When constructing a new building, there are many important aspects to consider. One of these aspects is fire protection. To ensure this and meet the legal requirements, the characteristics of the various building classes must always be taken into account. We have summarized for you which ones there are and what they mean.
The importance of building classes
Different buildings also have different fire protection requirements. Which building materials are approved for the building envelope depends on which building class the structure belongs to. The higher the building class, the higher the fire protection requirements.
In the Model Building Code (MBO), the building classes are defined as a function of the building height and the existing usage units. The height is measured from the ground surface to the top floor edge of the uppermost storey. A usage unit is understood to be contiguous building areas such as an apartment, offices, business premises or practices.
What are the building classes?
Buildings are divided into building classes 1 to 5. The classification depends on the height of the building and the number and size of the existing utilization units.
What is the Model Building Code?
On October 31, 1959, the first Model Building Code (MBO) was introduced by the ARGEBAU (Arbeitsgemeinschaft der Bauministerkonferenzen – Working Group of the Construction Ministers’ Conferences) of the ministers of the federal states responsible for construction, housing and urban development.
The MBO is intended to standardize the individual building codes of the federal states and lead to greater clarity. It is also referred to as the standard or minimum building code. The current version of the MBO dates from 2002 and was last amended by a resolution of the Conference of Building Ministers in September 2019. Unlike the state building codes, it is not a law, but serves as an orientation framework for the building code laws of the respective federal states.
Building classes table
For a better overview we have summarized all building classes with their characteristics in this table:
| building classes | Building type | Building hight | Units of use (UU) | Area |
| Building class 1 | Freestanding buildings | ≤ 7 meters | ≤ 2 UU | Insgesamt ≤ 400m2 |
| Freestanding buildings used for agriculture or forestry | ||||
| Building class 2 | Buildings | ≤ 7 meters | ≤ 2 UU | total ≤ 400m2 |
| Building class 3 | Other buildings | ≤ 7 meters | ≥ 2 UU | total ≥400m2 |
| Building class 4 | Buildings | ≥ 7m ≤13 meters | (unlimited) | ≤ 400m2 per UU |
| Building class 5 | Other buildings, including underground buildings, not special buildings | ≥ 13m ≤ 22 meters | (unlimited) | ≥400m2 per UU |
Building class 1
Free-standing buildings have the lowest hazard potential and therefore the lowest building class 1. This is because the structural fire protection requirements are designed to protect neighboring buildings – where there are no immediate neighboring buildings, fires do not jump over as easily. It is further divided into subcategories a and b:
- Building class 1a is assigned to freestanding buildings that are not higher than seven meters. In addition, these may only have 2 units of use with a maximum total area of 400 m².
- Building class 1b includes detached buildings and buildings used for agriculture and forestry.
Building class 2
For building class 2, the same criteria apply as for class 1a buildings in terms of height and the number and size of use units. In contrast to class 1a, however, they are not free-standing buildings in building class 2, but can also be built together.
Building class 3
Building class 3 includes all other buildings with a height of up to seven meters. They may have more than two units of use and their gross floor area may exceed 400 m². The decisive factor is the height of the building, not its dimensions. Building complexes also pose a low risk if they are lower than seven meters.
Building class 4
In building class 4, the area of the building again plays a role. The utilization units must not be larger than 400 square meters. The actual increase in hazard potential results from the building height of up to 13 meters – in tall buildings, the chimney effect of the tall building can cause fires to spread more quickly.
Building class 5
Building class 5 includes all other buildings (e.g. also underground buildings) with a height of up to 13 meters, whose utilization units can also be larger than 400 square meters. From a height of 22 meters, the regulations for high-rise buildings apply.
Other regulations for building materials and components apply to special buildings.
In which building class does a single-family house belong?
If you look at the classic detached single-family house, it is most likely to be classified as category 1a. However, when classifying it, pay close attention to the actual height and square footage. If the size limits are exceeded, it falls into the size categories 3 to 5.
What role do building classes play in fire protection?
The classification into building classes is decisive for the fire protection regulations. The higher the building class, the higher the requirements for components and building materials. Houses of higher building classes are higher, more complex and are also used by more people than houses of a lower class. Therefore, fire protection is elementary here.
In classes 1 to 3, only “fire-retardant” materials are required for load-bearing components. These must remain load-bearing for 30 minutes in the event of a fire. In building class 4, “highly fire-retardant” building components with a load-bearing capacity of at least 60 minutes are already required. In the highest class 5, “fire-resistant” building components must be installed. These must guarantee a load-bearing capacity of at least 90 minutes.
