Handrail Height and Grip

Rail height on the pitch line, the 12 in extensions, the graspable profile check, guard height, post spacing, and the load the rail has to carry.

A 7.75 in riser at a 10 in run gives a 37.7 degree slope, and a 36 in rail measured vertically above the nosing lands inside 34 to 38 in. The 12 in extensions at top and bottom are what make the rail continuous in the direction of travel.

—Rail height range on the pitch line
—Rail length with extensions
—Graspable profile check
—Guard height at the open side
—Post spacing and the load the rail carries
—Rail, brackets, and posts
How the math works
  • Height (IRC R311.7.8.4, IBC 1014.2): 34 to 38 in measured vertically from a line drawn through the nose of the treads (the pitch line). A stair with no risers measures from the walking surface, and a flight of a single riser needs no rail.
  • Extensions (R311.7.8.4, IBC 1014.2.1): the rail extends 12 in horizontally past the top riser and 12 in above the face of the bottom riser, and the extension runs in a plane parallel to the sloped top line of the rail. A rail that ends at a newel post at the top satisfies the top extension.
  • Graspable (IBC 1014.2 / IRC R311.7.8.5): the grip section is a max 2 in wide for a non-round profile, 6.25 in max perimeter, with finger clearance of 3/4 in at the back and a 3 in min corner radius, and a 1.5 in round rail is graspable by right. A 2x4 laid flat is a guard, not a grip, until you add a rail cap.
  • Continuity (R311.7.8.1): the rail is continuous along the sloped section, both sides of a stair 44 in wide or less, and the IBC requires the rail on both sides of a stair with the intermediate rail at 6 in max spacing on a 4 in sphere (the intermediate rail at 26 in max on a commercial guard, and 4 in sphere on any pattern).
  • Loads (IBC 1013.2 / 1607.8.3, IRC R301.1): a handrail carries 200 plf in any direction at the top, a guard carries 50 plf (residential, IRC R308) or 200 plf (commercial), and posts are the structural members: the 4x4 newel at a 4 ft spacing on a bracket is the usual residential answer, with a ledger rail and a post at each end.
Code-compliance check for planning, not an inspection. The IBC rail and guard provisions by occupancy, the residential 34 to 38 in measurement with no extensions on a stair with a single riser, the 44 in two-sided rule, the 4 in sphere at an intermediate rail, the 200 plf rail and 50 plf guard loads, and the newel-post footing at a deck are all code-edition and local items, and a rail on a deck guard is a structural connection to the house.

Is a stair handrail 34 or 38 inches?

Between 34 and 38 in measured vertically from the pitch line through the nose of the treads, and it is one number for the whole flight: 34 in at the bottom is 34 in at the top. The measurement is vertical, not square to the rail, so the bracket line sits at 41 to 46 in on a 37.7 degree stair. Commercial rails are the same 34 to 38 in band, and the rail must be continuous with the 12 in extensions on both sides of a stair in the IBC.

Can I use a 2x4 as a handrail?

A 2x4 laid flat has a 13 in perimeter, which fails the 6.25 in graspable perimeter, so it is legal as a guard member and not as a grip. Add a rail cap that is under 2 in wide with finger clearance and radiused corners, or use a 1.5 in pipe rail, which is graspable by dimension.

How far apart do handrail brackets go?

4 ft on center is the common bracket spacing for a 1.5 in pipe rail on a residential stair, with a post at each end, and a rail on a 36 in stair gets a center post at 44 in. Post spacing is a load path question: a rail carries 200 plf, and the posts carry it to the stringer, the floor, and the mudsill.

Related tools

Stair rise, run, headroomThe stair this rail sits on Deck board and framingGuards and rails on a deck Wall stud layout and platesWhere the newel posts land