Home Improvement Exterior Remodel Roof

Guide to Roof Pitch and Roofing Materials

By
Lee Wallender
Lee Wallender
Lee Wallender

Lee has over two decades of hands-on experience remodeling, fixing, and improving homes, and has been providing home improvement advice for over 13 years.

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Updated on 01/25/24
Reviewed by
Kelly Bacon
Kelly Bacon
Reviewed by Kelly Bacon
Kelly Bacon is a licensed general contractor with over 40 years of experience in construction, home building and remodeling, and commercial building. He is a member of The Spruce Home Improvement Review Board.
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Fact checked by
Emily Estep
Emily Estep
Fact checked by Emily Estep

Emily Estep is a plant biologist and journalist who has worked for a variety of online news and media outlets, writing about and editing topics including environmental science and houseplants.

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Rooftops in suburban development, Colorado Springs, Colorado, United States

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In This Article

Roof pitch matters when choosing roofing materials. Certain materials must stay within a range of roof pitches. MSR rolled roofing, for instance, is best used on low-sloped roofs, such as a 1:12 pitch roof. With most homes, roof pitches typically fall in a range of 4:12 (moderate) up to 8:12 (steep). Learn about roof pitch, how to calculate roof pitch, and which roofing materials work for which roof pitches.

Roof Pitch

Roof pitch is the angle of a roof. Roof pitch is designated by two numbers that indicate a ratio. The numbers can be separated by either a slash or a colon. For example, the pitches 2:12 and 2/12 mean the same thing: the roof rises two feet for every 12 horizontal feet.

Roof Pitches and Roofing Materials

Material Roof Pitch Roof Pitch Type
Built-Up (BUR) 0.25:12 to 3:12 Low
Torch-down roofing 0.25:12 to 3:12 Low 
Rubber membrane 0.25:12 to 3:12 Low
Standing-seam metal 1:12 to 19:12 Low to steep
Asphalt (composite) shingles 4:12 to 20:12 Medium to steep

How to Calculate Roof Pitch From the Roof

To determine roof pitch while standing on a roof, you'll need a bubble level, a 4-foot-long board, and a tape measure.

  1. Place one end of the board on the peak of the roof.
  2. Place the bubble level on top of the board.
  3. Raise or lower the board as needed until you get a level reading.
  4. At the opposite end of the board, use the tape measure to measure vertically from the end of the board to the roof.
  5. Note the measurements and calculate the roof pitch.

Example

The tape measure reads 2 feet. So, for every four horizontal feet, the roof dips 2 feet vertically. The roof pitch is 2:4. To express the same pitch in a more familiar XX:12 format, multiply both numbers by three. So, the roof pitch is 6:12.

How to Calculate Roof Pitch From a Ratio

When you see a roof pitch ratio, the number before the colon (or slash) is vertical feet and the number after the colon is horizontal feet.

For example, the roof pitch ratio 5:12 means that for every 12 horizontal feet, the roof changes 5 feet in vertical height.

Roof Pitches and Roofing Materials

Very Low Roof Pitches: 0.25:12 to 3:12

Roof pitches with lower angles, such as 1:12 up to 3:12 are found in more urban, contemporary-style houses and industrial buildings and shacks.

Modern-style homes built in the 1960s often have little pitch, just a barely negligible slope to help drain water. Visually, this roof appears flat. This pitch might be as low as 1:12. The flat roofing materials most appropriate to these shallow-sloped roofs include:

  • Built-Up Roofing: Sometimes called tar-and-gravel, or BUR, the modern form of this kind of roof consists of alternating layers of bitumen and reinforcing fabrics.
  • Torch-Down Roofing: This is a single-layer membrane-style roofing material that is heat-activated by a torch during installation.
  • Rubber Membrane: EPDM (short for ethylene propylene diene monomer) is a true rubber that can be applied to a roof with glue or mechanical anchors.
  • Standing Seam Metal: These roofs are made from panels of aluminum or steel joined together in raised seams. They can be used on roofs with pitches as low as 0.25 :12. They are also used on much steeper roofs.

Low Roof Pitches: 2.5:12

Clay or cement tiles can be used on a wide range of roof pitches. For pitches of 2.5:12, the roof requires a double underlayment.

Normal or Moderate Roof Pitches: 4:12

Traditional 3-tab shingles made with asphalt composite are the most popular type of shingle and are the most flexible in terms of adapting to many roof pitches.

These shingles are appropriate for pitches as low as 4:12 pitch, all the way up to a 12:12 pitch. Think of them as taking the middle road in terms of roof pitch—not too flat, not too steep.

High Roof Pitches: 5:12 to 12:12

Wood and slate shingles are used in many of the same types of roofs as asphalt composite shingles but may not be appropriate for roofs near the lower end, since they are more susceptible to leaking. Wood and slate shingles do not lock together as tightly as other types of shingles.

Very Steep Roof Pitches: 18:12

Roofs on Victorian-era houses were often sharply angled with a steep pitch. Think of an old house with its soaring peaks and you have a picture of a high-pitched roof. This is one of the rare pitches where the numerator is greater than the denominator, with a slope as high as 18:12.