Rzeczoznawca, ochrona przeciwpożarowa

"NRO" – an abbreviation known to probably all designers and likely building contractors as well. It is common knowledge that for most buildings, specified building elements are required to be NRO, which essentially means non-fire-spreading. In design documentation, provided it does not escape the designer's attention, it is quite easy to state that all building elements are to be non-fire-spreading. Complications may begin when selecting, at the design or construction stage, the appropriate construction products that meet this requirement. And the ways to satisfy it, along with the relevant classifications, vary depending on whether it is a roof, an internal wall or slab, or an external wall.

In these considerations, a few sentences regarding issues related to external walls. As I mentioned above, in most buildings external walls, like other building elements, are required to be non-fire-spreading. This stems directly from the requirements of the regulation on technical conditions to be met by buildings. Even if this requirement does not apply to a given facility, it is often still better to construct the walls as non-fire-spreading, because otherwise there is a need to increase the distance from other facilities or the boundary of an undeveloped plot. And here it is worth noting that this also applies to single-family houses, although some people think that when it comes to a single-family house, no fire protection requirements apply anymore.

And just to make it not so easy, our national regulations require a special approach to external walls. Namely, with regard to fire spread, external walls are considered separately in terms of fire spread from the inside and separately from the outside of the facade.

And so, in accordance with the provisions of the regulation on technical conditions...: In the case of external walls of a building, including those with insulation and external cladding or with external cladding only, building elements are understood as:1) non-fire-spreading – building elements that are non-fire-spreading under exposure to fire both inside and from outside the building,2) weakly fire-spreading – building elements that, under fire exposure on one side, are weakly fire-spreading, while under fire exposure on the other side, are weakly fire-spreading or non-fire-spreading,3) strongly fire-spreading – building elements that, under fire exposure on one side, are classified as strongly fire-spreading, regardless of the classification obtained under fire exposure on the other side– for which requirements under exposure to fire inside the building are specified in accordance with Annex No. 3 to the regulation, and under exposure to fire from outside the building are specified in accordance with the Polish Standard on the test method for the degree of fire spread by walls.

If we look into the aforementioned annex to the regulation, we will find information that in the case of external walls regarding fire spread from the inside: Non-fire-spreading building elements correspond to elements:– made of products with a reaction to fire class, in accordance with Polish Standard PN-EN 13501-1: A1; A2-s1, d0; A2-s2, d0; A2-s3, d0; B-s1, d0; B-s2, d0 and B-s3, d0;– constituting a product with a reaction to fire class, in accordance with Polish Standard PN-EN 13501-1: A1; A2-s1, d0; A2-s2, d0; A2-s3, d0; B-s1, d0; B-s2, d0 and B-s3, d0, provided that the insulation layer of sandwich elements has a reaction to fire class of at least E.

Weakly fire-spreading building elements correspond to elements:– made of products with a reaction to fire class, in accordance with Polish Standard PN-EN 13501-1: C-s1, d0; C-s2, d0; C-s3, d0 and D-s1, d0;– constituting a product with a reaction to fire class, in accordance with Polish Standard PN-EN 13501-1: C-s1, d0; C-s2, d0; C-s3, d0 and D-s1, d0, provided that the insulation layer of sandwich elements has a reaction to fire class of at least E.

Therefore, it is worth noting, which unfortunately often escapes designers and contractors, but also construction product manufacturers, that for construction products in terms of evaluating fire spread through external walls from the inside, not only is the overall classification of the product important, but also a separate classification of the insulation layer, which must have a confirmed reaction to fire class E; and it happens that despite the proper classification of the product as such, there is a problem because either the insulation layer does not have class E but F, or the manufacturer does not declare the reaction to fire class of the insulation layer.

In the case of evaluating fire spread from the outside, a classification according to standard PN-B-02867:2013-06 *Fire protection of buildings – Test method for fire spread degree by external walls from the outside and classification rules* is required. And here there is often a problem, because especially foreign manufacturers offering products for constructing facades are frequently unaware of this requirement, and surprisingly this problem can be encountered in the case of some manufacturers with a fairly major position in the construction market. According to this standard, a wall can be qualified into one of three classes: NRO - non-fire-spreading, SRO - weakly fire-spreading, SIRO - strongly fire-spreading. This standard also stipulates that in the case of walls in which every component has a reaction to fire class of at least A2-s3,d0, testing does not need to be conducted and the wall is deemed non-fire-spreading.

Thus, only obtaining documents from the manufacturer of a given product confirming the appropriate reaction to fire class regarding fire spread from the inside, a separate classification under the aforementioned Polish Standard regarding fire spread from the outside, and in the case of sandwich products, additionally the reaction to fire class of the insulation layer, allows one to be sure that the applied solution meets the requirements regarding fire spread by external walls.

It is also worth noting that classifications apply to a given product with specific parameters. It happens that, for example, facade cladding of the same type with one thickness will be classified as non-fire-spreading, while with another thickness it will not. Other aspects, such as the mounting method, etc., can also have an influence.

Paying attention to the above aspects before constructing the facade and maintaining a highly developed level of assertiveness when sales representatives assure "Sir, this is suitable and meets all requirements" will help save unnecessary stress and additional costs if an already installed solution had to be replaced. The problem is serious when the documentation does not meet the requirements during the building acceptance inspection, or even worse, when something burns down – then there is no turning back.

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NRO - what does it mean in the case of external walls

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