Installations above suspended ceilings with fire resistance ratings of F30, F60, or F90
The basis for this is DIN 4102-12 and the Model Cable System Guideline (MLAR). The general building inspection test certificates (abP), which prove the usability of tested systems in construction, are decisive in this regard. In practice, however, structural conditions often lead to deviations from these specifications. Since neither DIN 4102-12 nor the MLAR, the Model Building Code (MBO), or the Model Administrative Regulation for Technical Building Regulations (MVV TB) provide specific guidelines in this regard, planners and installers often have to resort to individual design solutions.
Technical initial situation
A general power supply is to be installed above an F90 suspended ceiling. Due to the large volume of cables, a 400 mm wide cable tray is required. The installation can only be attached to a ribbed ceiling. The cable route runs perpendicular to the ribs, and the cable weight is 38 kg/m. The ribbed ceiling also has fire resistance class F90. Drilling zones with a maximum drilling depth of 50 mm and a drilling diameter of 10 mm are available for fastening. The distance between the ribs is 70 cm, and there is an air space of 180 mm between the lower edge of the ribs and the F90 fire protection ceiling.
Recommended solution: Cable routing system with Short-Fix dowels and articulated joints
Due to the shallow drilling depth, we recommend using a building authority-approved dowel with fire protection certification, such as the Short-Fix system. This dowel offers sufficient tensile and transverse load-bearing capacity for 90 minutes of fire exposure and is approved for use with installation systems in accordance with MLAR F30–F90.
The recommended installation system consists of the following components:
· Articulated head plate for load bearing,
· U-profile as a supporting element,
· Cantilever with threaded rod connection,
· Articulated ceiling bracket for attachment to the ribbed ceiling,
· Threaded rod and cable tray for cable support.
This combination enables secure and flexible attachment to the ribbed ceiling without affecting the supporting structure or the suspended ceiling.
Structural conditions and distances
For an installation system in accordance with the following conditions
· Hanging rod length: ≤ 1.0 m
· Fastening distance: ≤ 0.75 m
· Maximum load: ≤ 40 kg/m
· Distance between cable trays and fire protection ceiling: ≥ 90 mm
· Distance between suspension rods or threaded rods and fire protection ceiling: ≥ 20 mm
a negative impact on the fire protection ceiling during a fire exposure of up to 90 minutes can be ruled out.
Structural background and practical recommendations
Installations above suspended ceilings with a defined fire resistance rating are among the most challenging areas in structural fire protection. This is particularly true for ribbed ceilings, where the designated drilling zones and drilling depths make it difficult to select suitable installation systems.
