How to Measure Wheelchair Ramp Ground Slope

Table of Contents

ADA Requirements

What you will need

Why is it Important To Measure?

Where to Measure

How to Measure

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Tracy Mikulec

Tracy Mikulec, a seasoned leader in the digital marketing realm, currently serves as the Director of Digital at SixAxis, a pioneering manufacturer of industrial and commercial safety products from renowned brands like SafeRack, ErectaStep, and Upside. With a career spanning over three decades, Tracy has been at the forefront of digital innovation, ecommerce, and technology strategy. Since January 2015, Tracy has been instrumental in shaping the digital landscape at SixAxis, LLC, based in Andrews, South Carolina. His role involves leading digital strategies and overseeing technological advancements for SixAxis and its diverse portfolio of brands.

Dec 19, 2019

Estimated reading time: 5 minutes

ADA Requirements

The Americans with Disabilities Act (ADA) requires wheelchair ramps to have a slope no steeper than 1:12 so that people in wheelchairs can go up and down without assistance. This means that for every inch of rise in the threshold, the wheelchair ramp must be 12 inches (one foot) long. For example, a door threshold height of 25″ requires a 25′ ramp along with a 5’ x 5’ threshold platform. Any threshold that is more than 30″ off the ground requires at least one resting platform in the middle of the ramp to break it up. Why? Because the ADA requires a resting platform for every additional 30′ of the ramp run. Therefore, if the threshold is 32″ high, one resting platform is required; if the threshold is 62″ high, two resting platforms are required.

What you will need

Stakes
String or twine
Hammer
Line level
Tape measure

Handicap Ramp Slope and Length Calculator

Handicap Ramp Slope & Length Calculator

Why is it Important To Measure?

In a perfect world, every construction site would be completely flat, but all site workers know that is not the case. Therefore, ground slope measurements are required to make sure that the slope of the handicap ramp is accurate. If the ground is sloping upwards from the door threshold, the ramp will likely require less ramp material than if the ground is flat or sloping downwards. This typically means that the ramp will be less expensive if the ground is sloping upwards and more expensive if it is sloping downwards.

Diagram 1

The 30″ threshold height correlates to a 30′ ramp because the ground is neither sloping upwards or downwards; it is completely flat.

Diagram 2

On the left side of the building, the ground is sloping upwards, which means that the 30″ threshold will require a ramp that is less than 30′. On the right side of the building, the ground is sloping downwards, which means that the ramp will have to be longer than 30′. It will also require a resting platform in the middle of the ramp that will add an additional cost. A resting platform is required for every additional 30′ of ramp run.

Where to Measure

Slope measurements need to be taken where the wheelchair ramp will sit, so you will first need to figure out the best layout. To determine the best layout:

Measure the height of the door threshold
Determine the required ramp length
- For every inch of rise, a foot of ramp run is needed (i.e. door threshold height = 20”, so ramp run = 20’)
- Make sure to account for the required 5’ x 5’ platform at the door threshold
- Remember, for every additional 30′ of ramp run, an additional 5’ x 5’ resting platform is required
Note any obstacles or space limitations
If there are no obstacles or space limitations, the ramp layout does not matter; choose the preferred layout
If there are obstacles or space limitations, a switchback ramp or L-ramp would be best
If there are two buildings side-by-side, a common platform ramp could be used to maximize space utilization

Once the layout is determined, measure the ground slope every 10′ in the direction(s) that the ramp will travel. To measure an L-ramp, measure from where the threshold platform would sit to where the first platform would sit in increments of 10′. Then measure from the platform down to where the ramp would end. For modular buildings, here is a ramp configuration plan.

How to Measure

Take a measurement from grade to the finished floor at the entrance (FFE (finished floor elevation) = _____ inches)

Hammer a stake in the ground at the entrance door and tie a string to it.

Hammer a second stake in the ground straight out from the building at approximately the location where the threshold platform will end (typically 5’4” away from the building), and tie the string to it from the first stake making sure it is taut.

Place a line level in the center of the string and move the string up or down until the line is level.

Measure the distance from the ground to the string at the first stake (S1 = ______ inches) and measure the distance from the ground to the string on the second stake (S2 = ______ inches)

Calculate the ground level relative to the finished floor elevation (FFE) by using the following formula: FFE_2 = FFE + (S2 – S1)

Hammer a third stake in the ground approximately 10’ from stake 2 in the direction of the ramp travel. Tie a string from stake 2 to stake 3 and make sure that the string is taut.

Place a line level in the center of the string and move the string up or down until the line is level.

Measure the distance from the ground to the string at stake 2 (S2 = ______ inches) and measure the distance from the ground to the string at the third stake (S3 = _____ inches)