To measure the slope on a roof, you determine how many inches the roof rises vertically for every 12 inches it extends horizontally. This measurement is commonly known as roof pitch.
Roof slope, or pitch, is a critical measurement that dictates the steepness of your roof. It's expressed as a ratio of "rise" over "run," where the rise is the vertical height the roof gains, and the run is the horizontal distance it covers.
The Calculation Method
As per standard practice, calculating roof slope involves:
- Calculating the number of inches your roof slope rises vertically for every 12 inches it extends horizontally.
For instance, if your roof rises 7 inches for every 12 inches of horizontal run, then your roof has a 7-in-12 pitch. This means for every foot of horizontal travel across the roof, it gains 7 inches in height.
Practical Steps to Measure Roof Slope
You can measure roof slope relatively simply using a few basic tools. Always prioritize safety when working on a roof or ladder.
Tools You'll Need
- Tape Measure: A standard retractable tape measure.
- Spirit Level (or Builder's Level): At least a 2-foot level is ideal, but a longer one can provide more accurate results.
- Pencil or Marker: For marking.
- Safety Gear: Gloves, non-slip footwear, and potentially a safety harness, especially for steep roofs.
Measuring Procedure
Here's a step-by-step guide to measuring your roof's pitch:
- Access the Roof Safely: Use a sturdy ladder to safely reach the edge of your roof. For accurate measurements, it's best to be directly on the roof surface, away from any overhangs or gutters.
- Position Your Level:
- Place the end of your spirit level flat against the underside of the roof deck or directly on the roof shingles.
- Ensure the level is perfectly horizontal by watching the bubble in the level's vial. Adjust it until the bubble is centered.
- Mark the 12-inch Point:
- While holding the level perfectly horizontal, measure 12 inches horizontally along the level, starting from the point where it touches the roof.
- Make a clear mark on the underside of the level at this 12-inch point.
- Measure the Vertical Rise:
- From the 12-inch mark on your level, use your tape measure to measure the vertical distance straight down to the roof surface.
- This vertical measurement is your "rise."
- Determine the Pitch:
- The number of inches you measured vertically is the "rise" for a 12-inch "run."
- For example, if your vertical measurement was 5 inches, your roof has a 5-in-12 pitch. If it was 9 inches, it's a 9-in-12 pitch.
Why is Roof Pitch Important?
Understanding your roof's pitch is crucial for several reasons:
- Material Selection: Different roofing materials are suitable for various pitches. For example, some shingles are not recommended for very low-slope roofs, while others are specifically designed for flat or low-pitch applications.
- Water Drainage: A proper pitch ensures effective water runoff, preventing pooling and potential leaks.
- Ventilation: Roof pitch can influence ventilation requirements and strategies.
- Cost and Labor: Steeper roofs often require more specialized equipment, safety measures, and labor, potentially increasing installation costs.
- Aesthetics: The pitch significantly contributes to the overall architectural style and appearance of a building.
By accurately measuring your roof's slope, you gain essential information for maintenance, repairs, and future roofing projects.
