When considering standing seam roof design it is important to know the difference between astructural panel and an architectural panel. Structural panels are commonly applied to low slope applications over open framing, and architectural panels are normally for steeper slope applications with a solid substrate. Two other terms commonly used to describe structural and architectural panels are hydrostatic and hydrokinetic.
Hydrostatic: – considered "watertight"
– normally referred to as structural
– can be applied to low slope applications below 3:12, and sometimes down to 1/4:12
– have high seams that usually range from 1-1/2" to 3" in height
– do not require a substrate or underlayment
Hydrokinetic: – considered "water-shedding" (not watertight)
– normally referred to as architectural
– must be applied to steeper slope applications of 3:12 or higher
– have low seams that usually range from 1/2" to 1-1/2" in height
– require a solid substrate and underlayment
The panel pictured below is considered a hydrostatic panel. Its seam is 2-3/8" in height and it is considered watertight. Structural panels such as this one are very strong and can withstand very high wind uplift pressures. The relatively tall seam height provides enough strength in the panel to allow it to span open framing members. The seam design, along with the factory applied sealant, also allows the panel system to prevent air and water infiltration, even when subjected to water submersion at very low slopes.
An example of a hydrokinetic standing seam panel is shown below. It has a seam height of approximately 1,” must be installed at slopes of 3:12 or greater, and requires a substrate and underlayment. These panels are not considered to be watertight and are susceptible to leakage if installed at low slopes.
Some panels, such as the one shown below, actually have characteristics of both hydrostatic and hydrokinetic panels. The one shown a sleek seam profile, with a height of approximately 1 1/2” and can be applied to slopes down to 1-1/2:12. It requires a substrate and underlayment; however, once the panel goes above a 3:12 slope, the deck and underlayment is no longer required. This type of panel offers some structural strength but also provides an aesthetically appealing look similar to that of an architectural panel.