The slope of a roof has an effect on the interior volume of a home, the drainage, and the style and material used for covering a building. It is also considered to be a primary factor in roof design. Roofs are classified as either steep slope or low slope. Most residential roofs in the U.S. are steep slope, which means the roof is angled on both sides and allows snow, rain and debris to run off it quickly. Typically residential roofs have a slope of 3:12 or greater.
Do you remember learning about “rise over run” in school? Believe it or not, that equation directly applies to the slope of your roof - I bet you never thought you would use that in the “real world,” right? In roofing, the “rise” is the vertical height of the roof from the lowest edge of the roof to the highest point, known as the ridge. “Run” refers to the measurement from the outside of the eave to the point below the center of the ridge. So, a roof with the standard slope of 3:12 means for every 12 horizontal inches (run), the roof has a rise of three or more vertical inches. The slope of a roof is expressed as inches per foot and is written in a ratio format.
Steep-slope roofs generally last longer than low-slope roofs because they shed water efficiently, meaning there is less chance of water damage or leaks. These roofs are susceptible to wind damage though since the wind can go underneath the shingles and weaken or break the connection to the rest of the roof. Overall, steep-slope roofs have relatively low maintenance.
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