Almost every fire-resistant product carries a code: EI 30, EI 60, EW 30, R 120. They determine whether a product suits your situation, yet they are often misread. This article explains how the classifications are structured and how to determine which one you need.
The letters
The classification derives from the European standard NEN-EN 13501 and consists of letters describing the performance, followed by a number in minutes.
| Letter | Stands for | What it means |
|---|---|---|
| R | Resistance (load-bearing capacity) | The structure keeps bearing load. Applies to load-bearing elements: columns, beams, floors. |
| E | Etancheite (integrity) | No flames or hot gases pass through. |
| I | Isolation (insulation) | The unexposed side stays cool enough: an average rise of no more than 140 degrees. |
| W | Radiation | Transmitted radiation stays below a limit value. Lighter than I. |
| S | Smoke (smoke tightness) | Limited smoke leakage. Crucial on escape routes. |
The number is the time in minutes during which all the stated criteria are met. EI 60 therefore means: sixty minutes both flame-tight and insulating.
The distinction that matters most: EI versus EW
This is the confusion that most often costs money in practice. EI holds back the heat: you can stand right beside it without the temperature on your side rising dangerously. EW lets heat radiation through in part and is therefore a lighter - and cheaper - requirement.
EW products, often fire-resistant glass, are attractively priced but are not permitted everywhere. On an escape route where people have to walk past the separation, the radiation transmitted by an EW pane may be too high. Whether EW suffices depends on the occupancy function and on the distance to where people are. This is not a choice to make on price.
Which classification applies where?
The required value follows not from the classification itself but from the WBDBO requirement of the Bbl for that specific separation. Broadly:
| Situation | Typical requirement |
|---|---|
| Between two fire compartments | EI 60 for the separation as a whole |
| To an adjacent building or plot | EI 30 per building |
| Door in a 60-minute separation | Often EI₂ 30-S, sometimes EI₂ 60-S |
| Load-bearing structure, commercial buildings | R 60 to R 120, depending on height and function |
| Sub-compartment in healthcare | 20 to 30 minutes, plus smoke resistance |
Note the notation EI₂ for doors: the subscript 2 refers to how the temperature rise on the unexposed side is measured. EI₁ is the stricter variant. In the Netherlands, EI₂ is generally applied to doors.
Why a door may be lighter than the wall
This surprises many building owners: an EI 60 wall often contains an EI₂ 30 door. That is not an error. The WBDBO is determined under NEN 6068 across the separation as a whole, with the contribution of each component weighed in. A door occupies a limited part of the surface, and the standard permits that part to have a lower classification as long as the total meets the requirement. Your fire safety consultant or the permit drawing will confirm what is permitted for your separation.
The pitfall: a classification applies to the tested combination
A classification belongs to a complete, tested system - not to a standalone product. Fire-resistant glass with EI 60 achieves that value only in the frame system, with the glazing gaskets and hardware it was tested with. The same pane in a different frame has no valid classification, even if the glass is identical. The same applies to seals: the system was tested in a particular wall type with a particular build-up, and outside that the value lapses.
This is a common reason for rejection at inspections: on paper the product is right, but the application falls outside the tested build-up.
Not sure which classification applies to your building? An inventory maps the required and the actual value for each separation. Also read the explanation of the WBDBO requirement.
Frequently asked questions
Thirty minutes flame-tight (E) and insulating (I): no flames or hot gases pass through and the temperature on the other side rises by no more than 140 degrees on average. EI 60 is the same for sixty minutes.
EI holds back the heat; EW lets heat radiation through in part and is therefore a lighter requirement. EW is cheaper but not permitted everywhere; on escape routes the transmitted radiation may be too high. Have what is permitted assessed per situation.
Often yes. The WBDBO is determined under NEN 6068 across the entire separation, in which a door occupies a limited part of the surface. Whether it is permitted in your situation follows from the calculation or the permit drawing.
No, to the complete tested combination. Fire-resistant glass achieves its classification only in the frame system it was tested with. A different frame means no valid classification, even with identical glass.
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