Roof Pitch: Everything You Need to Know


Roof pitch is one of the most important aspects of a modern roofing system. Certain components, such as roofing materials and gutter sizing, are affected by it. In this blog, roofing services contractor Achten’s Quality Roofing discusses everything you should know about roof pitch.

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How to Calculate Roof Pitch

Roof pitch is typically represented as a fraction, though it can also be represented as a ratio. Let’s take a common residential roofing slope, 4/12 (or 4:12). The number 4 represents the “rise,” the vertical measure, represented in inches. The second number represents the “run”, or the vertical measure. The run is always represented as 12 inches, or exactly one foot. Therefore, a 4/12 slope means “4 inches of rise for every foot of run.”

To calculate the roof pitch, look for a horizontal beam that’s perpendicular to the roof edge. Using a tape measure, measure 12 inches on it and mark both ends. Measure the vertical distance from one mark to the corresponding rafter, then do the same for the other. Subtract the difference between the two, and you should now have the rise; add /12 and you have the roof pitch.

Aspects Affected by Roof Pitch

  • Efficiency — The steeper the roof, the more efficient it is at shedding rain, snow and all manner of debris. Steep roofs tend to require roof cleaning more at the edges than at the top. The increased efficiency also means proper gutter sizing is critical. Steep roofs will require gutters that can handle high amounts of rainwater.

  • Wind Resistance — Steep roofs are hit by high winds head-on, while gently pitched roofs allow wind to pass over it. Homes in areas that are in the path of high winds should ideally have the latter.

  • Materials — No roof is truly flat. Even commercial “flat” roofing has a slight pitch between 0.5/12 to 2/12. The pitch may be imperceptible, but it is enough to ensure proper roofing drainage. Roof pitch dictates the choice of materials. Some may find this limiting, but given the variety of roofing materials available, the roof pitch can help narrow down your choices.

  • Curb Appeal — Steep roofs are more visible from the curb, which makes them perfect for showing off a beautiful roof.

Achten’s Quality Roofing is the roofing company to turn to for all your roofing needs, including moss cleaning from thr roof. Give us a call at (253) 539-7663 or fill out our contact form to schedule an appointment.