Determining Slope Ratio

To determine the slope of your ramp and how much horizontal space it will require, use the following calculation per the ADA guidelines: Multiply the inches your ramp will rise by the slope ratio you desire, and then divide the sum by 12 (to convert the horizontal space you'll need to feet). For example: 31-inch rise x 20 slope ratio = 620. That divided by 12 gives you a 51-foot horizontal projection [source: WheelchairRamp]. ­

Wheelchair Ramp Specifications

­You need to consider your users and­ their limitations when you build a wheelchair ramp. The ramp must be wide enough to be safe, sturdy enough to carry the weight of electric wheelchairs and have a slope that's gentle enough for a manual wheelchair user to navigate. Safety is integral, and many different aspects must be considered.

The Americans with Disabilities Guidelines dictate how ramps are designed for all public places. The guidelines hel­p private homeowners create ramps that are usable, safe and sturdy. The ADA guidelines recommend a slope ratio of 1:16 to 1:20. (A 1:12 ratio is too steep for some people to navigate.) These ratios must be followed in all public places. Homeowners aren't required to follow these slope guidelines; however, if you have the space available, there's really no reason not to [source: Access-board].

ADA guidelines make the following stipulations:

  • Minimum ramp width must be 36 inches.
  • Ramps must have edge protection to keep anyone from slipping off.
  • Ramps must have landings at top and bottom that are as wide as the ramp and at least 60 inches long.
  • Handrails are required on both sides of all ramps that rise steeper than 6 inches or have a horizontal projection of more than 72 inches.
  • Cross slopes must be less than 1:50 and surfaces must be slip-resistant and stable.

Other surface requirements must be met and you will learn about them in more detail in the next section.

Ramps can be constructed from a variety of different materials, though some are better than others. Next, we'll learn which materials are best for what circumstances.