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ADA Ramp and Curb Ramp Calculator

Ramp Length Formula

1. What is an ADA Ramp and Curb Ramp Calculator?

Definition: This calculator determines the design parameters for ramps and curb ramps to comply with the Americans with Disabilities Act (ADA) standards, using inputs like vertical rise and available space.

Purpose: It ensures ramps are accessible for individuals with disabilities, meeting requirements for slope, length, landings, and other features.

2. How Does the Calculator Work?

The calculator uses the following key formula:

\( \text{Ramp Length} = \frac{\text{Vertical Rise}}{\text{Maximum Slope}} \)

Where:

  • \( \text{Vertical Rise} \): Height to be overcome (inches).
  • \( \text{Maximum Slope} \):
    • New construction: 1:12 (0.0833).
    • Existing sites: 1:10 (0.1) for rise ≤6 inches, 1:8 (0.125) for rise ≤3 inches.

Steps:

  • Input vertical rise, available space, construction type, and direction change.
  • Validate: Rise and space positive, rise ≤30 inches.
  • Determine maximum slope based on construction type and rise.
  • Calculate required ramp length using the formula.
  • Assess landing dimensions (60” length, 36” or 60” width if direction change).
  • Check edge protection (required if rise >0) and handrails (required if rise >6” or length >72”).
  • Verify if required length fits within available space.
  • Display results in a table.

3. Importance of ADA Ramp Calculations

These calculations are critical for:

  • Accessibility: Ensuring safe and usable ramps for wheelchair users and others.
  • Compliance: Meeting legal ADA requirements for public and private facilities.
  • Design Planning: Guiding architects and engineers in ramp construction.

4. Using the Calculator

Example (Rise = 12 inches, Available Space = 200 inches, New Construction, No Direction Change):

  • Maximum Slope: 1:12 (8.33%) for new construction.
  • Required Ramp Length: \( \frac{12}{1/12} = 12 \times 12 = 144 \) inches (12 feet).
  • Minimum Clear Width: 36 inches.
  • Landing Dimensions: 60 inches (length) x 36 inches (width).
  • Edge Protection: Yes (min 2-inch curb).
  • Handrails: Yes (since rise >6 inches).
  • Space Check: 144 inches < 200 inches, so the design fits.

Curb Ramp Notes:

  • Counter slope of adjoining gutters/roads must be ≤1:20 (5%).
  • Side flare slopes ≤1:10 (10%) for new construction, ≤1:12 (8.33%) for alterations with limited space.
  • Detectable warnings required for transit facilities or FHWA-funded projects.

5. Frequently Asked Questions (FAQ)

Q: What if the required length exceeds available space?
A: For new construction, consider multiple runs or a platform lift. For existing sites, steeper slopes may be allowed if rise is ≤6 inches.

Q: When are handrails required?
A: Handrails are required if the rise exceeds 6 inches or the ramp length exceeds 72 inches.

Q: What is the minimum clear width?
A: The minimum clear width is 36 inches for all ramps.

Reference
https://www.access-board.gov/ada/guides/chapter-4-ramps-and-curb-ramps/

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