Seam Selection Vs. Performance:


If you are considering a metal roofing system for your building, you are probably doing so for the appearance and the long term leak free performance that a metal roof can offer. As with most types of roofing systems, there are tremendous differences between various metal systems that you can choose from. Aesthetics and price are two aspects of the roofing project that you, the owner, can easily judge.

Roof performance, however, is not readily apparent to someone that is not a roofing professional. Aesthetics and price are not an indication of how well a seam style will perform. No single panel design is best for all types of roof designs.

There are a lot of metal systems that, by nature, are not very watertight. A common low performance panel design features a separate snap on cap that snaps onto the panel clip- not to the panel. The panel itself is a simple U shape. A few variations feature a vinyl gasket in the cap in an attempt to improve performance. Test reports, however, show that this type of ribs still leaks in the equivalent of a 25 mile per hour wind….which can occur in almost any rainstorm. The gasket also is much more likely to work its way up and off of the rib.

There are some panels that, by design, are much stronger than others and are capable of being installed over open framing. Others have no structural strength and must be installed over a solid deck.

Ultra Seam, like many manufacturers, offers a variety of panel systems for your use…including snap on cap panels. However, we promote the use of mechanically seamed or continuous snap lock panel seam designs for most roof applications, as they have significantly improved performance levels. The US175LS panel snaps together but the connection is continuous and is panel rib to panel rib- resulting in greatly improved water resistance when compared to the snap on cap style panel.

An even higher resistance to water penetration is obtained with a mechanically seamed panel. Test results for a US150 mechanical seam style panel show air infiltration rates that are about 1/26th the rate of a snap on cap panel and NO leaks at 6 times the test pressure that the snap on cap fails at.

For high end performance the use of sealant in the ribs of the mechanical seamed panel is added. The US200 panel has been tested in accordance with ASTM E2140, which is a standing water test, with no leaks.

Obviously, there is a big difference… one that can mean the difference between a leaky roof and staying dry. Ask questions and choose wisely. Roof slope ( is it almost flat or really steep ), roof assembly, detail requirements, local weather, and aesthetics are all items that need to be considered when choosing the best panel system for your building. Your local Ultra Seam plant will be happy to guide you through the selection process so that you end up with the right panel for your building.