It is our opinion that in high wind zones, a clip system would be preferred over a nail flange system That being said, certain clip systems definitely perform better than others so it is important to know what you are getting and to not assume that a system will be ok just because it has a clip. With a nail flange system you are counting on the head of the fastener to secure the panel down and while the fastener may stay attached in the substrate, the metal slot may rip or pull away from the fastener. This is especially dependent on the metal gauge the nail flange panel is made of . With a clip system you will usually have a minimum of two fasteners per clip and quite often the clip is made from a much thicker gauge than the panel itself. The fastener in a clip goes through a hole designed for that size fastener in lieu of a slot where there is more play. The clip engages over the male leg of the panel creating a strong connection and these clips can be spaced as close or as far apart as needed to meet the requirements for different areas. In a nail flange system, you are limited to the minimum slot spacing. Furthermore, there is less chance of installing the fastener incorrectly in a clip system (i.e. to tight or loose) and clip systems accommodate thermal movement much better. Lastly, you will see some nail flange systems being glued in the panel seams. Doing this allows these panels to achieve some very high uplift pressures because the panel is literally glued together; this is a fairly new approach. While these panels perform well in testing, there is no long term data that we know of showing the performance 10, 20, 30 years down the road. Since metal is a long term product we prefer to use traditional methods of roof attachments within our systems. Hope this helps! -Thad
When installing some architectural metal details there could be a need to install expansion joints. However with metal roofing, a material and panel should be chosen that allows for adequate thermal expansion to the extent that it is not detrimental to the system. For steel we recommend not “pinning” panels longer than 25’, and for aluminum we recommend not “pinning” panels longer than 15’. This will help minimize fastener failure and draw out. Holes that are elongated are an opportunity for a leak and we do not recommend. Hopefully this answered your question, but if not, feel free to reach out to our Technical Department to talk to someone who is more knowledgeable than me: www.sheffieldmetals.com/Resources/Technical-Department Thanks for the comment! -Thad
