Considerations on metal deck roof with insulation

Fuente: Cadena Ser


This post is a translation of a post written by Antonio Galán on November 2016 and it is based on his experience as fire safety consultant. (Original post in Spanish can be read on the following link:

A couple of weeks ago, during the development of a project, my client had to select an insulating material for the execution of a metal deck roof with insulation. He found several options but was not sure about the technical and commercial information received, so he asked me to help him to make an objective technical comparison away from commercial interests from the point of view of reaction to fire. As consequence as my work, my client got to know and understand perfectly the criteria to take into account, for this reason I find it interesting to share on my blog the aspects that were useful to my client.

Legal Requirements

In the current legislation in Spain, a metal deck roof with insulation may be subject to the basic document of fire safety in case of fire of the technical building code (CTE DB-SI) and / or fire safety regulations in Industrial facilities (RSCIEI). Both legislations take as reference two fire risk assessments:

  • Evaluation of the roof exposed to the external fire.

The evaluation of the external fire considerates as reference scenario the eventual fall of flaming droplets or debris on the metal deck roof with insulation that could come from a fire of a near building. The classification will be done according to the standard EN 13501-5 and the test method required in Spain is CEN / TS 1187 method 1.

  • Evaluation of the roof to the internal propagation of a fire.

The evaluation of internal propagation is based on the beginning and subsequent spread of a fire inside a room. The reference classification standard would be EN 13501-1 and the required test methods would be the SBI test (EN 13823) and the small burner test (EN ISO 11925-2).

In the evaluation of external fire, construction systems are tested and classified, not individual materials. The best way to evaluate the behaviour in case of fire is to attempt to reproduce the end use application.

The evaluation of the internal propagation of a fire has to be carried out simulating the end use application as best as possible. This point is showed in and is thus included classification standard for reaction to fire (UNE-EN 13501-1).

End use application

The thermal insulation products have its own standard for CE marking. The aspects related to the reaction to fire are based on the standard EN 13501-1. In addition, the insulation products have a mandatory standard which shows the instructions for mounting and fixing the reaction tests to fire (EN 15715). This standard indicates that the product must be tested as placed on the market is without any non-integrated installation means, e.g. : glues, sealants, etc.

But the in the reality, this kind of products rarely are installed naked in their end use application and therefore the previous classifications do not provide relevant evidence regarding their fire behaviour, because they do not reflect the reality.

The standard EN 15175 offers the possibility of testing in a complementary way and according to the end use application through 4 reference scenarios.

Table 1. Standard test configurations of standardised assemblies. Source: EN 15715.

Through standardised assembly number 3, it will be possible to reproduce a metal deck roof with insulation in a reaction to fire tests. The Euroclasses achieved by the thermal insulation products will represent a classification in end use application.

Obviously, this test offers a more realistic classification on the fire behaviour of the metal deck roof with insulation. On the contrary, a classification provided by a naked product would only be applicable if the metal deck roof with insulation were installed with the insulation material naked


In the tests to evaluate the exposure to an external fire the production of smokes is not measured. But in the SBI test, necessary to know the internal propagation of the fire, the opacity of the smoke is evaluated quantitatively. The importance of this type of measurement lies in the possible obscuration of the escape routes in case of fire.

However, in case of fire, the amount of smoke depends on the product and the characteristics of the fire (combustion temperature, oxygen concentration, ventilation, etc.).

In addition, it is necessary to know that all insulating products produces smokes, another aspect will be the degree and its colour. Even the mineral wool products which are made of binders and / or adhesives produces smokes. In fact, several studies have shown that some mineral wool products in the pre-flashover phase emit pyrolysis gases in a very similar way to products with synthetic cores.

Fire load

The fire load of a metal deck roof with insulation can be calculated using the test method EN ISO 1716. For this calculation is considered the whole metal deck roof with insulation, not only the insulation material. This test method allows us to obtain the gross heat of combustion (PCS) of a product or system in MJ/kg and in MJ/m2. The PCS in MJ/kg has its importance to effects of classification affects but it should not be forgotten that the weight factor is a relevant fact in this type of construction and for that reason the most appropriate to use the PCS in MJ /m2. In fact, in the RSCIEI, the expression for the calculation of the load density specifies the PCS per unit area. Also, the CTE DB SI uses this unit to show the fire load density.

In addition, it should be taken into account that the fire load represented by the content is much greater than the fire load of the insulation products, both in industrial facilities and other uses like offices, dwellings, hospitals, theatres, etc..

Fire resistance

Finally, I will make reference to the resistance to the fire to clarify what is and in what consists because in my case, was used in the wrong way. Fire resistance is the time that a construction system is able to guarantee one or several characteristics of performance. The most common features are loadbearing capacity (R), thermal insulation (I) and integrity (E). It would also be possible to guarantee other types of performance depending on the type of construction and its function, such as radiation (W), mechanical action (M), self closing (C), etc.

In the case of a metal deck roof with insulation is to guarantee fire resistance, that system must be tested through the whole system, not just partial elements of the system.

But the fire resistance never values the melting temperature of a product. Therefore, it is not possible to say that a product has a fire resistance of X ° C, at least in the field of fire resistance of the building systems.


The installation of thermal insulation products does not result in a high fire risk if they meet with the applicable current legislation, because the fire safety of an enclosure does not depend only on the reaction to fire of a product but it would have to take into account other measures, such as active and passive protection measures, prevention activities, etc. To obviate this fact about the fire safety, it would be really dangerous.

We must know that, historically, fires have affected installations with all types of thermal insulation products, even mineral wool products. But it must be emphasized that insulation products will never be the source of the fires.

Diseño de Instalaciones de Protección contra Incendios (PCI)