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Slope Formula:
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Roof slope, also known as roof pitch, is the steepness of a roof expressed as a ratio of vertical rise to horizontal run. It's a critical factor in roof design that affects drainage, material selection, and structural requirements.
The calculator uses the slope formula:
Where:
Explanation: The formula calculates how many inches the roof rises for every foot of horizontal run, which is the standard way to express roof pitch in the construction industry.
Details: Proper roof slope ensures effective water drainage, prevents ponding, determines suitable roofing materials, and meets building code requirements. Different slopes are required for different roofing types and climate conditions.
Tips: Enter the vertical rise in inches and horizontal run in feet. Both values must be positive numbers. The calculator will provide the slope in inches per foot and the actual rise per foot measurement.
Q1: What is a typical roof slope for residential buildings?
A: Common residential roof slopes range from 4:12 to 9:12 (4 to 9 inches of rise per foot of run), depending on architectural style and climate.
Q2: How does slope affect roofing material choices?
A: Low slopes (2:12-4:12) require special waterproofing systems, while steeper slopes can use standard shingles. Flat roofs (less than 2:12) need membrane roofing.
Q3: What's the minimum slope for proper drainage?
A: Most building codes require a minimum slope of 1/4:12 (1/4 inch per foot) for adequate water drainage, though 1/2:12 is often recommended.
Q4: How do I convert slope to degrees?
A: Use the formula: degrees = arctan(rise/run). Many online calculators can perform this conversion automatically.
Q5: Why multiply by 12 in the slope formula?
A: Multiplying by 12 converts the ratio to inches per foot, which is the standard industry measurement for roof pitch in the United States.