Spray Foam Fire Protection: How Foam, Primer and FRED Achieve Class B
Spray foam insulation seals and insulates in a single step, but on its own it is combustible — untreated polyurethane foam typically classifies only to Euroclass E under BS EN 13501-1. That is why building control bodies and insurers increasingly require a fire-rated thermal barrier over any exposed spray foam. FRED provides that thermal barrier — and, applied as part of the right build-up, brings the foam up to a Class B reaction to fire.
Why exposed spray foam needs a thermal barrier
Polyurethane and PIR spray foams are excellent insulators, but they ignite and spread flame readily when left exposed. Under BS EN 13501-1 untreated foam typically classifies as Euroclass E. Wherever foam is left on show — in lofts, plant rooms, warehouses, garages or timber-frame voids — a tested thermal (ignition) barrier is normally required so the assembly satisfies Approved Document B, building control and insurers.
What a thermal barrier coating does
A thermal barrier coating such as FRED is intumescent: in a fire it swells into a thick insulating char that shields the foam beneath, delaying ignition and slowing flame spread. That buys critical time for occupants to escape and for the fire service to respond, and stops the insulation becoming fuel. For the underlying science, see Intumescent Paint Explained.
The Class B build-up: foam + primer + FRED
Getting exposed spray foam to a Class B reaction-to-fire classification is about the whole build-up, not a single coat:
- Spray foam — the insulation substrate (Euroclass E on its own).
- Supergrip FR (fire-rated primer) — a coat of Intelligent Membranes' fire-rated Supergrip FR primer over the cured foam gives FRED a sound, consistent surface to key into, so the intumescent layer bonds and performs as tested.
- FRED intumescent coating — applied over the primer at the specified wet-film thickness to form the fire-protective barrier.
Together, foam + Supergrip FR + FRED forms a build-up that achieves a Class B reaction to fire — turning a combustible insulation layer into a compliant, fire-protected element of the building fabric.
FRED's certifications
FRED is certified Class A2-s1,d0 under EN 13501-1 — limited combustibility, little to no smoke (s1) and no flaming droplets (d0). It also carries a 25-minute Warringtonfire rating, tested on a load-bearing timber-frame wall (8 kN per linear metre) to BS EN 1365-1:2012. That gives you documented, third-party evidence to hand to building control.
How FRED is applied
- Prime the cured spray foam with Supergrip FR, our fire-rated primer.
- Spray FRED with an intumescent spray machine — Intelligent Membranes recommends a TriTech T5 or a machine of similar specification — to the specified wet-film thickness.
- FRED is for internal use; for external applications, follow your fire engineer's specification and local building regulations.
- Available in white and grey — call the team to discuss colours.
Part of a wider airtight, fire-safe system
FRED also works alongside Intelligent Membranes' airtightness products. Used with Passive Purple on 9mm OSB, the FRED + Passive Purple build-up achieves a Class B rating with up to 30 minutes of fire protection — so your fire, airtight and vapour-control layers work together rather than against each other. See Fire Protection for Timber Frame and Spray Foam.
FAQ
Does spray foam always need a fire coating? Where foam is left exposed and forms part of the fire strategy, a tested thermal barrier is normally required. Foam concealed behind a fire-rated lining may be treated differently — always follow your fire engineer and the relevant test scope.
What fire classification does FRED give? FRED is classified Class A2-s1,d0 to EN 13501-1, and over spray foam with a Supergrip FR primer the build-up achieves a Class B reaction to fire. Always confirm the classification required by your project's fire strategy.
Can FRED be left on show? Yes — it can be finished neatly; see our white intumescent option.
Specifying a thermal barrier over spray foam? Explore FRED or talk to our technical team about your build-up.