Accessible reach ranges, protrusions, and floor transitions

One-line orientation

Accessibility rules separately limit how high a person must reach, how far an object may project into a path, and how a floor level may change. Their numbers are easy to confuse.

Key points

Reach range (general): accessible controls, switches, and outlets must fall between 15 inches and 48 inches AFF — the zone a seated wheelchair user can reach without overexertion.
Side reach is NOT higher: the 2010 ADA Standards cap the unobstructed side reach at the same 48 inches (§308.3.1) — the 54-inch side-reach maximum comes from the superseded 1991 ADAAG. Reaching over an obstruction can lower the allowed height (48” over an obstruction up to 10” deep; 46” over one 10–24” deep).
Protrusion limit: objects may project no more than 4 inches into a circulation path. If the protrusion exceeds 4 inches, a barrier (railing, curb, low wall) or recessing is required to signal its presence.
Protrusion hazard zone: the dangerous band is 27 to 80 inches AFF. Below 27 inches a cane can detect the object; above 80 inches the object clears head height. Between those values the obstruction is invisible to cane users — the source of the rule.
Floor transitions — vertical: a change in floor level up to 1/4 inch may be vertical (no bevel needed).
Floor transitions — beveled: between 1/4 inch and 1/2 inch total height, a bevel at a maximum slope of 1:2 is required. A change exceeding 1/2 inch is no longer a transition — it becomes a ramp.

Confusions / comparison

Rule	Lower limit	Upper limit	Note
Reach range	15” AFF	48” AFF (forward and side)	Controls, outlets, thermostats
Protrusion hazard zone	27” AFF	80” AFF	Objects here must be ≤ 4” deep or mitigated
Floor transition — vertical	0	≤ 1/4”	No bevel required
Floor transition — beveled	> 1/4”	≤ 1/2”	Bevel ≤ 1:2 required
Transition too tall	> 1/2”	—	Must be treated as a ramp

Protrusion detail	Limit
Max depth into path	4 inches
Hazard zone (height)	27”–80” AFF
Mitigation if > 4”	Barrier, curb, recessing, or ground-level indicator

Exam pitfalls

The 27–80” protrusion zone is the trap, not the depth limit. Exam scenarios often ask which protrusion is hazardous. Something mounted at 12 inches AFF (below 27”) can be felt by a cane — it is not in the danger zone. Something at 48 inches sticking out more than 4 inches is hazardous.
54 inches is an outdated answer, not a side-reach bonus. Under the 2010 ADA Standards the unobstructed high reach is 48 inches for both forward and side approaches (§308). The 54-inch side reach was the 1991 ADAAG rule and survives only in narrow exceptions (e.g., fuel dispensers on existing curbs) — picking 54” is the classic outdated-standard trap.
The bevel rule and the threshold rule are the same number. Both cap at 1/2 inch total with a bevel above 1/4 inch. A door threshold and a floor transition follow identical logic — useful to remember as a single rule.
Reach range applies to all operable elements. Light switches, thermostats, intercoms, fire alarm pull stations, and electrical outlets all fall under the 15”–48” band. A pull station at 54 inches fails the 2010 Standards — it sits above the 48-inch maximum.

→ Accessible doors (this topic): the 1/4”/1/2” bevel threshold recurs at door thresholds · Accessible routes (this topic): the passageway width and cane-detection logic connect here · Accessible bathrooms (this topic): grab-bar and control heights fall within the reach range.

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One-line orientation

Key points

Confusions / comparison

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