Fastening technique for composite panels (part I)

Composite panels also contribute to reducing construction costs owing to their simple and cost-effective assembly.

The fastening technique forms an integral part of the assembly. The fastening device must absorb the forces exerted by its own weight, snow, wind and temperature loading and discharge into the sub construction. The fastening device and the composite panels are currently not subject to any norm, which is why a General Building Supervision Permit issued by the DIBT (German Institute of Structural Engineering) in Berlin is mandatory. For this reason, only approved screws may be used to fasten the composite panels.

All approved fasteners are made from stainless-steel material no. 1.4301. A stainless-steel washer with a vulcanised EPDM seal must also be used.

Thread-forming fasteners or drill screws are provided for the assembly.

Thread-forming screws

Thread-forming screws form their own female thread when screwed into the sub construction. The composite panels and the sub construction must be pre-drilled for this.

Depending on the sub construction, a distinction must be made between screws with thread form A (coarse thread) and thread form B (fine thread).

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Thread form A for thin walled steel and wood sub construction: Fixing devices with a diameter of 6,5 mm are suitable for composite panels with thin walled steel sub construction (from 1,0 mm to 3,0 mm) and also for wood sub construction. Attention should be paid that the pre-drilling diameter is corresponding with the data of the approval. For wood sub construction the minimum dept of the screw is 50 mm and this has to be pre-drilled, according DIN 1052 - part 2, with a diameter of 4,8 mm.

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Thread form B For steel sub constructions: Fastening devices with a diameter of 6.3 mm are suitable for steel sub constructions from 1.25 mm to 6.0 mm and >6.0 mm. The spiral-shaped circulating notches in the thread reduce the screwing-in time in thicker sub constructions. The cylindrical threaded section of the screw must be fully screwed in the case of sub constructions up to 6 mm thick and thicker sub constructions of at least 6 mm. The sub construction must also be pre-drilled. The pre-drill charts must be followed for each sub construction thickness.

Our next article includes information on other fasteners, e.g. drill screws and their uses