Two panels standing side by side look the same: the same rib, the same colour, the same thickness. The difference cannot be seen, because it lies in the steel thickness, the core density and the declared values. This article is about where that difference hides and how it is checked.
What is a tolerance and what is a defect?
No production holds a single figure exactly. Steel thickness, core density and panel dimensions come out within a range; the product standard EN 14509 defines how those ranges are set and how performance is declared.
The problem is not the tolerance itself. The problem is a declared value not being met in reality: steel that says 0.50 mm on paper turning out thinner on site, a core below the declared density, or the insulation thickness being presented mixed up with the total thickness of the panel.
The three places the difference hides
Steel thickness
The stiffness and the load behaviour of the envelope come largely from the steel. The two faces can differ in thickness, and a quotation can carry a single number. The question is clear: how many mm is the inner sheet, and how many the outer.
Core density
Density relates to bonding, to compressive strength and to how the section behaves over time. On polyurethane cored products, the declared band runs from 30-35 to 48-52 kg/m³ depending on the product; on rock wool cores it is 90-130 kg/m³. The value is written on the product card; if it is not, ask.
Insulation thickness and total thickness
These are not the same thing. On a ribbed roof panel the total height includes the rib height. The comparison is made on the insulation thickness; otherwise the panel that looks thicker in fact insulates less.
The most common mistake with fire class
The fire class depends on the core and is given with a report:
| Core | EN 13501-1 class |
|---|---|
| Rock wool, hybrid | A2-s1-d0 |
| PIR | B-s1-d0 |
| PUR | B-s2-d0 |
| EPS | no published class |
The same panel is B-s2-d0 with a PUR core and B-s1-d0 with a PIR core. On a quotation that says "PUR-PIR", if it is not clear which core will arrive and which one the class was given for, the class counts as undeclared.
The second mistake is confusing class with resistance. Fire class is the reaction of the material to fire (EN 13501-1); fire resistance is the resistance of a building element in minutes (EN 13501-2) and requires a separate test report.
How to check: the declaration, not the catalogue
A catalogue is a promotional document; what binds is the declaration of performance and the test report. Nuhpanel's documents stand open in the Library section.
There are also three simple checks that can be made on site:
- Measure the insulation thickness from the panel section
- Check the steel thickness with a micrometer
- Compare the product code on the delivery note with the quotation and the specification
The ethical side: writing nothing is also a declaration
Presenting an unknown value as if it were known misleads just as much as writing a wrong one. On this site the fire class field is empty for products with an EPS core, because no EN 13501 class has been published for them. An empty field is more honest than an estimated class and does not send whoever writes the specification in the wrong direction.