Handrail Height, Grip, and Extensions (2010 ADA Standards 505)
34 to 38 in is the part everybody knows -- and it is a range, so a rail can be too HIGH.
Example
You enter
- Height to the top of the gripping surface (in) 36
- Clearance between the grip and the adjacent surface (in) 1.5
- Gripping surface circular
- Circular: outside diameter (in) 2.5
- Flight stair
- Tread depth, for the bottom extension at a stair (in) 11
- Top extension provided (in, horizontal) 12
- Bottom extension provided (in, horizontal) 12
You get
- Required top extension (in) 12
- Required bottom extension (in) 11
- Bottom vs flat (in) -1
- Clearance (1 1/2 in min) OK
Details, formula, and sources
Three others get missed. The clearance behind the grip is 1-1/2 in, which a wall bracket eats without anyone noticing. The grip is a WINDOW: a circular rail is 1-1/4 to 2 in, so a 2-1/2 in rail is too fat to grip and fails as surely as a thin one. And the extensions are ASYMMETRIC -- the top is a flat 12 in horizontal from the first riser nosing, but the bottom runs AT THE SLOPE for one TREAD DEPTH, so it is a function of the stair and on a 13 in tread the assumed 12 in is short.
height 34 in to 38 in to the top of the gripping surface, measured above walking surfaces, stair nosings, and ramp surfaces. Clearance behind the grip 1-1/2 in minimum. Circular grip 1-1/4 in to 2 in outside diameter; non-circular grip perimeter 4 in to 6-1/4 in AND cross-section dimension 2-1/4 in maximum. Extensions: 12 in horizontal at the top of a stair and at both ends of a ramp; at the bottom of a stair, one TREAD DEPTH of horizontal distance at the slope of the flight.
2010 ADA Standards for Accessible Design, 505.4, 505.5, 505.7.1, 505.7.2, 505.10.1, 505.10.2, and 505.10.3. A US federal standard in the public domain, quoted directly.
The 2010 ADA Standards are published in full at no cost at ada.gov and by the US Access Board.
Estimate. AHJ and licensed professional govern.
Field names used by the API: rail_height_in, clearance_in, grip_shape, diameter_in, flight_type, tread_depth_in, top_extension_in, bottom_extension_in, required_top_extension_in, required_bottom_extension_in, bottom_vs_flat_in, clearance_deficit_in
- Height 34 in minimum to 38 in maximum, to the top of the gripping surface above nosings2010 ADA Standards 505.4
- Clearance 1-1/2 in minimum between the gripping surface and adjacent surfaces2010 ADA Standards 505.5
- Circular grip 1-1/4 in minimum to 2 in maximum outside diameter2010 ADA Standards 505.7.1
- Non-circular grip perimeter 4 in to 6-1/4 in, and cross-section dimension 2-1/4 in maximum2010 ADA Standards 505.7.2
- Top extension at stairs 12 in horizontal beginning directly above the first riser nosing2010 ADA Standards 505.10.2
- Bottom extension at stairs one tread depth of horizontal distance, at the slope of the flight2010 ADA Standards 505.10.3
- Ramp extensions 12 in horizontal above the landing at both ends2010 ADA Standards 505.10.1