ADA Ramp Requirements
An ADA ramp may run no steeper than 1:12, which is one inch of rise for every twelve inches of run, or 8.33 percent. Each run may rise no more than 30 inches before a level landing, the clear width is 36 inches minimum, and handrails are required on both sides once the rise passes 6 inches. Steeper slopes of 1:10 and 1:8 exist in the standards, but only for alterations to existing buildings where space is limited, never for new construction.
The requirements, in one table
These are the figures from the 2010 ADA Standards for Accessible Design, with the section numbers so you can check any of them yourself. Everything below this table explains the ones that are commonly misapplied.
| Requirement | Value | Section |
|---|---|---|
| Change in level that needs a ramp | Greater than 1/2 inch | 303.4 |
| Slope at which a walking surface becomes a ramp | Steeper than 1:20 (5 percent) | 405.2 |
| Running slope, maximum | 1:12 (8.33 percent) | 405.2 |
| Cross slope, maximum | 1:48 (2.08 percent) | 405.3 |
| Clear width, minimum | 36 inches minimum; where handrails are provided, measured between their leading edges | 405.5 |
| Rise per run, maximum | 30 inches, with no limit on the number of runs | 405.6 |
| Landings | Level, at the top and bottom of every run | 405.7 |
| Landing clear length | 60 inches minimum | 405.7.3 |
| Landing clear width | At least as wide as the widest ramp run leading to it | 405.7.2 |
| Landing where a ramp changes direction | 60 inches wide by 60 inches long, clear | 405.7 |
| Handrails required when the rise exceeds | 6 inches, on both sides | 405.8 |
| Handrail height | 34 to 38 inches | 505 |
| Handrail extensions | 12 inches minimum, top and bottom of each run, with exceptions | 505.10 |
| Edge protection | Curbs, barriers or extended surfaces | 405.9 |
| Surface | Firm, stable and slip resistant | 302 |
| Curb ramps, selected figures only | Running slope 1:12 maximum, counter slope 1:20 maximum. Curb ramps are governed separately by 406, which also covers landings, flared sides, placement and transitions. This row is not a complete curb ramp checklist. | 406 |
When a slope legally becomes a ramp
This is the requirement that catches people, and it is not a matter of opinion. The US Access Board, the federal agency behind these standards, states it plainly in its own guide: portions of accessible routes with running slopes steeper than 5 percent must be treated as ramps.
That it is a mistake people actually make, rather than a technicality, is something the Justice Department recorded in a 1997 list of errors it was finding in new construction and alterations. That document has since been withdrawn as outdated, so it is no authority on what the rule is today, but it is a useful record of what went wrong on real sites. Its first ramp entry read:
Parts of an accessible route with slopes that exceed 1:20 lack required features including handrails and edge protection.
Read that carefully, because it is not describing a ramp that is too steep. The slope in that finding is legal. What is missing are the features that a slope of that steepness triggers.
Anything on an accessible route steeper than 1:20 is a ramp, whatever you call it and whatever it looks like. A gently sloping walk at 1:16 is not a walk with a bit of fall on it. It is a ramp, and it needs landings, edge protection, and handrails once its rise passes 6 inches.
The band that causes the trouble. At 1:20 or gentler, a sloping surface is a walking surface rather than a ramp, so the ramp requirements in 405 do not apply to it. It still has to meet the rules for walking surfaces, including the same 1:48 cross slope. Steeper than 1:12 and it is too steep to be a compliant ramp at all. Between those two, from just past 1:20 up to 1:12, it is a legal ramp that has to be built as one. That middle band is where a slope is gentle enough to look like a path and steep enough to be regulated as a ramp.
The second ramp entry on that same withdrawn list is worth knowing too: landings where ramps change direction, at switchbacks and 90 degree turns, being built too small. The figure is 60 inches by 60 inches clear, and a switchback that looks generous on a drawing can fall under it once handrails are added.
Rise, run, and why one long ramp is not allowed
At 1:12, every inch you need to climb costs a foot of ramp. That arithmetic is simple, and it is where a project usually discovers how much ground a ramp needs.
| Rise to climb | Run at 1:12 | Runs needed | Landings between runs |
|---|---|---|---|
| 6 inches | 6 feet | 1 | 0 |
| 12 inches | 12 feet | 1 | 0 |
| 24 inches | 24 feet | 1 | 0 |
| 30 inches | 30 feet | 1 | 0 |
| 36 inches | 36 feet | 2 | 1 |
| 60 inches | 60 feet | 2 | 1 |
The 30 inch limit in 405.6 is the part that surprises people. A single run may rise 30 inches and no more. There is no limit on how many runs a ramp has, so height is never the obstacle. Space is.
So a 36 inch rise cannot be one 36 foot run. It has to be at least two runs with a level landing between them, and that landing is not free: it takes 60 inches of its own, more if the ramp turns. A ramp climbing 36 inches in a straight line needs something like 41 feet of ground once the intermediate landing is counted, before the top and bottom landings are added.
This is why switchbacks exist, and why the 60 by 60 inch turning landing matters so much in practice. If you want to work the numbers for a specific rise, the wheelchair ramp slope calculator takes a rise and returns the run and the slope.
When a steeper ramp is permitted
The standards do contain slopes steeper than 1:12. They are narrow, and they are quoted out of context more often than any other figure on this page.
- 1:10 maximum, for a rise of no more than 6 inches.
- 1:8 maximum, for a rise of no more than 3 inches.
These are for alterations to existing buildings where space is limited. They are not available in new construction. The Department of Justice’s curb ramp guidance sets the same condition in plain words: the steeper slopes apply where “space limitations prohibit the use of a slope of 8.33 percent (1:12) or less”. If you are building something new, 1:12 is the limit, and running out of room is a design problem rather than a permitted exception.
Notice how small they are as well. A 1:8 slope is allowed to climb three inches, which is a run of two feet. These are provisions for meeting an existing threshold or a small step in a building that cannot be reconfigured. They are not a licence to build a shorter ramp because the compliant one will not fit.
Which version of the standards applies
There are two sets of ADA Standards in circulation, and a good deal of the guidance online still quotes the older one without saying so.
The 2010 Standards are the current ones. The Department of Justice states the changeover plainly: on or after March 15, 2012, all newly constructed or altered facilities must comply with all of the requirements in the 2010 Standards.
The difference is not academic. The 1991 Standards set the ramp cross slope at 1:50. The 2010 Standards set it at 1:48. Guidance quoting section 4.8 is using the 1991 numbering; the 2010 Standards number ramps at 405. If a page gives you a cross slope of 1:50, it is telling you what the rule used to be.
For an existing building, there is a provision people often reach for and often describe wrongly. The ADA National Network puts the distinction as sharply as it can be put:
The ADA does not have a provision to “grandfather” a facility but it does have a provision called “safe harbor.”
Safe harbor means that an element already complying with the 1991 Standards, and not being altered, does not have to be brought up to the 2010 Standards. It is element by element, not building by building. And it ends the moment you touch the element: alter something that met the 1991 Standards and the altered work has to meet the 2010 Standards.
The ADA is not your building code
The ADA is federal civil rights law. Your local building code is a separate obligation enforced by a different authority, and the two do not always print the same numbers.
Building code officials discuss this openly. On one code forum thread about a steep ramp at the entrance to a 1927 co-op, the replies turn on the New York City building code allowing a slope of 1 in 8 for pedestrian ramps that are not part of a means of egress, against the ADA’s 1 in 12. Both figures are real. They come from different documents with different scopes.
Meeting one does not discharge the other. A ramp can satisfy a local code and still leave the owner exposed under the ADA, and a plan reviewer’s approval is not a finding of ADA compliance. The project has to satisfy both. Where the same feature carries different minimums or maximums, the more restrictive value will normally control, but the two sets of requirements still have to be checked separately rather than assumed to line up.
Does any of this apply to a private house
Not directly. The ADA covers businesses that serve the public, which it calls public accommodations, along with commercial facilities such as offices, warehouses and factories. Restaurants, hotels, shops, private schools, doctors’ offices, day care centres and gyms are on that list. A home used only as a home is not.
So a ramp at your own front door is not an ADA matter, though your local building code may still have something to say about it, and a permit may still be required. Multi-family housing is a different question again and is dealt with by other legislation rather than by the ADA standards on this page.
The exception that catches people: running a business from home. If a place of public accommodation operates out of a residence, the business part is covered even though the home is not. The Justice Department’s regulation at 28 CFR 36.207 says the portion used exclusively as a residence is not covered, and that coverage extends to the elements used to enter the business, naming the homeowner’s front sidewalk, the door or entryway, and hallways, along with any areas customers or clients use, including restrooms. A therapist or accountant seeing clients at home is on the covered side of that line, and the ramp to the front door is part of what is covered.
Be careful with the home ramp advice you find. Steeper ratios such as 2:12 and 3:12 turn up as residential suggestions, including on pages that rank for this subject. Those are 16.7 percent and 25 percent, two and three times the ADA limit, and they are not ADA figures however they are presented. A steeper ramp is shorter and cheaper, and it is also harder to climb and faster to descend. If the person using it propels their own chair, the gentler slope is not a formality.
Plenty of people build to 1:12 at home for exactly that reason, without any obligation to. If you are weighing a ratio rather than checking a rule, the ramp slope calculator converts between a rise, a run, a percentage and an angle so you can see what a choice actually means underfoot.
Frequently asked questions
What is the maximum slope for an ADA ramp?
1:12, which is one inch of rise for every twelve inches of run, or 8.33 percent, or about 4.8 degrees. That is section 405.2 of the 2010 Standards.
The cross slope, measured across the width of the ramp rather than along it, is limited separately to 1:48.
How long does a ramp need to be?
At the maximum slope, one foot of ramp for every inch of rise. A 24 inch rise needs 24 feet of ramp.
Above a 30 inch rise you need more than one run, because 405.6 caps a single run at 30 inches of rise. Each additional run brings a level landing with it, so the total ground length grows faster than the slope arithmetic alone suggests.
Can I build a 1:8 ramp if 1:12 will not fit?
Only when you are altering an existing building and space limitations prevent a 1:12 slope, and only for a rise of 3 inches or less. The 1:10 allowance is the same idea with a 6 inch rise limit.
Neither is available in new construction. If a new ramp at 1:12 does not fit the site, that is a design constraint to solve, with switchbacks or a lift, rather than an exception you can claim.
When are handrails required on a ramp?
On both sides of any ramp run with a rise greater than 6 inches, under 405.8. They sit 34 to 38 inches above the ramp surface and extend at least 12 inches beyond the top and bottom of each run.
A rise of 6 inches or less does not require them, which is why short threshold ramps often have none. Edge protection is a separate requirement and is not satisfied by a handrail.
Is a gentle slope on a path a ramp?
If it is on an accessible route and steeper than 1:20, yes, and it has to be built as one with landings, edge protection and handrails where the rise calls for them.
The Access Board states the rule directly: a portion of an accessible route steeper than 5 percent is treated as a ramp. A withdrawn 1997 Justice Department list of construction errors recorded the same thing going wrong on real sites, routes over 1:20 built without handrails and edge protection. The slope itself is compliant. What is missing is everything that slope triggers.
Is my older building grandfathered in?
No. The ADA has no grandfather clause. What it has is safe harbor, which works element by element rather than building by building.
An element that already complied with the 1991 Standards and is not being altered may stay as it is. Alter it and the altered work has to meet the 2010 Standards, which have applied to all new construction and alterations since 15 March 2012.
Do ADA ramp rules apply to my house?
Generally no. The ADA covers businesses serving the public and commercial facilities, and a home used only as a home is not one of them.
The exception is running a business from the house. Under 28 CFR 36.207 the part used exclusively as a residence stays uncovered, but the business area is covered, and so are the elements used to get into it, which the regulation states includes the front sidewalk, the doorway and hallways. If clients come to your home office, the ramp to the door is in scope.
Your local building code may still apply and a permit may still be needed. Many people build to 1:12 at home anyway, because the reason for the number is that a steeper ramp is genuinely harder to use.
How wide does an ADA ramp have to be?
36 inches of clear width minimum, and where handrails are fitted that 36 inches is measured between them rather than to the outside of the structure.
It is a common way to end up narrow: the deck is built to 36 inches, the handrails are added inside that, and the clear width finishes under the minimum.