There is an exhaustive list of panel profiles, materials, coatings and designs available for metal roofing. The most common is standing seam, – a series of flat panels with vertical seams (standing seams) that allow the individual panels to be field connected to each other. The other is exposed fastener (corrugated), which has grown in residential popularity largely to its ease of installation and simplicity in design.
Panel terminations, penetrations and flashing are the main cause of roof leaks, they need to be specifically identified and detailed during the roof design process. There are two different basic designs of metal roofing, hydrokinetic and hydrostatic. We provide design and installation details for both.
Hydrokinetic: Flat Lock / Complanate. A hydrokinetic roof directs the majority of the water over its surface due to kinetic (moving) forces of gravity. This type of roof does not require the seams or ends of the panels to be completely watertight and, therefore, requires the use of an enhanced waterproofing underlayment to completely resist all water intrusion. The metal panel merely provides a cover over the underlayment, much like shingles do. Many manufacturers and associations suggest minimum roof slope of 3:12. This type of metal roof should only be specified when all of the specific conditions have been considered and allowing water under surface in certain areas can be completely handled by underlayment and, therefore, is acceptable.
Hydrostatic: Snap Lock / Corrugated. A hydrostatic roof is designed to keep all of the water on the outside surface. It is designed to handle standing and/or blowing water from entering the interior space for, as long as necessary. The configuration of these panels can vary greatly, but the end result should always be a contiguous metal surface, impervious to water intrusion. This system still requires an appropriate underlayment for backside surface condensation.
A metal roof system when designed with proper specification and professional installation will last as long as or longer than most other building components. The designer’s responsibility is to ensure that these two critical items are specified, and observed for compliance during installation. Make sure that this happens on all metal roof projects to ensure a long lasting, aesthetically pleasing, leak-free roof.