Wednesday, July 16, 2025
Cladding

Guide to selection of fastening systems

Liechtenstein-based Hilti says the lack of research on the fire resistance properties of fastening systems prompted it to conduct a series of tests. The test results can be used as a basis when selecting systems for applications such as facades and cladding.

Hilti's stud anchors ... excellent fire resistance.

The subject of "fastening and fire prevention" has not been given full attention until now and no detailed know-how was available. The performance capabilities of fastenings has hitherto been either underestimated or overestimated - for example, the very "conservative" assumptions of DIN 4102.

In view of this, Hilti conducted many tests in co-operation with the Institut fŸr Massivbau und Brandschutz of the Technical University of Brunswick, Germany, which permit a better evaluation to be made of the fire resistance of fasteners.

Test results indicate that:

  • At high temperatures, the base material breaks down. The damaged area increases with the duration of the fire according to the temperature exposure. Setting an anchor deeper, therefore, helps to keep the fastening intact in concrete;

  • Although metal does not burn, its loading capacity decreases with increasing temperature (especially from about 500 deg C upward). This was shown during the fire test, for example, by slipping nuts or breaking anchor rods. Stainless steels retain their strength longer than ordinary steels;

  • As the temperature increases, the loading capacity of the base material and the fastener decreases. The conclusion is that the load must be reduced below the "normal" level, necessary for ordinary steels to achieve the desired fire rating, for example, 90 minutes.

    Fire prevention products for the following basic applications, should be selected based on the above test results.

  • Suspended ceilings;

  • Fire prevention doors;

  • Facades and cladding;

  • Pipe penetrations or pipe suspensions;

  • Air ducts; and

  • Cable trays/runs.

    If specifications call for stud anchors to meet not only stringent requirements for the stability and strength but also the fire prevention measures, Hilti has just the right anchor available.

    Hilti offers two types of fire-rated stud anchors: HSA standard stud anchors and HST safety stud anchors. Both stud anchors can be used where excellent fire resistance is required (for the zinc-plated and stainless version - approved by the IBMB Germany).

    It has now become very easy for consultants and workmen to select just the right stud anchor for their applications. Hilti can provide technical support.

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