ADA Waterfront Access Guide: Ramp and Gangway Slope Rules
Accessible waterfront access comes down to geometry. A ramp from a building or a gangway down to a floating dock has to meet the 2010 ADA Standards for Accessible Design, and the numbers are fixed: slope, rise per run, landings, width, handrails and edge protection. This guide lays out those rules section by section, the way Alummikon checks a ramp or gangway layout before it is designed.
Important: this is code geometry only. It does not size members or check deflection, wind, snow, ice, live load, hinge and roller detailing, flotation or anchorage. Every built project needs review and sign-off by the engineer of record, Sullaway Engineering, on a per-project basis.
The core ramp rules at a glance
| Requirement | Rule | ADA section |
|---|---|---|
| Maximum running slope | 1:12 (8.33%) | 405.2 |
| Maximum cross slope | 1:48 (2.08%) | 405.3 |
| Minimum clear width | 36 in, measured between handrails where handrails are provided | 405.5 |
| Maximum rise per run | 30 in | 405.6 |
| Landings | Top and bottom of every run, at least as wide as the widest run | 405.7, 405.7.2 |
| Landing length | 60 in minimum | 405.7.3 |
| Change-of-direction landing | 60 in by 60 in | 405.7.4 |
| Handrails | Required when rise exceeds 6 in, both sides | 405.8, 505.2 |
| Handrail height | 34 in to 38 in to the gripping surface | 505.4 |
| Handrail extensions | 12 in past the top and bottom | 505.10.1 |
| Edge protection | Surface extends 12 in beyond the rail, or a barrier that stops a 4 in sphere | 405.9 |
Slope: one foot of run for every inch of rise
At the maximum 1:12 running slope, every inch of rise costs a foot of horizontal run. A 30 in rise needs 30 ft of sloped ramp, before you add landings.
A walking surface at 1:20 or flatter is not a ramp, so section 405 does not apply to it, though cross slope is still capped at 1:48 and clear width is still 36 in minimum (403.3, 403.5.1).
There is one narrow exception. In an existing facility where space limitations prohibit 1:12, Table 405.2 allows 1:10 for a rise of 6 in or less, and 1:8 for a rise of 3 in or less. Steeper than 1:8 is prohibited. Whether a site qualifies as space-limited is a professional judgment, not a calculation.
Runs, landings and switchbacks
No single run may rise more than 30 in (405.6). A larger rise is split into multiple runs, and every run gets a landing at the top and bottom (405.7). A 30 in rise sits exactly at the limit, so it is one run with no intermediate landing.
The total footprint of a straight ramp is the sloped run plus a 60 in landing at each end and at each intermediate break. When the site does not have that much length, a ramp with two or more runs can be folded into a switchback. The turn landing must be a clear 60 in by 60 in (405.7.4). A single-run ramp cannot be folded.
If neither a straight nor a switchback layout fits the available run, no compliant ramp fits the site. The options are to reduce the rise, obtain more run, or use a platform lift or elevator.
Width, handrails and edge protection
Clear width is 36 in minimum, and where handrails are provided it is measured between the handrails, not across the frame. A 3 ft nominal frame may not leave 36 in clear once rails are mounted inboard, so the clear dimension has to be confirmed. A 4 ft nominal width leaves margin over the 36 in requirement.
Once a run rises more than 6 in, handrails are required on both sides, with the gripping surface 34 in to 38 in above the ramp and extending 12 in past the top and bottom of the runs.
Every run and landing with a drop-off needs edge protection: either extend the walking surface 12 in beyond the inside face of the handrail (405.9.1), or provide a curb or barrier that stops a 4 in diameter sphere (405.9.2).
Marine gangways: low water governs
A gangway to a floating dock does not have one rise. The float moves with the water. At high water the gangway climbs the least; at low water the rise becomes the high-water rise plus the full tidal or seasonal water level change. Low water always governs, because that is when the gangway is steepest.
To hold a true 1:12 at every water level, gangway length grows as rise multiplied by the square root of 145, divided by 12 (rise in inches, length in feet). Measure the rise at high water and add the full water level change to get the low-water condition. If the rise was measured at low or mean water instead, the slope results will be wrong.
Gangway exceptions for boat slips (ADA 1003.2.1)
Gangways serving boat slips at a recreational boating facility get specific relief under section 1003.2.1:
| Exception | What it does |
|---|---|
| 1003.2.1 EX 2 | Gangways are not held to the 30 in maximum rise per run, so no intermediate landings are triggered. |
| 1003.2.1 EX 3 | At 80 ft minimum total gangway length, the 405.2 slope limit does not apply. |
| 1003.2.1 EX 4 | At a facility with fewer than 25 boat slips, a gangway of 30 ft minimum total length is not required to comply with 405.2. |
| 1003.2.1 EX 5 | Landings at top and bottom are not required where transition plates are used. |
| 1003.2.1 EX 6 | Handrail extensions are waived at transition-plate connections only. |
| 1003.2.1 EX 7 | Cross slope is measured in the static position. |
A gangway that relies on EX 3 or EX 4 is legally compliant, but it will be steeper than 1:12 at low water. That should be put in writing to the owner.
What still binds on every gangway
- Cross slope no steeper than 1:48, measured in the static position.
- Clear width of 36 in minimum, measured between handrails. There is no gangway exception to this.
- Handrails on both sides, gripping surface 34 in to 38 in.
- Edge protection: deck extended 12 in beyond the inside face of the handrail, or a barrier that stops a 4 in sphere.
- Landings top and bottom, unless transition plates are used.
These exceptions apply only to accessible routes serving boat slips. A gangway on a general public waterfront route that does not serve slips gets none of this relief and must hold 1:12 at every water level. Note also that 1003.3.1 is "Boat Slip Clearance" and is not the gangway provision; the relief is at 1003.2.1.
When no gangway length that fits the site holds a compliant route across the full water range, the fix is geometry: lower the fixed landing, raise the float freeboard, add an intermediate float to split the rise, or provide a second means of access.
Alummikon gangway widths
Alummikon commercial gangways come in two widths, configured per foot of length: #866 at 3 ft wide and #867 at 4 ft wide. For an ADA route, confirm the 36 in clear-between-rails dimension on the 3 ft unit before relying on it; the 4 ft unit has margin over the requirement.
Sources
Every number in this guide comes from the 2010 ADA Standards for Accessible Design, 28 CFR Part 36 Appendix B and Appendix D, sections 403, 405, 505 and 1003.2.1. See ada.gov 2010 Standards, access-board.gov ADA Accessibility Standards, and the Access Board guide to Chapter 10, Boating Facilities.
Frequently asked questions
What is the maximum slope for an ADA ramp?
1:12, or 8.33%, under section 405.2. Every inch of rise needs a foot of horizontal run. Steeper slopes of 1:10 or 1:8 are allowed only in existing facilities with space limitations, and only for rises of 6 in and 3 in or less.
How much rise is allowed before a ramp needs a landing?
30 in per run (405.6). Each run needs a landing at top and bottom, at least 60 in long, and 60 in by 60 in where the ramp changes direction.
When does an ADA ramp need handrails?
When the rise exceeds 6 in (405.8). Handrails go on both sides, 34 in to 38 in high, extending 12 in past the top and bottom of the runs.
Why does low water matter for a gangway?
The floating dock drops with the water, so the gangway is steepest at low water. The low-water rise is the high-water rise plus the full water level change, and that condition decides whether the gangway is compliant.
Does a gangway have to be 1:12?
Not always. For gangways serving boat slips, 1003.2.1 EX 3 removes the 405.2 slope limit at 80 ft of gangway, and EX 4 does the same at 30 ft for facilities with fewer than 25 boat slips. Gangways on routes that do not serve boat slips must hold 1:12 at every water level.
Does a 3 ft wide gangway meet ADA width?
Only if it leaves 36 in clear between the handrails. There is no gangway exception to the 36 in clear width, so the clear dimension, not the nominal frame width, has to be confirmed.
Talk to Alummikon: 207-600-2705 or alummikon.com/contact-us
