Concrete ADA Ramp Construction: Slope, Landings, and Handrails

A concrete ADA ramp meets federal requirements when its running slope stays at 1:12 or flatter, its clear width between handrails is at least 36 inches, and every 30 inches of vertical rise is broken by a level landing. Handrails on both sides are required whenever the rise exceeds six inches, edge protection keeps wheels and cane tips from slipping off, and the finished concrete surface has to stay slip-resistant in all weather. Everything else, from subgrade compaction to joint spacing, exists to keep those numbers true for the life of the slab.

Slope, Width, and Rise

The maximum running slope is 1:12: one inch of vertical rise for every twelve inches of horizontal run. Cross slope, measured across the ramp’s width, cannot exceed 1:48. Clear width between handrails must be at least 36 inches.¹

No single ramp run can rise more than 30 inches. After that, a level landing has to interrupt the slope before the next run begins.¹ There is no limit on how many runs a ramp can have. A doorway 30 inches off grade needs 30 feet of ramp at the steepest allowable slope. A 60-inch rise needs two 30-foot runs with a landing between them, and so on.

Work out the total run before you excavate. If the geometry doesn’t fit the site, the fix is switchbacks or a longer route, not a steeper pitch. Once concrete is poured at 1:10 because the space ran out, the only remedy is demolition.

Landings

Level landings are required at the top and bottom of every ramp and between every run. Landings cannot have a slope change greater than 1:48 in any direction and need to shed water. At the top and bottom, a landing must be at least 60 inches long in the direction of travel and at least as wide as the ramp.¹

Where a ramp changes direction at an intermediate landing, the landing has to give a full 60 inches by 60 inches of clear floor space. Handrails, posts, and edge protection cannot intrude on that square.¹ Switchback forms need to reflect that turning radius; a landing that looks square on paper often loses its clearance once the rails go in.

Handrails

Any ramp run rising more than six inches needs handrails on both sides. The top of the gripping surface sits between 34 and 38 inches above the ramp, measured vertically, at a consistent height along the entire run.²

Circular rails need an outside diameter between 1¼ and 2 inches. Non-circular rails need a perimeter between 4 and 6¼ inches, with no cross-section dimension larger than 2¼ inches. The gripping surface has to be continuous, with nothing blocking the top or sides. Obstructions along the bottom can cover no more than 20 percent of the length. Keep at least 1½ inches of clearance between the rail and any wall so a hand can slide without catching knuckles.²

At the top and bottom of each run, the handrail must extend horizontally at least 12 inches beyond where the slope begins or ends, then return to a wall, a guard, or the landing surface. Continuous rails at the inside turn of a switchback do not need extensions at the turn.²

Edge Protection

Edge protection keeps casters, cane tips, and crutch ends from sliding off the side of the ramp. Three approaches satisfy the requirement:¹

A curb at least 4 inches high.
A rail or barrier that will not pass a 4-inch diameter sphere.
The ramp and landing surfaces extended at least 12 inches beyond the inside face of the handrails.

For a concrete pour, the extended surface is usually the cleanest option. Making the slab wider than the handrail span adds material, but it removes the need for separate curb forms or mounted barriers, and it eliminates the drop-off entirely.

Slip-Resistant Surface

The ramp surface has to stay slip-resistant wet or dry. On concrete, that means a broom finish pulled perpendicular to the direction of travel while the slab is still workable. A steel-troweled or smooth finish will not pass inspection and turns dangerous under rain or ice. The broom grooves have to be cut at the right moment: too early and they close as the surface settles, too late and the bristles won’t bite deep enough to give traction.

When Detectable Warnings Apply

The raised truncated dome surfaces you see on curb ramps are required under the DOJ’s ADA Standards at transit facilities such as rail stations and bus stops. They are not required under DOJ’s standards at curb ramps for non-transit facilities like offices or retail stores, though many state and local codes require them anyway, and Federal Highway Administration projects require them regardless of facility type.¹ Check your local code before assuming they are optional. This does not apply to a typical building-entrance ramp; it’s a curb-ramp question.

Subgrade and Concrete Mix

A ramp that passes on the day of the pour can drift out of tolerance in a couple of winters if what’s under it isn’t right. Excavate to the full depth of the slab plus the aggregate base. Strip out organic material, roots, and topsoil, because anything that can decompose will leave voids. Compact the subgrade, then place a layer of compacted gravel or crushed stone, commonly four inches deep, for drainage and uniform bearing. Soft spots cause differential settlement, and once the slab tilts even slightly, the running or cross slope drifts out of range.

Specify concrete with a minimum 28-day compressive strength of 4,000 PSI to handle pedestrian and wheelchair loads through freeze-thaw cycles. Reinforce the slab at mid-depth with #4 rebar on a grid or heavy-gauge welded wire mesh. Four inches is the standard minimum thickness for pedestrian ramps; six inches is common where vehicles cross or heavy loads are expected.

Forming, Pouring, and Finishing

Wood or metal forms lock the slope in place. Stake and brace them against the lateral pressure of wet concrete. Before pouring, verify the slope with a digital level at several points along the run. Checking only the endpoints can hide a hump or dip in the middle that violates the continuous-slope requirement.

Place the concrete, screed it with a straightedge pulled in a sawing motion along the tops of the forms, then follow with a bull float or magnesium hand float to push aggregate down and close voids. Don’t over-work the surface. Pulling too much cream to the top weakens the wear layer that has to carry traffic for decades.

Once bleed water has evaporated and the surface has stiffened enough to hold texture, apply the broom finish across the direction of travel. This is one pass, at one window in the cure. Miss it and the slab either won’t take a groove or the grooves close before it sets.

Joints and Curing

Cut or tool control joints into the slab to steer shrinkage cracking to predictable lines. Space them at two to three times the slab thickness measured in feet, and never more than 15 feet apart on exterior flatwork. Joint depth should run about one-quarter of the slab thickness. Isolation joints separate the ramp from adjacent foundation walls, columns, or pavement so each element can move independently.

Cure the slab wet for at least seven days using damp burlap, plastic sheeting, or a spray-on curing compound. Rapid drying causes surface crazing and shrinkage cracks that undermine both durability and slip resistance. Pull forms only after the concrete can hold its own edges without chipping. Before opening the ramp for use, re-verify running slope, cross slope, and landing dimensions. Shrinkage and early settling can shift the numbers, and better to catch it before the first inspection than after.

Existing Sites Where 1:12 Isn’t Possible

New construction meets the full standard, period. Existing buildings are held to a different rule: barriers have to be removed where doing so is “readily achievable,” meaning without much difficulty or expense. When a ramp project counts as an alteration rather than simple barrier removal, the work has to comply with the full standards to the maximum extent feasible.³

Existing curb ramps have two narrow slope exceptions where space physically prevents 1:12:

Rise of 6 inches or less: slope may be as steep as 1:10.
Rise of 3 inches or less: slope may be as steep as 1:8.

These apply only where existing structural or site constraints make 1:12 impossible, not as a shortcut on new work.⁴ If full compliance is technically infeasible because it would require removing a load-bearing structural member or because dimensions are physically impossible on the site, the alteration still has to come as close to full compliance as conditions allow.

Tax Credits and Deductions

Two federal incentives can offset a real share of the cost. The Disabled Access Credit under IRC Section 44 is available to businesses that earned $1 million or less or had no more than 30 full-time employees in the prior year. It covers 50 percent of eligible access expenditures that exceed $250 but do not exceed $10,250 in a given year, for a maximum annual credit of $5,000. Qualifying businesses can claim it every year they spend on access.⁵

The Architectural Barrier Removal Deduction under IRC Section 190 lets any business, regardless of size, deduct up to $15,000 per year for costs of removing architectural and transportation barriers at existing facilities.⁶ A small business that qualifies for both can use them together: the Section 44 credit on the first $10,250 of expenses, then the Section 190 deduction on additional costs up to the $15,000 cap.

Keeping the Ramp Compliant Over Time

Compliance drifts. Ground settles, frost heaves, surfaces polish under traffic, and staff put planters and trash cans on landings that used to be clear. The U.S. Access Board has noted that building to a running slope of 7.5 percent instead of the maximum 8.33 percent, and a cross slope of 1.5 percent instead of the maximum 2.08 percent, creates a tolerance buffer that absorbs small movement without pushing the ramp out of compliance.¹ It costs almost nothing to specify at pour time and it’s far cheaper than grinding or overlaying a slab that has shifted half a percent.

Recheck slopes periodically. Watch for vertical discontinuities at joints and slab edges: changes in level greater than half an inch require a ramp of their own, and even smaller lips can catch casters. Seal control joints as part of routine maintenance to keep water out of the subgrade. When a section settles enough to alter the slope, remove and re-pour that section. Thin overlays rarely bond reliably to weathered concrete and tend to create their own trip hazards.

1
U.S. Access Board. Guide to the ADA Accessibility Standards – Chapter 4 Ramps and Curb Ramps
2
U.S. Access Board. Americans with Disabilities Act Chapter 5 General Site and Building Elements
3
ADA.gov. ADA Readily Achievable Barrier Removal Checklist for Existing Facilities
4
ADA.gov. Curb Ramps and Pedestrian Crossings Under Title II of the ADA
5
Office of the Law Revision Counsel. 26 USC 44 – Expenditures to Provide Access to Disabled Individuals
6
Office of the Law Revision Counsel. 26 USC 190 – Expenditures to Remove Architectural and Transportation Barriers