A water-shedding, or hydro-kinetic roof, also known as an architectural roof, relies on a steep slope to shed rainwater immediately. These roofs typically incorporate the water-shedding capabilities in the architectural design of the roof itself, which gives rise to the term used to describe them. This roof is ideal for buildings where aesthetics are important, because the inbuilt water resistance is less obvious and just as secure.
Water-shedding roofs need an optimum gradient of at least 3:12 to begin with, which allows the water to run off down to the downspouts and drainage system. Dramatic visual effects are created using low profile standing seam panels with little to no exposed fasteners. The structural design of this style of metal roof is particularly important to provide adequate support for the shape and load of the roof, and installation usually includes an underlayment such as a 30-lb roofing felt or an adhesive-backed ice and water shield.
This article appears at the website of Whirlwind Steel:
How can MBCI claim in court that their roof to be water-shedding only but state on their website that the minimum slope is 1/4:12. Is MBCI right and everyone else wrong? Every where I read, a water shedding roof is to be installed on a minimum 3:12 slope. The right people have not seen this information yet.