No homeowner is unfamiliar with the basic concerns when it comes to a roof pitch. Slanted roofs are one of the reasons most people prefer to never be up on their roof to begin with, and outside some aesthetic choices, most homeowners tend, as a result, to think “the less pitch the better”.
This is sound, justifiable reasoning all things said, but there are minimum pitches that different types of roofs can have, without failing, coming apart, or failing to work properly overall. Today, we’re going to look at the different popular roofing materials, and point out their suggested minimum pitches.
Some of these pitches are in a ratio unit, not standard degrees. Don’t let these confuse you, as we’ll soon be talking about the conversion between this industry-specific measurement and more standard mathematical units.
Why Pitch is Important
Roofs are pitched for the purpose of sloughing off water from rain and snow. Assisted by the gutters and downspouts, this prevents water from pooling up on top of the building, which would result in water damage, leaks and other untold problems.
Flat roofs, which of course have no pitch per se, have a special drainage system in place to account for this. The trick is, each material has an ideal minimum pitch, and there are other factors that can affect this as well.
For a metal roof, the minimum pitch is divided by the vertical rise per foot by the horizontal slope. For metal roofs, as a result, the minimal pitch is three in twelve. It’s worth noting with metal, though, that certain manufacturers may specify other conditions, and special types of installations may go up or down on this slope.
For metal, consult the manufacturer documentation, and if it’s not specified, go by this three in twelve guideline.
Slate roofs, which are one of the more water-resistive natural roof types out there, are very popular for their organic, homey look and their diversity. They tend to require a 20-degree slope, but in some cases, can go as low as 15 degrees with more unique roofs. Aim for 20, and consult your contractor and manufacturer regarding the 15-degree case.
Tile roofs are a situation where there’s no general rule of thumb. This is because different consistencies and weights and how they lock together are so diverse, it’s entirely up to the manufacturer to provide guidance here. Heed their specifications.
Asphalt, which is one of the older types of roofing out there, has more of an established science, set by the international building code. This code specifies a minimum slope of 17 degrees (two vertical units to twelve horizontal units).
Like tile, corrugated metal slopes depend on roof profile, and will be specified by the manufacturer depending on the material. Heed their specifications, and consult your contractor for more input.
As we see, it can vary widely from one roof type to another, and it depends on a great many factors unique to a given case. To get input on the slope you need for your roof and your material, fill out our contact form or call us today for a no-obligation consultation!