A roof pitch is the ratio of a rise to the span of the roof.
Factors like climate and home design can help determine what roof pitch you'll need.
A pitch of 3:12 is the minimum to disperse snow and rain.
Your home’s roof is probably its most essential element. Not only does it set the tone for your home’s look, but it also protects from all sorts of environmental factors, such as rain, snow, and wind.
And if you’re planning a new roof or considering renovating your existing roof, you’ve probably heard some roofing terms, including “roof pitch.” Below, we give you all the need-to-know information about your roof’s pitch, how to determine it, and the effect it has on your home.
What Is Roof Pitch?
Roof pitch is one of the most commonly used terms in roofing. It expresses the roof's steepness as a ratio of the vertical rise to the run (horizontal span). The higher the rise in the ratio, the steeper the roof.
For example, a roof that rises 6 feet in the span of 12 inches would have a 6:12 pitch. It means that for every 12 inches of the span, the rise will be equal to 6 feet.
A flat roof will have no—or a very slight—pitch. Gable roofs will have a higher pitch ratio of 4:12 to 9:12. For roofs with a steeper slope, the pitch could be up to 18:12 or higher.
Why Is Roof Pitch Important?
Roof pitch is one of the many important components of your roof. A roof pitch helps keep the integrity of a building and safety intact.
Climate is a key factor for roof pitch. The steeper the roof pitch, the quicker it will be to shed rain and snow. Flat roofs can collapse under the weight of heavy snow, so roofs in areas with heavy snowfall need to have a medium pitch. In fact, many states where snowfall and rain downpours are common include minimum pitch levels in their building codes.
While a steep roof can give your home an elegant look, it can be expensive to install and repair. It’s important to know the pitch of your roof to determine the amount of material you need for reroofing, adding solar panels, or remodeling the rafters.
How to Measure a Roof Pitch
As previously mentioned, roof pitch is calculated as the rise over the run of the roof.
The rise is the vertical height of the roof, which is the point from the base to the roof's highest point.
The run is the horizontal distance of the roof’s length, typically from directly below the ridge to the exterior wall.
For example, if a roof is 8 feet high and spreads out from the center covering 12 feet in each direction, the pitch would be 8:12. You can download a free app on your smartphone, or consult a local roofing professional to calculate the pitch of your roof accurately. You should never attempt to get on the roof yourself to measure this.
4 Common Types of Roof Pitch
Now that you understand what a roof pitch is, you’ll notice different pitches on different buildings. Style, environmental factors, and the function of the building will all help determine the appropriate roof pitch. Here are a few different types of roof pitches.
1. Flat Roofs
Flat roofs are common with industrial buildings or houses in arid regions where there is not much rain or snow. It’s important to note that even a flat roof will need a slight pitch to keep water from pooling on top of the structure. It will regularly come with a small pitch of one-quarter:12 to 1:12.
2. Low-Pitch Roof
Low pitch roofs are common on simple sheds or buildings. They are easier to install and safer to walk on during repairs or maintenance. A pitch below 3:12 doesn't shed water. With a pitch between 2:12 and 3:12, you can do a double layer of underlayment or use ice and water shield.
3. Medium-Pitch Roof
The medium pitch usually has a 4:12 to 9:12 slope (or 1:3 to 3:4 when mathematically reduced). Most common roofs have a medium pitch with a slope of 6:12, such as gable roofs and hipped roofs.
Medium-pitched roofs are great for getting rid of snow and rain while allowing professionals to easily inspect and repair them without the need for special equipment or tools.
4. High-Pitch Roof
From A-frame homes to ski chalets, high-pitched roofs start from 9:12. High-pitched roofs may present a chic appearance, but they are more expensive to install and repair since they are non-walkable. Professional roofers will need special equipment and safety measures to install and repair a high-pitch roof.
“Insurance pays a labor premium at 7:12 and it's where contractors start charging more,” says Ami Feller of Feller Roofing. “Generally, the first steep category is 7:12 to 9:12, then a second tier is 10:12 to 12:12, and a third tier is anything over 12:12. Each tier costs more.”