Building material classes

What do the building material classes have to do with the city fire in Rome in 64?

To anticipate: the building material classes have a lot to do with the city fire in Rome under Nero. What exactly? Please be patient for a moment - we'll get to this question in a moment.

Why are there building material classes? And why are they important? This article on the subject of building material classes revolves around such elementary questions. First of all, it's about understanding the idea behind the building material classes. In order not to put you off immediately, we will only take a look at the legal and normative situation in a subsequent article. Unfortunately, it is somewhat opaque. But it doesn't help, applicable law must of course be implemented. But let's start slowly.

What not awaits you here?

The point here is not to show what feels like a thousandth table for the building material classes. You can find them everywhere. I find it more interesting to look behind this table. To explain why it is valuable. Of course, you will still find the table with the building material classes below. That's part of it. By the way, the child has several names. The term fire protection class means the same as building material class.

Why are there building material classes?

We will first address the question of why there are building material classes at all. You may be familiar with the frequently asked question of whether we can learn from the past. Yes we can! At least as far as the topic of building material classes is concerned. In ancient and medieval times, fires engulfed many cities. Rome, Regensburg, Rotterdam - the list of city fires is long. Luckily it's different today. Large city fires are rare and often a result of natural forces such as earthquakes. What has changed?

In the past, people lived in houses made of wood and straw. Today we live in houses with solid walls and a so-called hard roof. So in construction we use materials that are non-combustible. Or at least poorly combustible. Not everywhere and for every member, but at the crucial points. This significantly reduces the risk of fire. Which building materials we choose belongs to the so-called structural fire protection.

The downside, as is often the case with preventive measures, is that they hardly raise awareness. It's kind of like airplane pilots. The press applauds the pilot, who just manages to save the distressed plane with an emergency landing. Nobody talks about the thoughtful pilot who avoids risks as much as possible.

We want to live safely. For this it is advisable to distinguish the building materials. History teaches us that city fires are dangerous. Therefore, with the building material classes, we distinguish whether and how the building material burns. So the building material classes are important and worth a closer look.

Flammability of substances

Which substances burn?

We want to avoid fires. To achieve this, we use few combustible materials. But which ones are they? Of course, a combustible substance alone is not enough to start a fire. Otherwise our environment would be permanently in flames. The so-called combustion triangle applies. A fire needs sufficient oxygen in addition to a combustible substance. In addition, the temperature must be high enough to ignite the substance.

Most organic compounds are flammable. We don't want to drift into chemistry. Therefore only briefly the essential connection. Organic compounds are made of carbon. When sufficient oxygen is available and the ignition temperature of a substance is reached, a chemical process takes place. The carbon (C) combines with the oxygen (O2) to form carbon dioxide (CO2). What are organic compounds? Almost everything that surrounds us in our everyday life:

• Paper;
• wood;
• textiles;
• straw;
• car tire;
• fats;
• spirit.

Which substances do not burn?

Let's turn the question around in our minds. Which substances cannot be ignited and are therefore not combustible? We saw above that many organic matter can burn. Conversely, most inorganic substances are not combustible. These are substances without carbon. Some examples of inorganic and non-combustible materials are:

• Metals such as silver, gold and platinum;
• salts, such as sodium chloride (also called table salt);
• minerals.

Are there exceptions?

Unfortunately, there are, and that complicates things. Even most metals burn. Some of these can even self-ignite when finely dispersed (such as steel wool). Some metals burn at low temperatures, such as lithium. It is therefore not a good idea to leave lithium batteries in direct sunlight.

Are there any substances that burn badly?

Yes, there are! Firefighters speak of flame-retardant materials. These are materials that only burn if they are directly supplied with energy by a fire. So they don't burn on their own. Which materials are flame retardant? Below are some examples:

• Cork;
• wood wool lightweight board;
• floor coverings such as oak parquet;
• impregnated fabrics.

Are there materials that burn particularly well?

There are also those and they are called highly flammable. This group includes the following materials:

• Straw;
• paper;
• cardboard.

Which substances burn normally?

The fire protection officer describes everything that is between easily flammable and hardly flammable as normally flammable. These include, for example, the following substances:

• wood with a bulk density of more than 400 kg/m³ and thicker than 2 mm;
• rigid foam thermal insulation panels without flame retardant additive;
• electric lines;
• different plastics.

German building material classes according to DIN 4102-1

Everything that we have looked at in more detail above is summarized in the previous national standard DIN 4102-1 on the "Fire behavior of building materials and members" (in German: ""Brandverhalten von Baustoffen und Bauteilen"") are clearly summarized in the following table. Now it is finally coming, the table announced above. Because the European standards are gradually replacing the national standards, you will also find the designations according to DIN EN 13501-1 on "Classification of building products and building types in terms of their fire behavior". As you can see, there are more classes in the European standard. What I don't show here are other requirements of the European standard for the so-called dripping behavior of building materials in the event of fire. That will be covered in another post.

Where and how are the different materials used?

That would be the dream of every firefighter: if builders only use building materials from the top two rows of the table in the future. But who wants to live in a house made entirely of non-combustible materials? That would be a cool place of stone and concrete.

In order not to plan beyond life, fire protection planners therefore provide for either non-combustible materials or at least flame-retardant materials. The more people use a building, the more important fire safety becomes. Because the risk of fire and possible damage increases. A large number of special ordinances regulate fire protection in public areas of life, for example:

• High-rise buildings;
• meeting places;
• accommodation facilities;
• schools and colleges;
• hospitals.

These are examples of so-called regulated special constructions. There are also unregulated special buildings for which fire protection planners prepare "made-to-measure fire protection" in so-called fire protection concepts. As an example, let's assume that we as firefighters are planning a high-rise building. In this case, the "appropriate" directive would be the so-called high-rise directive. The official designation "Guidelines for the construction and operation of high-rise buildings" is somewhat more cumbersome.

In this guideline alone I find 14 passages that regulate the fire behavior of building materials. In high-rise buildings, for example, the following components must be made of non-combustible building materials: the load-bearing and stiffening components (columns and beams), room-enclosing components (walls), the roof and the floor coverings in necessary stairwells.

You can now definitely see the meaning behind these strict requirements. If there is a fire in a high-rise building, the supports and beams must not fail. That is why they are built from non-combustible materials. Otherwise the skyscraper could quickly collapse. As with the World Trade Center, a great many people could then die. The users of the high-rise must also be able to leave it safely. For this purpose, the escape routes must be free of toxic smoke. For this reason, the floor coverings in the escape routes, for example, may only consist of non-combustible building materials.

Would you like to read more?

If you are interested in the topic, I recommend the following articles:

• In the article above we always talked about building materials. However, a component can consist of different building materials. For example, a reinforced concrete column consists of the two building materials concrete and reinforcing steel. The so-called fire resistance class describes the requirements for the components.
• In the article structural fire protection you will find further information on how a building can be planned that is also safe in the event of a fire.
• The article on constructive fire protection in building construction shows how you can protect columns and beams from heating up, for example.