Anyone who designs, builds, or operates buildings cannot avoid one question: How do building components behave in the event of a fire, and how long will they hold up? The Rigips F90 fire resistance classification represents one of the most demanding—and at the same time most common—requirements in German building construction. It describes a fire-resistant building structure made of gypsum boards that must maintain its fire-separating and load-bearing functions for at least ninety minutes in the event of a fire. Understanding this classification means understanding fire protection at its structural core.
- What the F90 fire resistance class means and how it is defined by standards
- The role of gypsum boards in structural fire protection and why gypsum is a unique building material
- How Rigips systems for F90 are structurally designed: wall systems, suspended ceilings, and shaft constructions
- Which standards, test procedures, and approvals are relevant for Rigips F90 fire protection
- How fire-rated panels differ from standard gypsum panels and when to use which type of panel
- Which design details determine the success or failure of an F90 construction
- How Rigips fire protection systems are integrated into the overall design of a building
- What typical errors occur during planning and installation, and how to avoid them
Fire resistance classes: What F90 means and how the classification works
The designation F90 originates from the German standards system and describes a fire resistance class for room-enclosing and load-bearing structural elements. The “F” stands for “fire-resistant,” and the number “90” indicates the minimum duration in minutes during which a structural element must maintain its protective function in a standardized fire test. Specifically, this means: A wall, ceiling, or shaft system classified as F90 must, under the conditions of the standard temperature curve (ETK) according to DIN EN 1363-1, neither ignite on the side facing away from the fire nor collapse nor allow the passage of flames and hot gases for at least ninety minutes.
The European classification system according to DIN EN 13501-2 uses slightly different terminology. Here, building elements are evaluated according to the criteria of load-bearing capacity (R), integrity (E), and thermal insulation (I), supplemented by additional criteria such as mechanical impact (M) or radiation shielding (W). A wall with the European classification REI 90 largely corresponds in its protective effect to the German F90 classification: It must remain load-bearing for ninety minutes, maintain compartment integrity, and limit heat transfer to a defined level. In German construction practice, both classification systems are used side by side, although the building codes of the federal states increasingly refer to the European classes. For Rigips Fire Protection F90, the manufacturer’s system approvals and test certificates always specify which classification applies and under which standard system.
The standard temperature curve used in fire tests is a standardized curve that ideally simulates the temperature progression of a fully developed fire. After ten minutes, temperatures in the test furnace reach approximately 700 degrees Celsius; after thirty minutes, about 840 degrees; and after ninety minutes, over 1,000 degrees Celsius. These conditions are significantly more extreme than many real-world fire scenarios but provide a reproducible and comparable basis for testing. A building component that withstands these conditions for ninety minutes provides, in practice, a reliable safety margin for evacuation, firefighting, and damage mitigation.
Gypsum as a Fire-Resistant Building Material: Physical Principles and Material Properties
Gypsum owes its outstanding suitability for fire protection to a chemical phenomenon: dehydration. Calcium sulfate dihydrate (CaSO₄ · 2H₂O), the main component of gypsum board, contains chemically bound crystalline water. When a gypsum board is heated during a fire, this crystalline water begins to evaporate at temperatures of approximately 100 to 120 degrees Celsius. This process, known as calcination, consumes significant amounts of heat without causing a noticeable increase in temperature on the back of the board. As long as there is still uncalcined gypsum present, the panel acts as a thermal buffer that delays heat transfer to the side facing away from the fire.
This effect explains why gypsum boards occupy a special position in fire protection. Other building materials, such as wood, burn; steel rapidly loses its load-bearing capacity at around 500 degrees Celsius; and concrete can fail due to spalling when heated rapidly. Gypsum, on the other hand, reacts chemically to the heat, releasing water vapor that inhibits the spread of temperature. Only when all of the crystalline water has been consumed does the panel lose its protective effect and begin to disintegrate. For Rigips Fire Protection F90, this means: The structure must be designed so that this depletion process does not occur before the ninety minutes have elapsed.
Fire-rated panels, such as those used in F90 systems, differ from standard gypsum panels in their modified composition. They typically contain glass fibers embedded in the gypsum matrix. These fibers prevent the board from disintegrating abruptly after calcination and hold the weakened material together for some time. This ensures that the board’s fire-compartmentalizing function is maintained even at a stage when the gypsum has already been largely chemically transformed. In its product line, Rigips refers to such panels as fire-rated panels; they are recognizable by the red color of the cardboard surface, which is internationally established as a marker for enhanced fire protection.
Panel Types and Their Suitability for F90 Constructions
Not every gypsum board is suitable for F90 constructions. While standard boards conforming to DIN EN 520 (now largely superseded by DIN EN 15283 and related standards) do offer a certain level of fire protection, they are not sufficient on their own to meet the F90 classification. For this performance level, special fire-resistant panels are used that are classified according to DIN EN 15283-1 or, in the case of gypsum fiber panels, according to DIN EN 15283-2. Gypsum fiber boards, in which fibers are homogeneously distributed throughout the entire board thickness, offer even higher residual cohesion after calcination compared to cardboard-faced gypsum boards. In practice, multi-layer panel constructions are frequently used for F90 systems, where the total thickness and the sequence of layers have a decisive influence on fire behavior.
Structural Systems for Rigips F90 Fire Protection: Walls, Ceilings, and Shafts
Rigips Fire Protection F90 is implemented in practice through various system designs, each of which has been developed and tested for specific applications. The most important categories are non-load-bearing partition walls, cladding for load-bearing steel structures, suspended ceilings, and service shafts. Each of these categories follows its own structural logic, which is validated by system approvals and general building authority test certificates.
Non-load-bearing partition walls in the F90 configuration typically consist of a metal stud frame made of galvanized steel profiles, clad on both sides with multiple layers of fire-rated panels. The studs themselves do not bear any loads from the building, but must remain sufficiently dimensionally stable in the event of a fire so that the panel cladding can maintain its protective function. The wall height, stud spacing, panel thickness, number of panel layers, and fasteners are precisely specified in the system approvals. A typical F90 wall system can consist of two or three layers of fire-resistant panels on each side, depending on the manufacturer and system variant, with panel thicknesses ranging from twelve to fifteen millimeters per layer. The total thickness of such walls is often between 100 and 200 millimeters, depending on the selected stud width.
Cladding for load-bearing steel structures constitutes a separate category. Steel columns and beams rapidly lose their load-bearing capacity in the event of a fire because steel is a good conductor of heat and its yield strength drops sharply as the temperature rises. A gypsum board cladding encases the steel profile and delays the rise in temperature within the steel to such an extent that the load-bearing capacity is maintained for the required duration. For F90, such cladding must be designed so that the critical steel temperature of approximately 500 to 550 degrees Celsius is not reached within ninety minutes. The cladding is not attached directly to the steel itself but is supported by a substructure system capable of accommodating the thermal expansion of the steel.
Suspended ceilings in the F90 configuration protect the ceiling structure above and the cavity containing building services from fire exposure from below. They are particularly common in office buildings, schools, and hospitals, where reinforced concrete ceilings or wooden beam ceilings are protected by a suspended fire-resistant ceiling. The hangers, support profiles, and panel connections must be designed so that the ceiling does not collapse even under one-sided thermal loading. Service openings, recessed lighting fixtures, and access panels are critical points that must be addressed in the system certification and require special care during installation.
Shaft structures for utility runs, elevators, or installation runs in F90 design constitute another important application group. Here, the shaft enclosure is constructed from metal stud framing and fire-rated panels in such a way as to prevent fire spread between floors. Particularly critical are the penetrations of the shaft walls by pipes, cables, and ventilation ducts: Each opening must be fitted with approved fire-rated collars, fire dampers, or compartmentalization systems that do not compromise the F90 classification of the shaft wall.
Overview of Standards, Approvals, and Test Procedures
The regulatory framework for Rigips Fire Protection F90 is multifaceted. At the European level, DIN EN 1363-1 specifies the basic test procedure for the fire resistance of building components. Classification is carried out in accordance with DIN EN 13501-2. Product standards for gypsum boards are established in the DIN EN 520 series (gypsum boards), DIN EN 15283-1 (fiber-reinforced gypsum boards), and DIN EN 15283-2 (gypsum fiber boards). At the national level, the building codes of the federal states play a decisive role, as they specify the structural fire protection requirements for various building classes and types of use.
For practical application, the manufacturer’s system-specific approvals are of central importance. Rigips, a brand of the Saint-Gobain Group, holds general building authority approvals (abZ) from the German Institute for Building Technology (DIBt) as well as European Technical Assessments (ETA) for its fire protection systems. These documents specify exactly for each system product which panel types, panel thicknesses, stud spacings, fasteners, and installation details are permitted in order to achieve the specified fire resistance class. Any deviation from these specifications—even if it appears structurally sound—invalidates the approval and thereby the legal certainty of the structure.
The testing procedure itself takes place in accredited fire testing laboratories. A test specimen of actual or representative size is exposed on one side to the standard fire according to the unit temperature curve, while temperatures are measured, deformations are observed, and the occurrence of flames or hot gases is monitored on the side away from the fire. Strictly speaking, the test result applies only to the tested configuration. However, classification rules and extrapolation methods specified in the standards allow conclusions to be drawn about similar configurations, which forms the basis for system-specific approvals.
Design Details: Where F90 Structures Can Fail in Practice
Even the most meticulous planning of an F90 design is of little use if the installation neglects details that are critical in the event of a fire. Among the most common weaknesses are inadequately sealed connections to exposed ceilings and floors, missing or incorrectly placed fire-rated collars on pipe penetrations, and fasteners that do not comply with system requirements. Every joint, every seam, and every connection is a potential weak point through which flames, hot gases, or heat can reach the protected side in the event of a fire.
The connection of an F90 partition wall to the exposed ceiling is a particularly critical point. The wall must be connected to the ceiling in such a way that neither heat nor smoke gases can penetrate through the gap between the top of the wall and the underside of the ceiling. At the same time, the connection must be able to accommodate the deformations caused by thermal expansion and deflection of the ceiling in the event of a fire. System approvals often specify the use of mineral wool strips, fire-resistant adhesive tapes, or joint sealants that fulfill precisely this function. Anyone who treats these details as trivial and seals them with standard acrylic risks the failure of the entire structure.
Electrical installations are another source of construction errors. Switch boxes, outlet receptacles, and cable conduits in F90 walls must either be installed in a system-compliant manner or secured with appropriate fire protection measures. Installation boxes located directly opposite each other on either side of a partition wall are generally not permitted because they reduce the wall thickness locally to such an extent that the fire protection function is no longer guaranteed. System approvals specify the minimum distances that must be maintained between opposing installation openings and which boxes are approved.
Retrofit modifications to existing F90 structures are a frequently underestimated problem. If new conduits are routed through an F90 wall after a building has been completed, the penetration must be sealed with approved fire-sealing systems. In practice, such retrofit work is often carried out without knowledge of the original system approval, which effectively nullifies the wall’s fire resistance rating. Building operators and facility management personnel should therefore maintain documentation of all F90 constructions in the building and have any modifications performed only by qualified specialist contractors.
Integration into Fire Protection Planning: Rigips F90 as Part of the Overall Concept
Rigips F90 fire protection is not a standalone product, but rather an element within a comprehensive fire protection concept. This concept encompasses structural fire protection (fire resistance of building components, fire compartments, escape and rescue routes), technical fire protection (sprinkler systems, fire alarm systems, smoke exhaust systems), and organizational fire protection (fire safety regulations, fire department access routes, training). The F90 classification of partition walls and ceilings is one of the basic requirements for creating fire compartments that limit the spread of a fire to defined areas.
State building codes specify, depending on the building class and use, which fire resistance ratings are required for which building components. Buildings in Building Class 5—that is, buildings with more than five stories or special uses—are generally subject to the strictest requirements, which often mandate F90 for load-bearing and bracing components as well as for partition walls between occupancy units. Special-purpose buildings such as hospitals, schools, places of assembly, and high-rises are also subject to their own special building codes, which may impose specific requirements that go beyond the general state building codes.
Collaboration between architects, structural engineers, fire protection engineers, and the drywall contractor is essential for the success of an F90 construction project. The fire protection engineer specifies in the fire protection plan which fire resistance classes are required where. The architect integrates these requirements into the detailed design and selects suitable system products. The contractor must be familiar with and comply with the system approvals and must document the installation. Only when all parties involved understand and uphold this chain of responsibility can legal certainty and the actual protective effectiveness of the construction be guaranteed.
Fire Protection as a Structural Responsibility
Rigips Fire Protection F90 is far more than a product designation or a mere compliance requirement. It is an expression of the structural responsibility that architects, planners, and contractors bear toward a building’s occupants. Ninety minutes of fire resistance means time in an emergency: time to evacuate people, time for the fire department to locate and fight the fire, and time to limit the damage. This time is not abstract; it is the result of precise materials science, careful standard-setting, and meticulous craftsmanship in execution.
In this context, gypsum board has proven itself to be a building material that elegantly meets the physical requirements of fire protection: It is lightweight, quick to install, easy to combine with other materials, and, in the event of a fire, releases exactly what is needed for the protective function through its chemical reaction. The systems from Rigips and comparable manufacturers offer a wide range of tested and approved solutions that enable an F90-compliant construction for virtually every application. The key is to ensure that these systems are not misunderstood as a modular system in which any parts can be combined at will, but rather as a tested, integrated whole whose effectiveness depends on compliance with all system specifications.
Anyone who plans and installs Rigips F90 fire protection is undertaking a task that requires technical knowledge, meticulous adherence to standards, and precision craftsmanship in equal measure. The classification is not an end in itself, but rather a promise of protective performance that must be fulfilled in the event of a fire. Fulfilling this promise is the true purpose of structural fire protection.
