Wheelchair ramp glossary

Rise is the vertical distance from the lower surface to the upper one — grade to threshold, typically. Run is the horizontal length of ramp. Slope ratio expresses their relationship: 1:12 means one unit of rise per twelve of run, and that is the ADA maximum under §405.2. A single run may not rise more than 30 inches under §405.6, which is what forces landings on tall entries.

Cross slope is the tilt across the width of the ramp, capped at 1:48 under §405.3. It's the specification most often violated accidentally, usually in an attempt to drain water, and it's the one that makes a chair drift sideways. Clear width is the usable width — at least 36 inches under §405.5, measured between the handrails where handrails are provided, not deck edge to deck edge.

Landing is a level platform. Required at the top and bottom of every run under §405.7, and at least 60 inches clear wide by 60 inches clear long where the ramp changes direction. Switchback is a layout where the ramp doubles back on itself, joined by that 60-by-60 landing — the standard solution when a straight run won't fit.

Edge protection under §405.9 is what stops a wheel leaving the ramp: a curb at least 4 inches high, a rail configured so a 4-inch sphere cannot pass, or an extended surface reaching at least 12 inches beyond the inside face of the handrail. Handrail extension refers to handrail continuing past the end of the ramp run; handrails are required on both sides where the rise exceeds 6 inches under §405.8. Threshold ramp, portable ramp, modular ramp and permanent ramp are product categories, priced at roughly $50–$500, $100–$1,500, $1,500–$4,000 and $2,000–$5,500 respectively.

How to choose

Learn rise, run and slope ratio first

Those three terms let you check any quote's honesty in one calculation.

Never confuse deck width with clear width

§405.5's 36 inches is measured between handrails. Handrails mounted inboard eat into it.

Treat cross slope as a real spec

1:48 is easy to miss and impossible to ignore once you're in a chair.

Say "60 by 60" out loud when discussing switchbacks

It's the number that determines whether a switchback fits your yard.

Ask which edge protection method is being used

Curb, rail or extended surface — all three are acceptable under §405.9, but one of them has to be there.