A handrail is the part of a staircase that prevents falls, and building codes are strict about its height, grip and continuity. Before buying rail stock and brackets, you need its length along the slope, plus any extensions beyond the top and bottom steps.
The calculation
- Total rise = number of risers × riser height
- Total run = (number of risers − 1) × tread depth
- Sloped length = √(rise² + run²)
- Handrail length = sloped length + extensions
A straight stair has one fewer tread than risers, because the top riser leads onto the floor above.
Example
Fourteen risers of 7.5 in with 10 in treads give a total rise of 105 in and a run of 130 in. The sloped length is √(105² + 130²) ≈ 167 in, or 13.9 ft. Adding the ADA extensions of 12 in at the top and one tread depth at the bottom brings the rail to 15.8 ft, held by 5 brackets at 4 ft spacing.
Code requirements in the US
| Item | Typical rule |
|---|---|
| Height | 34 to 38 in above the tread nosings |
| When required | stairs with four or more risers (IRC) |
| Grip | round rail 1 1/4 to 2 in in diameter, or an equivalent graspable shape |
| Clearance from the wall | at least 1 1/2 in |
| Extensions | none for homes under the IRC; 12 in at the top and one tread at the bottom under the ADA |
Commercial and public buildings need handrails on both sides. Check your local code, which may amend these rules.
Brackets
Space wall brackets no more than about 4 ft apart, with one within a short distance of each end, and screw each one into a stud or blocking, not just into drywall. For heavy use, 3 ft spacing feels more solid.
Buying the stock
Handrail is sold in lengths of 8, 12 and 16 ft. One continuous piece looks better and is easier to grip; if you must join pieces, use a rail bolt and glue at a bracket. Add fittings such as returns to the wall at each end, which stop sleeves catching on an open end.
Limits
Winding or curved stairs and landings need fittings and a layout by eye. The angle check flags stairs steeper than about 42°, a sign that the riser height or tread depth may be outside code limits.