How the Number of Flat Roof Fasteners Is Determined

Regarding the number of fasteners to be used, the statements in the rules and regulations are, to an extent, not entirely uniform. The number of fasteners must be determined individually for the different areas of the roof surface, considering the wind loads in accordance with DIN EN 1991-1-4 and DIN EN 1991-1-4/NA.

Technical Requirements for Flat Roof Fastener Materials

Also, with regard to the type of fasteners, there is diverse information in the different regulations about the material of the fastening element. 

Previous K1 and K2 Corrosion Classifications in DIN 18531

Until July 2025, DIN 18531 divided the roof structure into application classes K1 and K2, requiring a corrosion-resistant fastener for the higher-grade roof structure K2. In the current version, the application classes K1 and K2 no longer exist; now only adequate corrosion protection for the fasteners is generally required. 

Corrosion Resistance Requirements Under DIN 18336

DIN 18336 belongs to VOB Part C. VOB Part C covers the general technical contract conditions for building services which must be agreed by the client and contractor. Overall, VOB Part C includes numerous individual standards. In its latest version dated September 2019, point 3.2.1.8 of DIN 18336 states that only corrosion-resistant fasteners are to be used as mechanical fasteners.