Resistance Factors That Influence Flat Roof Fastening Design

With regard to resistance, there are four factors which have an influence on the calculation:

 

Supporting Structure Requirements for Roof Fasteners

Firstly, the supporting structure used for the attachment plays a role.

 

Selecting the Correct Fastener and Stress Plate Combination

The selected fastening combination, consisting of a stress plate and a screw, also must be defined.

 

Roof Membrane Performance and Material Strength Data

Information about the roofing membrane used, such as the manufacturer, lengths, description, and material strength, is also necessary for the optimal initial sizing.

 

Why Wind Uplift Test Data Improves Initial Sizing Accuracy

Finally, it is also beneficial if the combination of lengths and fastening elements has already been tested in a wind uplift test, and a design load can be used from the corresponding test report. The performance of an initial sizing without the results of a wind uplift test for the selected combination is possible, although it does not generate optimal results. ​​​​​​

 

National Regulations and Minimum Fastener Requirements

When the initial sizing is performed, first the load influences are evaluated, and the selected fastening combination is established. In addition, national specifications such as the minimum number of fasteners per square meter must be considered. In Germany, the minimum number of fasteners per square metre is two, according to the latest version of the Flat Roof Directive.