Whether a load-bearing wall must withstand fire for 30, 60 or 90 minutes is not decided by the client's preference but by the building class the house falls into. Structural fire protection fixes wall build-ups, materials and floor plans before the first stone is laid. Plan it late and you pay twice.
Märkische Projekt Bau has been building from Wildau across Berlin and Brandenburg since 1999 and is a certified fire protection specialist company. Masonry firewalls, fire-resistant reinforced concrete floors and timber structures with certified cladding are built by our own bricklayers, concrete workers and carpenters on site, with no subcontractor in between. This article shows which requirements apply and when.
What structural fire protection covers
The field distinguishes four areas: structural, technical, organisational and defensive fire protection. Sprinklers and fire alarm systems belong to the technical side, escape and rescue plans to the organisational side, the fire brigade to the defensive side. Structural fire protection sits in the building itself: in load-bearing components that stay stable long enough in a fire, in walls and floors that stop fire and smoke from spreading, and in escape routes that let people reach safety.
Little of this can be retrofitted. A sprinkler system can be hung into a finished building, a firewall cannot, because it must run in its planned position from the foundation up past the roof. That is why fire protection belongs in the design stage, not in the execution drawings.
The building class sets the requirements
The Brandenburg Building Code (BbgBO) divides buildings into five building classes, and the Berlin Building Code follows the same pattern. What counts is the height of the top floor with habitable rooms above ground level, plus the number and size of the occupancy units. The higher the class, the longer components must resist fire.
| Building class | Typical buildings | Load-bearing components |
|---|---|---|
| Class 1 | detached single-family houses up to 7 m in height | usually no fire resistance requirement |
| Class 2 | semi-detached and terraced houses up to 7 m in height | fire-retardant (F30) |
| Class 3 | other buildings up to 7 m in height | fire-retardant (F30) |
| Class 4 | buildings up to 13 m in height with units up to 400 m² | highly fire-retardant (F60) |
| Class 5 | other buildings up to the 22 m high-rise threshold | fire-resistant (F90) |
| Special building | halls, assembly buildings, care facilities, high-rises | case-by-case requirements, often with a fire safety concept |
The gap between two classes often costs more than the gap between two levels of fit-out. If an added set-back storey pushes a planned building from class 3 into class 4, fire-retardant components become highly fire-retardant ones, and stricter rules apply to the fire protection proof. So settle the class before the design is fixed.
Fire resistance ratings: F30, F60, F90
The number after the F states the minutes a component must survive in the standard fire test: F30 means fire-retardant, F60 highly fire-retardant, F90 fire-resistant. Under the European standard the same levels are called REI 30 to REI 90; R stands for load-bearing capacity, E for integrity, and I for keeping the side facing away from the fire from overheating. Material classes rate the building material itself: masonry, concrete and gypsum boards count as non-combustible, timber as normally flammable. What gets tested, though, is the assembly as a whole, so a component made of combustible material can still achieve a high fire resistance. In practice, clients mostly encounter these measures:
- firewalls of masonry or reinforced concrete between buildings and building sections
- fire-resistant floors and beams, with steel members often clad or coated for fire protection
- fire doors and gates rated T30 to T90 in firewalls and stairwells
- certified penetration seals where cables, pipes and ventilation ducts pass through walls and floors
- required stairwells and corridors that must stay smoke-free as escape routes
Firewalls and fire compartments
Firewalls divide large buildings into compartments so that a fire cannot take hold of the whole house. The BbgBO requires them, among other cases, as a boundary wall near the property line and as internal firewalls at intervals of no more than 40 metres (section 30 BbgBO). In hall construction especially, the layout of the fire compartments shapes the structure, the escape routes and the insurance terms; the other cost drivers there are covered in our article on costs and construction time in hall construction.
The most critical spot of any firewall is the opening. Doors and gates there need an approved, self-closing fire shutter, and every cable tray and every pipe needs a certified penetration seal. Whoever plans the building services only after the shell is finished ends up chiselling openings into finished F90 components and paying for the sealing twice.
Fire protection in timber construction
Timber burns, but it burns predictably. The surface chars at less than one millimetre per minute, and the cross-section behind it keeps carrying load as long as enough material remains. Structural engineers therefore size timber components so that a sufficient residual cross-section is left after the required fire duration.
The second route runs through cladding: gypsum boards protect the timber from igniting for a defined time, 60 minutes in the case of encapsulation class K260. Our carpentry shop builds roof trusses, timber structures and timber-frame walls that reach the required fire resistance rating with the right boarding. How far timber is permitted in building classes 4 and 5 depends on the individual case; clarify this early with your fire safety planner and the building authority.
The fire protection proof in the building application
No building application goes through without a fire protection proof. For buildings in classes 1 to 3 the design author may usually prepare it; for classes 4 and 5 and for special buildings, section 66 of the BbgBO sets higher requirements for who prepares and who checks it. How the application runs as a whole and how long the building authority takes is covered in our article on the building application in Brandenburg.
Special buildings are buildings with an increased risk, such as assembly buildings, larger retail premises or many commercial halls. There, a fire safety concept often takes the place of the simple proof, and the authority can impose conditions, from a fire alarm system to a fire brigade access road. For the new combined heat and power plant on the Funkerberg in Königs Wusterhausen we handled the turnkey construction without the power plant technology; in technical structures like these, building design, plant engineering and fire protection interlock from day one.
Fire protection in existing buildings: renovation and conversion
In existing buildings the first question is: what was actually built? Old drawings are missing or no longer match, and earlier conversions have drilled through floors and damaged penetration seals. Every design therefore starts with a survey of the existing structure; how that works in practice is shown in our article on gutting and renovating old buildings.
For the Berliner Werkstätten für Menschen mit Behinderung we are building two extensions, gutting the existing building and adapting the floor plans. New floor plans mean new escape routes. And new escape routes mean new requirements for walls, doors and floors, which we coordinate with the fire safety planner component by component.
Two cases demand extra coordination. In the listed tram depot in Alt-Heiligensee we built new masonry walls and installed reinforced concrete floors; there, every fire protection measure must also pass the heritage authority. And where the house stays occupied during the works, as with the extension for Märkische Heimat in Ludwigsfelde, the escape routes must stay clear in every construction phase; how we organise that is described in our article on conversions during ongoing operations.
What makes fire protection expensive
It is rarely the single fire door. Fire protection gets expensive when requirements surface late, when the building's classification changes, or when an already checked proof has to be reopened. We see five drivers again and again:
- a jump in building class, for instance through an additional storey or a larger occupancy unit
- classification as a special building with a fire safety concept and official conditions
- later changes to an already checked fire protection proof
- surprises in the existing structure, from missing penetration seals to floors with no provable fire resistance
- building services planned only after the shell, whose openings then have to be sealed retroactively
The best defence is the right order: first settle use and building class, then design, then build. As a company with its own trades we coordinate shell construction, carpentry and fit-out so that fire protection details do not get lost between subcontractors. What we take on is listed under services.
Your next step
If you are planning a new build, an extension or a conversion, we first clarify use, building class and the route to the fire protection proof with you. Märkische Projekt Bau has been planning and building in Berlin and Brandenburg since 1999, within around 50 km of Wildau, as a certified fire protection specialist company with its own bricklayers, concrete workers and carpenters. You can reach us at +49 3375 95 09 70 or through our contact form.
