is applied to a soffit?
Typically 25–100 mm depending on the target U-value and the structure — confirmed at the free survey and specified in writing before work starts.
Is overhead spray application safe for concrete?
Yes — the foam bonds with a low exothermic reaction and no mechanical fixings, making it well suited to concrete slabs, Metsec decks and steel structures.
What fire rating can a sprayed soffit achieve?
With a DC315 intumescent finish the system achieves Euroclass B-s2,d0 — commonly specified for car parks and occupied buildings.
Insulate your concrete slabs the right way
Specialist commercial spray foam, installed UK-wide by the Duratite Group's spray foam specialists.
Book a Free Survey →or call 01208 832 602