How long should the ramp be?

How long does a wheelchair ramp need to be?

At the ADA maximum slope of 1:12, a ramp needs 1 foot of length for every inch of rise. Three steps totaling 24 inches need a 24 ft ramp, plus a 5 ft landing at the top and at the bottom — 34 ft in all.

What is the maximum slope for a ramp?

The 2010 ADA Standards allow at most 1:12 — 1 inch of rise per 12 inches of run, or 8.33%. A gentler 1:16 or 1:20 slope is easier for people pushing themselves and needs more length.

When does a ramp need a landing in the middle?

Each ramp run may rise at most 30 inches. A 36 inch rise at 1:12 is 36 ft of ramp in two runs, with landings at the top, the bottom and between the runs — 51 ft in all. Landings must be at least 60 inches long and as wide as the ramp.

Does a ramp need handrails?

Under the ADA Standards, yes, on both sides, when the ramp rises more than 6 inches. A ramp must also be at least 36 inches wide between the handrails.

Do home ramps have to meet the ADA?

Private homes are not required to follow the ADA Standards, but they are the benchmark for a ramp people can use safely, and local building codes often borrow them. A steeper ramp may be allowed for short rises; ask your building department.

What is the cross slope limit for a ramp?

The 2010 ADA Standards (section 405.3) limit the cross slope, the slope across the width of a ramp run, to 1:48, about 2%. A ramp that tilts sideways is harder to use and can tip a wheelchair.

How the numbers are worked out

The run is the rise multiplied by the slope ratio: at 1:12 each inch of rise takes 12 inches of run. A ramp can rise at most 30 inches between landings, so the number of ramp runs is the rise divided by 30, rounded up, and there is a landing at the bottom, at the top and between each pair of runs. Each landing is at least 60 inches long, so the total length is the run plus 60 inches for every landing. Handrails are required when the rise is more than 6 inches.

Worked examples

A porch 18 inches above the ground needs 216 inches (18 ft) of ramp at 1:12, in 1 run with 2 landings, so 28.0 ft in all. A rise of 30 inches needs 30 ft in a single run, 40.0 ft with landings. A rise of 42 inches exceeds the 30-inch limit, so it takes 2 runs and 3 landings: 42 ft of slope and 57.0 ft overall. A gentler 1:20 slope for the 18-inch rise lengthens the run to 30 ft. A 5-inch rise (does not need handrails) needs 5.0 ft of slope.

Common mistakes

Confusing a 1:12 slope with 12% is common: 1:12 is 1 ÷ 12 = 8.33%. Measuring the rise to the top of the porch decking rather than to the finished surface where the ramp ends can shorten the ramp by an inch or two, and an inch of rise costs a foot of ramp. Leaving out the landings is another: the run alone understates the footprint by five feet for every landing. And a ramp that meets the ADA numbers can still be unsafe without edge protection and a non-slip surface.

Sources: 2010 ADA Standards for Accessible Design, section 405 (Ramps): 405.2 slope, 405.3 cross slope, 405.5 clear width, 405.6 rise, 405.7 landings and 405.8 handrails. Related: stair calculator, deck calculator, concrete steps calculator and slope calculator.