Slope ratio The numerical relationship of vertical rise to horizontal run, used to express the steepness of ramps, walkways, and curb cut flares.
Slope ratio is the fundamental mathematical formula used by code inspectors to verify sidewalk compliance. For instance, an ADA-compliant ramp is limited to a slope ratio of 1:12, which means that for every 1 inch of vertical rise, there must be at least 12 inches of horizontal length. Using incorrect ratios during a sidewalk or driveway installation will fail a DOT inspection and require a complete, costly removal and re-pour of the concrete.
Frequently Asked Questions About Slope ratio
What is a slope ratio?
The relationship of vertical rise to horizontal run, used to express steepness. A 1:12 ratio means one inch of rise per twelve inches of length.
How does it relate to percentage?
1:12 is about 8.33 percent, 1:20 is 5 percent, and 1:50 is 2 percent.
Which ratios matter on sidewalks?
1:12 maximum for ramps, 1:20 for running slope on a pedestrian route, and 1:50 maximum for cross slope.
What happens if the ratio is wrong?
The work can fail inspection and require removal and repouring, since slope cannot be corrected on cured concrete.