Riser routes cannot be attached to the rear building ground
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 starting point
In a multi-story building, function-maintaining cables must be routed vertically. However, there is no load-bearing wall available in the designated riser zones to which the cable routing system could be attached in accordance with the expert opinion on the standard supporting structure. The distance between the wall and ceiling is 3.3 m, and the opening is 15 × 10 cm. Twelve (N)HXH E30 5×1.5 mm² cables, eight (N)HXH E90 5×2.5 mm² cables, and six JE-H(St)H E30 2×2×0.8 mm cables are to be laid. This results in a typical situation in multi-story buildings where the classic mounting points are not available.
Solution: Suspended installation with fastening adapters
In such cases, suspended mounting of the cable ladder with mounting adapters is recommended. Two mounting adapters are anchored to both the raw ceiling and the raw floor using building authority-approved dowels. The climbing route is screwed firmly to the ceiling, but only guided at the floor (as a slide bearing) in order to accommodate thermal expansion in the event of a fire. A minimum distance of 45 mm must be maintained between the end of the route and the floor to ensure sufficient clearance for the expansion of the side rails.
The width of the route must be selected so that the edge distances of the dowels to the opening are maintained. This ensures that the fastening remains secure and meets the requirements for static and fire protection stability.
Alternative design for large ceiling openings
If the ceiling opening is so large that the fastening adapters cannot be mounted directly on the raw ceiling, a U-profile can be used above and below the opening to bridge the gap. These U-profiles are firmly anchored in the concrete of the raw ceiling and floor using suitable dowels, taking into account the required edge distances. Two threaded rods are then inserted between the profiles, to which the fastening adapters are screwed.
In combination with the ceiling bulkhead, this construction allows load transfer to the fire compartment above, while the lower U-profile remains cold in the event of a fire and therefore does not need to be dimensioned for a load-bearing function.
Structural background and practical recommendations
The application described often occurs when riser zones are planned without load-bearing rear ground, such as in buildings with installation shafts, narrow supply shafts, or in the case of retrofits. Since neither DIN 4102-12 nor MLAR, the Model Building Code (MBO) or the Model Administrative Regulation for Technical Building Regulations (MVV TB) provide specific guidelines on this, planners and installers often have to resort to individual design solutions.
The use of a suspended riser installation ensures functional integrity in accordance with DIN 4102-12, reduces the risk of impermissible deformation, and at the same time ensures mechanically unloaded cable routing. In addition, the solution allows easy adaptation to different ceiling thicknesses or opening sizes without compromising the fire protection classification of the system. It thus offers a tried-and-tested alternative to conventional fastenings.
