New research from the British Woodworking Federation (BWF) and their Fire Door Alliance scheme found that 27% of the professionals who specify, install and maintain fire doors cite uncertainty over the data needed to evidence performance as a barrier to third-party certification. Cost was cited more often, by 29%, down from 42% in 2023. The evidence gap is the more awkward of the two. Cost is a commercial judgement, but not knowing what proof to ask for is something else.
That study looked at doorsets. The same question applies with more force to glazed screens, because the certified item is never the glass alone. It is the assembly: frame, glass, beads, gaskets, seals, ironmongery and the junctions where the screen meets the structure. Change one element and the tested configuration no longer describes what is installed.
Integrity, insulation and the gap between them
A fire-resisting screen does two separate things. The first is holding the fire back, keeping flame and hot gases on one side for a stated period. The second is stopping heat from passing through. A screen can stay sealed while the face on the safe side grows hot enough to ignite what sits against it, or simply too hot to walk past.
Under BS EN 13501-2 those are two separate classifications. E covers integrity alone. EI covers both, adding a limit on temperature rise across the screen.
The distinction matters because the two get used loosely. A screen described as offering 60 minutes tells a specifier little. An E60 screen and an EI60 screen behave differently in an escape corridor, cost differently, and carry different implications for adjacent construction. Where a screen forms part of a protected route, the insulation question needs answering explicitly rather than inferred from a headline figure.
What a certificate covers, and what it doesn’t
A fire test produces a report describing one configuration, tested one way. The classification report turns that into a rating. Neither covers every variant a project needs. That is the job of a field of application assessment, which sets out the range the tested evidence can reasonably extend across: maximum pane sizes, frame dimensions, glazing methods and permitted variations.
Third-party certification adds a further layer. Schemes such as Certifire assess the test evidence, define the certified scope and audit factory production control continually, so what leaves the factory matches what was tested. A one-off test proves a prototype performed. Ongoing surveillance suggests the next one will too. So a rating quoted without a certificate reference and a defined scope means little. It might be accurate, but there is no way to tell from the datasheet alone.
How openly a manufacturer publishes that material is a reasonable indicator in itself. Radii Planet Group, for example, publishes the tested scope for each system alongside the specification downloads for every rating variant, so the evidence can be checked before a system is committed to, not during technical submittals. Certificate numbers, the rating range they cover and the NBS output all sit in one place.
Where that information proves hard to obtain, the difficulty is itself informative.
The details that fall outside the datasheet
Several parts of a glazed screen sit outside what product literature covers.
Ironmongery
Hinges, closers, locks and handles all affect doorset performance and must have been tested in the configuration proposed, on both the fire and protected sides. Substituting a similar looking handle late on can invalidate the evidence for the entire doorset.
Deflection heads
Where a screen meets a slab that will move, the head detail must absorb that movement while maintaining the rated barrier. A head that was not part of the tested assembly is an untested detail in a certified screen.
Floor void
In fit-outs with raised access floors, the compartment line continues below the finished floor. If the rated screen sits above an unsealed gap, no amount of certification above floor level changes that.
What to ask for before Stage 4
Three requests cover most of it. Ask for:
- The certificate number and certifying body, not a logo on a brochure.
- The classification report reference and the field of application it supports.
- The proposed configuration, including ironmongery and junction details, and whether it falls inside that scope or relies on a separate assessment.
Raised at Stage 4, these are routine queries that shape the specification while it is still open. Left until materials are ordered, they become a variation, and pressure runs towards accepting an assessment rather than changing the system.
Competence over product
Approved Document B has been under continuous review by the Building Safety Regulator since December 2024, with further amendments due at the end of September. The direction is consistent: less reliance on assumption, more on demonstrable evidence.
For glazed screens, that means treating fire performance as a property of a complete assembly with a paper trail behind it, rather than a number attached to a pane. The specification that survives scrutiny tends to be the one where somebody asked for the evidence early and read it.