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Flat Roof Slope Formula:
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Flat roof pitch refers to the slight slope designed into flat roofs to allow for proper water drainage. Even "flat" roofs have a minimum slope to prevent water pooling and ensure proper drainage.
The calculator uses the slope percentage formula:
Where:
Explanation: This formula calculates the percentage slope by dividing the vertical rise by the horizontal run and multiplying by 100 to get a percentage value.
Details: Proper roof slope is crucial for effective water drainage, preventing leaks, structural damage, and extending the roof's lifespan. Building codes typically require minimum slopes for different roofing materials.
Tips: Measure the vertical rise and horizontal run in meters. Enter both values as positive numbers. The calculator will compute the slope percentage, which indicates how many meters the roof rises per 100 meters of horizontal distance.
Q1: What is the minimum slope for a flat roof?
A: Most building codes require a minimum slope of 1-2% (1-2 cm rise per meter) for proper drainage, though specific requirements vary by location and roofing material.
Q2: Can flat roofs be completely flat?
A: No, truly flat roofs would cause water pooling. All flat roofs have a slight pitch, typically between 1-10 degrees (1.7-17.6% slope).
Q3: How do I measure rise and run accurately?
A: Use a level and measuring tape. Place the level horizontally, measure the vertical distance from the level to the roof surface (rise), and measure the horizontal distance (run).
Q4: What's the difference between slope percentage and slope ratio?
A: Slope percentage expresses the ratio as a percentage (e.g., 2%), while slope ratio expresses it as a fraction (e.g., 1:50, meaning 1 unit rise per 50 units run).
Q5: How does roof slope affect material choice?
A: Different roofing materials have minimum slope requirements. For example, built-up roofs typically require at least 1% slope, while single-ply membranes may work with as little as 0.5% slope in some cases.