How to Determine Roof Pitch: A Comprehensive Guide

Understanding your roof’s pitch is essential for various reasons, including selecting appropriate roofing materials, ensuring proper drainage, and maintaining the structural integrity of your home. In this guide, we’ll explore what roof pitch is, why it matters, and how you can accurately determine it using different methods.

What Is Roof Pitch?

Roof pitch refers to the steepness or angle of a roof. It’s typically expressed as a ratio of the vertical rise to the horizontal run, often noted as “rise over run.” For example, a 6:12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance. This measurement is crucial for determining the type of roofing materials to use and for ensuring proper water drainage. (InterNACHI, Angi)

Why Is Roof Pitch Important?

Understanding your roof’s pitch is vital for several reasons:

• Material Selection: Certain roofing materials are suitable only for specific pitch ranges. For instance, asphalt shingles are typically used for pitches between 4:12 and 12:12, while slate or tile roofs are better suited for steeper pitches. (The Spruce)
• Water Drainage: Steeper pitches allow water to run off more quickly, reducing the risk of leaks and water damage.
• Structural Integrity: The pitch affects the load-bearing capacity of the roof, influencing its ability to withstand snow, wind, and other environmental factors.
• Aesthetic Appeal: The pitch contributes to the overall architectural style and curb appeal of your home.

Methods to Determine Roof Pitch

1. Measuring from the Roof

This method involves physically accessing the roof to measure the rise over a 12-inch run. You’ll need a level (at least 12 inches long) and a tape measure.(Inch Calculator)

Steps:

1. Safety First: Ensure you have proper safety equipment, including a sturdy ladder and fall protection gear.(The Home Depot)
2. Position the Level: Place the level horizontally against the roof surface.(Carpentry Pro Framer)
3. Measure the Rise: At one end of the level, measure vertically from the roof to the underside of the level.(Anchor Roofing)
4. Calculate the Pitch: The vertical measurement is the rise for a 12-inch run. For example, if the rise is 4 inches, the pitch is 4:12. (Inch Calculator)

2. Measuring from the Attic

If accessing the roof is not feasible, you can measure the pitch from inside the attic.(This Old House)

Steps:

1. Set Up the Level: Place a 12-inch level against the underside of a rafter.(The Home Depot)
2. Measure the Rise: Measure the vertical distance from the 12-inch mark on the level to the rafter.(This Old House)
3. Calculate the Pitch: This vertical measurement represents the rise for a 12-inch run. For example, if the rise is 5 inches, the pitch is 5:12. (Inch Calculator)

3. Using a Speed Square

A speed square can help determine the pitch directly in degrees.(Inch Calculator)

Steps:

1. Position the Speed Square: Place the speed square against the rafter, ensuring the body is flush with the roof surface.(Carpentry Pro Framer)
2. Read the Pitch: The angle indicated on the speed square corresponds to the roof pitch in degrees. For example, a 45° angle indicates a 12:12 pitch.

4. Using a Roof Pitch Calculator

Online tools can simplify the process by calculating the pitch based on your measurements.

Steps:

1. Measure the Rise and Run: Determine the vertical rise and horizontal run of your roof.(InterNACHI)
2. Input the Measurements: Enter these values into a roof pitch calculator.
3. Obtain the Pitch: The calculator will provide the pitch ratio and angle. (Angi)

Understanding Roof Pitch Ratios

Roof pitch ratios are expressed as “rise over run,” indicating how much the roof rises vertically for every 12 inches of horizontal distance. Here’s a breakdown of common pitch ranges and their applications:(Angi)

Pitch Ratio	Description	Common Applications
1:12 – 3:12	Low slope	Commercial buildings, modern homes
4:12 – 6:12	Medium slope	Most residential homes, ranch styles
7:12 – 9:12	Medium-high slope	Colonial, Victorian, Craftsman styles
10:12+	Steep slope	Gothic, Tudor, Alpine chalets

Converting Roof Pitch to Degrees

To convert a roof pitch ratio to degrees, use the following formula:

Degrees = arctan(Rise ÷ Run) × (180/π)(The Home Depot)

For example, for a 6:12 pitch:

Degrees = arctan(6 ÷ 12) × (180/π) ≈ 26.565°(InterNACHI)

This conversion can be useful for architectural planning and when using tools that measure angles in degrees.

Common Roof Pitch Types and Their Applications

• Flat Roofs (0:12 – 2:12): While technically not flat, these roofs have a very low pitch and are common in commercial and industrial buildings.
• Low Slope (3:12 – 4:12):