Ramp Slope, Rise and Landings

Why this matters

A ramp that is too steep is worse than no ramp for some users, because it invites them onto a slope they cannot climb or cannot stop on. The usual failure is not ignorance of 1:12. It is measuring the rise at the door, building to that number, and finding the ground fell away under the run, so the finished ramp is steeper than drawn. The other failure is the ramp that meets every dimension and still cannot be used, because the landing at the top has a door swinging over it. Both are decided before the first post goes in.

The numbers the 2010 ADA Standards use

The 2010 ADA Standards do not govern a private home; they are the best dimensional reference available and the one an occupational therapist will expect to see. Treat these as a reference, not a requirement. See related: What the ADA Does and Does Not Cover in a Private Home.

For existing sites where space genuinely does not allow 1:12, Table 405.2 permits 1:10 for a total rise of 6 in or less and 1:8 for 3 in or less. Those are short-rise allowances, not a general relaxation.

Why steeper is dangerous, in numbers

On a slope, the force needed to push a chair uphill is close to the total weight of chair and rider multiplied by the slope ratio, for the shallow angles ramps use. That makes the comparison easy:

• At 1:12, the push is about one twelfth of the combined weight.
• At 1:8, it is one eighth. Divide one by the other and 1:8 takes 1.5 times the push of 1:12.
• At 1:6, it is twice the push of 1:12.

A self-propelled user does that work in strokes, and between strokes the chair wants to roll back. On a steep ramp the rider leans forward to keep the front casters down and the chair from tipping backward, which an older user with weak trunk muscles may not be able to do. Going down is the other half: the user controls speed by gripping the push rims, and on a steep ramp that means friction heat in the palms and a chair that can outrun them at the bottom. That is why the bottom landing matters as much as the top.

Cross slope gets less attention and causes more fatigue. A chair on a side slope steers toward the low edge, and the user corrects by pushing harder on one side for the whole length. A one-armed pusher, or someone after a stroke, may not be able to correct at all.

What the residential code says, and why you often need a permit

The International Residential Code has its own ramp section (R311.8 in the 2021 edition, as adopted by your jurisdiction). It is lighter than the ADA reference: a 1:12 maximum with a steeper allowance where 1:12 is technically infeasible, smaller minimum landings (3 ft by 3 ft), and handrail requirements tied to slope. Where the residential code is the law in your jurisdiction and the ADA reference is the better design, build to the reference and confirm with the inspector that it meets the code.

Separately, guards (the barrier that keeps someone from falling off an edge) are required on walking surfaces more than 30 in above the floor or grade below within 36 in horizontally, under IRC R312.1 as adopted. A tall entry ramp can cross that line partway along its length.

Whether a residential ramp needs a permit varies, and a shop should assume it might until the building department says otherwise. The reasons it often does:

• It is a structure attached to the house, with footings, and many jurisdictions treat it like a deck.
• It may sit in a setback. A front-yard ramp can run into zoning limits on how close a structure may sit to the lot line, and some jurisdictions have an administrative accessibility exception for exactly this.
• It is part of the egress path. A ramp from a required exit door changes how that door's landing is evaluated.
• An HOA or historic district may have its own approval, separate from the building permit.

Some jurisdictions exempt modular aluminum ramps or short ramps; others do not. Call before you quote, and put the answer in the job record.

A worked layout: the rise that was not what it looked like

The customer is a man who uses a manual chair he propels himself; his wife sometimes pushes on longer trips. The front door sits above a small porch. The tech measures from the top of the door threshold landing to the walk, and gets 24 in.

At 1:12, 24 in of rise needs 24 x 12 = 288 in of run, which is 24 ft. Under 30 in, so one run. Plus a 60 in landing at the top and 60 in at the bottom.

Then the tech runs a string line out 24 ft from the porch edge, levels it, and measures down to grade at the far end. The yard falls 2 in over that distance. The rise the ramp actually climbs is the porch landing to grade at the ramp's foot, so it is 24 + 2 = 26 in, not 24.

RAMP LAYOUT CARD - front entry
Rise at door (landing to walk)          24 in
Grade fall at ramp foot (string line)    2 in
Design rise, option A straight run      26 in
  run = 26 x 12                        312 in = 26 ft
  check: 26 in under 30 in max rise    one run
  re-check: string out to 26 ft, fall still 2 in
Landings: top 60 in, bottom 60 in
Footprint A: 26 + 5 + 5 ft             36 ft
Option B switchback, foot near house
  grade fall at foot                     1 in
  design rise                           25 in
  two runs of 12.5 in rise each
  each run = 12.5 x 12                 150 in = 12.5 ft
  turn landing                     60 x 60 in min
Handrails both sides (rise over 6 in)   yes
Guard check (over 30 in above grade)  no, max 25-26

Notice the re-check line. Lengthening the run moves the foot further out, where grade may fall further, so the string goes out to the new length before the number is trusted. Here the fall held at 2 in.

Option A needs 36 ft of straight run from the porch, which the front walk does not have before it meets the driveway. Option B folds the ramp back on itself. Its foot lands near the house where the yard has fallen only 1 in, so the rise is 25 in, split into two runs of 12.5 in, each 150 in long, joined by a turning landing. The turning landing has to hold both runs side by side plus rails, so it ends up wider than 60 in in practice; 60 by 60 is the minimum clear turning space, not the size of the platform.

The top landing gets one more check: the storm door swings out over it. A door sweeping 32 in of a 60 in landing leaves the chair user nowhere to sit while opening it. The tech either re-hangs the storm door to swing the other way, removes it, or makes the top landing deeper. That is the most common way a ramp passes every number and fails the person.

What changes the answer

The person may be better served by steps. A ramp is long, and for someone who walks with a cane and has poor endurance, 26 ft of incline can be harder than three steps with good rails on both sides. Ask what they do today, and watch them do it. See related: The Accessibility Walkthrough With the Person Who Lives There.

A power chair changes the push problem, not the descent problem. A power chair climbs 1:12 easily; what matters is control coming down and the stopping room at the bottom. Do not let "it's a power chair" talk the slope steeper, because the next chair may be manual, and a caregiver may be pushing.

Above about 30 in of rise, look at a lift. Two switchbacks and three landings can make a ramp bigger than the house front. A vertical platform lift takes a fraction of the footprint, and its installation is a licensed trade in many states. See related: Stairlifts, Platform Lifts and Who May Install Them.

Climate sets the surface. Where ice is a winter fact, an uncovered ramp is unusable for part of the year without a heated surface or a cover. A textured, drained surface is the minimum; standing water on a landing is ice by morning.

Mistakes that show up after the build

• The ramp foot ends on a sloped driveway or a lawn. The bottom landing has to be level and firm, and the path beyond it has to continue to somewhere a car can be met. A ramp onto grass is a ramp to nowhere in wet weather.
• Slope drifts along the run. Framing settles, posts heave, and a run built at 1:12 reads 1:11 at one section. A section steeper than the rest is where the push fails.
• Handrails stop at the end of the slope. The 12 in extension is what a person grips while their chair moves from slope to flat. Without it, the hand runs out of rail at the moment the chair changes angle.
• A threshold at the top. The ramp meets the landing perfectly and the door sill is a 1 in lip. See related: Thresholds and Changes in Level.

How to verify

Lay a 24 in digital level along the run at several points on each run, not just one, and record each reading. The 1:12 limit is about 4.8 degrees, so a reading over that at any point is a section to fix. Read cross slope the same way at the same points, against the 1:48 limit (about 1.2 degrees). Measure each landing clear of any door swing.

Then the user goes up and down under their own power, and again with whoever pushes them. Watch the top landing while they open the door, and the bottom landing while they stop.

References

• U.S. Department of Justice, 2010 ADA Standards for Accessible Design, sections 405 and 505 (dimensional reference, not a requirement in a private home)
• International Residential Code, 2021 edition, R311.8 (ramps) and R312.1 (guards), as adopted by your jurisdiction
• See related: How to Lay Out an Entry Ramp
• See related: The Ramp That Met Every Number and Still Did Not Work
• See related: Stairlifts, Platform Lifts and Who May Install Them