1. What is Flat Roof Slope?

Flat roof slope refers to the slight incline designed into "flat" roofs to ensure proper water drainage. While called "flat," these roofs actually have a minimum slope to prevent water pooling and potential damage.

2. How Does the Calculator Work?

The calculator uses the slope ratio formula:

Where:

• \( rise \) — Vertical change (typically measured in inches)
• \( run \) — Horizontal change (typically measured in feet)

Explanation: The slope ratio represents the vertical rise per unit of horizontal run, typically expressed as a ratio (e.g., 1:48).

3. Importance of Proper Roof Slope

Details: Proper roof slope is crucial for effective water drainage, preventing leaks, ponding water, and structural damage. Building codes typically require a minimum slope for flat roofs.

4. Using the Calculator

Tips: Enter the vertical rise in inches and horizontal run in feet. Both values must be positive numbers. The calculator will provide the slope ratio.

5. Frequently Asked Questions (FAQ)

Q1: What is the minimum slope for a flat roof?
A: Most building codes require a minimum slope of 1/4" per foot (1:48 ratio) for proper drainage.

Q2: How is slope ratio different from slope percentage?
A: Slope ratio expresses the relationship as rise:run (e.g., 1:48), while slope percentage is calculated as (rise/run) × 100%.

Q3: Can I use different units for rise and run?
A: Yes, but the units must be consistent. This calculator uses inches for rise and feet for run, which is standard in roofing.

Q4: What are common slope ratios for different roof types?
A: Flat roofs typically range from 1:48 to 1:24, while pitched roofs have steeper slopes from 4:12 to 12:12 or more.

Q5: How does slope affect roofing material choices?
A: Different roofing materials have minimum slope requirements. Lower slopes require specialized waterproofing systems.