Class 0 is a no-go for fire safety of high-rise buildings

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When discussing the fire safety of high-rise buildings in the UK, there is a great deal of confusion on the requirements for facade cladding panels. Central to this situation is the so-called ‘Class 0’, stemming from outdated national building regulations. Class 0 is still used in regulations to define the quality of facade cladding products, even while the mandatory European system on fire classification requires other, stronger specifications. This article discusses why it is important to stop using Class 0 in determining fire safety of facade cladding products.

The Euroclass system defining the fire performance of building products came into existence in the year 2000. It was introduced by the European Union (EU) to remove trade barriers between individual member states. Before the introduction, manufacturers had to test building products in individual countries. All of them had their own unique testing methods to define the fire performance of a product.

The European Reaction to Fire classification consolidated test standards from EU member states into one common test standard – The Euroclass system

For instance, a company from Germany which wanted to sell facade cladding panels in the UK and France, had to get their products tested in both countries in order to obtain approval to enter these markets. The EU solved this situation by introducing a classification system that applied to all member states. However, this created new problems in streamlining existing national regulations with this Euroclass system.

ExtraCare Longbridge in Birmingham (United Kingdom) with Rockpanel Woods FS-Xtra facade cladding

What exactly is Class 0?

In the UK Building Regulations on fire safety (1991), a classification was introduced for materials used in wall and ceiling linings to determine the surface spread of flames, with Class 4 being the worst and Class 1 being the best (the least distanced and slowest spreading of flames). Class 0 indicates a Class 1 spread of flames and also takes into account the (limited) amount of heat released from the surface of a product.

When the Euroclass system was introduced, countries such as the UK faced a transition period where both the existing national standards were referred to alongside the mandatory harmonised European classification. In UK building regulations, although only meant to be a transition period, both systems were used alongside each other, a situation that exists still to this day. This causes serious problems, because Class 0 simply does not indicate the same performance as the Euroclass system does.

Class 0: not comparable to the Euroclass system

The Euroclass system classifies the behaviour and contribution of construction materials in a fire. These products are rated A1-F, dependent upon the contribution to the fire load, with Classes A1 & A2 being the best (non or limited combustibility) and further classifications of B-F (combustible).

A Euro classification of F is the weakest (unacceptable fire behaviour) and either is not tested, does not meet the requirements of the higher classes or the manufacturer has decided not to declare the fire properties for the product. This is an important difference when making comparisons with the UK Class 0, which indicates only the surface spread of flames, not the combustibility or contribution of the product itself in the event of being involved in a fire.

In other words, Class 0 says nothing about the combustibility of the material when a fire occurs.

Refurbishment three high-rise residential towers, The Crofts in Birmingham, United Kingdom with Rockpanel Colours in FS-Xtra grade

Because of this difference, there is an important point to make. All too often, Class 0 is being compared to Euroclass B, because both are mentioned in existing regulations. However, Class 0 is not, and can never be, comparable to a Euroclass system Class B. Two different conditions are measured here: National Class 0 measures the spread of flame and the amount of heat release from the surface of a product.

The Euroclass system measures (via sbi-tests, Single Burning Item) flame spread, ignitability, amount of heat, smoke & toxic gas release, whether the product melts, drips or chars. This is more important, because the Euroclass system focuses on the combustibility of materials, not (just) the spread of flames. It is possible that a product, classified as Euroclass B, also has the characteristics of a Class 0 product, but never the other way around. As explained, the subject of testing of both classifications (national and European) differs, as well as the size of testing.

Say no to Class 0

The choice for a Class 0 product might be prompted by the (false) comparison to Euroclass B. However, as we have seen, this product may not even achieve a Euroclass B. Furthermore, using Class 0 as a benchmark may mean that a combustible product is specified.

If unsure of the type of facade cladding for high-rise buildings and their fire performance qualities, it is best to avoid risks altogether and simply choose non-combustible (Euroclass A2 or better) products. Design out the risk and be assured a building will always comply to future building regulations.

Beaumont Court and Richmond House in Southend on Sea, Essex (United Kingdom) with Rockpanel Stones FS-Xtra facade cladding

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