What is the correct way to measure the slope of a roof?

The correct method for measuring the slope of a roof is to use a level and measure the rise over a specific run. This approach involves placing a level horizontally on the roof and determining how much the roof rises vertically over a measured horizontal distance. This calculation enables precise determination of the slope, expressed as a ratio or percent, which is essential for assessing drainage and overall roof performance.

Using a level provides accurate and consistent readings, allowing for effective comparisons across different sections of the roof. This method is favored in roofing practices for its reliability and the straightforward nature of calculating the slope, making it an essential technique for roof inspections and installations.

Other methods, like using a ruler and plumb line or digital inclinometer, might yield useful data but may not be as universally applicable or straightforward as measuring rise over run. Visual inspection alone lacks the precision needed to determine actual slope values, which can lead to misjudgments in roofing work.