An Introduction to Roof Pitches

steep modern roof pitch

There are more roofing materials to choose from than ever before. It may seem like any material is fair game for your home, but unfortunately, that’s not the case. Many factors determine which materials are structural supportable by your roof, like a roof's pitch.

What is roof pitch?

"Pitch" is the term for the slant, slope, or angle of your roof. 

Roof pitch is designated by a ratio—two numbers divided by a slash or a colon, like 5:12 or 5/12. (Read: 5 over 12)

The numerator (first number) refers to the height of the roof. The denominator (second number) refers to the length of the roof.

For example, a roof pitch of 5/12 is a common ratio in many homes. For every 12 inches horizontally, the roof increases 5 inches vertically. 

No matter how it’s expressed, it defines the same thing. Most homeowners have roof pitches in the range of 4/12 to 8/12. However, (nearly) flat roofs may express ¼ /12, and perfect 45-degree angle roofs are 12/12.

When speaking of a roof’s pitch, the denominator will always be 12. That’s because a roof’s pitch is always expressed in height over 12 inches in length.

How do I calculate my roof's pitch?

Calculating the roof’s pitch from the underside of the roof is an accurate method to determine the correct ratio because there’s no roofing material to create an uneven surface.

Grab a level, a tape measure, and a pencil, and head up to the attic.

1. Place a level against the underside of a roof rafter. Adjust the level until the bubble is centered between the lines.
2. Find the 12-inch mark on the level. If your level doesn’t have measurement markings, use a tape measure to indicate the 12-inch mark.
3. Measure the vertical distance from level to rafter by extending your tape measure perpendicular to the level. Find the distance from the 12-inch mark to the underside of the same rafter above it. 
4. The pitch is the vertical distance over the horizontal distance. For example, if you measured 5 inches of height with the tape measure at the 12-inch mark on the level, the pitch is 5:12 or 5/12.
Take your time and measure twice when calculating your roof's pitch. Always exercise caution if you climb on top of your roof to determine its pitch.

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What are some other common roof pitches?

Low-pitched roofs

1960s low pitched roof

Homes built in the 1960s have a very gradual slope, just enough to drain water. These close-to-flat roofs were fashionable in their time period and might be as low as 1/12.

High-pitched roofs

Victorian style roof

Victorian-era houses often had the exact opposite approach compared to architectural choices of the 1960s. These roofs were often sharply angled and steeply pitched. In these rare cases, the numerator is greater than the denominator, sometimes even as high as 18/12.


What pitches are best for various roofing materials?

Built-Up, Torch-Down, and Standing Seam Metal

Contemporary urban homes, industrial buildings, and commercial businesses have roof pitches in lower ranges, such as 1/12 to 3/12. Roofs with such gradual slopes are constricted to built-up, torch-down, or standing seam metal roofing materials.

Conventional composite shingles don’t allow water to drain fast enough from low-pitched roofs and are not advisable for these properties.

Asphalt and Composite

Asphalt and composite shingles are ideal for roofs in the 4/12 to the 12/12 pitch ratio. They are the two most common roofing materials, and they are the most serviceable type of shingle material when it comes to roof pitch.

Wood Shake and Slate

Shake and slate shingles are great for roof pitches in the 5/12 to 12/12 ratio. They perform well in the same pitch gap as asphalt and compositions shingles but are more prone to leaks because they don’t lock together as tightly.

These designations are by no means exclusive and do not cover all the available roofing materials for home and business owners. For instance, slate could be used for a lower pitched roof, and standing seam metal may be well suited for a moderately sloped roof. 

How do I hire the best contractor for my roof?

roofer hammering nail on roof

Consult an experienced roofing contractor if you wish to install a more unconventional material on a low or high pitched roof.

Hometown Roofing Contractors can help you identify the best roofing contractor for your next installation. You can consult multiple contractors, determine the best quotes, and see what other customers have to say. 

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