Handrails on Both Sides of the Stair

Why this matters

The residential code asks for one handrail. A person with one strong arm can use one handrail in one direction only. Going up, the rail on the left serves a strong left hand; coming down, that same rail is on her right, under the hand that does not grip. So she comes down sideways, or backward, or with her weak hand sliding along the rail, and the fall that ends her independence happens on the way down, which is where most stair falls happen. A second rail is a few hours of work. It is the change most often missing from a house that already "has a handrail."

What the code requires, and why it is a minimum

The International Residential Code (R311.7.8 in the 2021 edition, as adopted by your jurisdiction) requires a handrail on at least one side of each flight of stairs with four or more risers, at a height of 34 in to 38 in measured vertically from the sloped plane along the tread nosings. The same section requires the rail to be continuous for the full length of the flight, from directly above the top riser to directly above the lowest, with ends returned or terminating in newel posts or safety terminals, and with at least 1 1/2 in of space between the rail and an adjacent wall. It allows the rail to be interrupted by a newel post at a turn, and a volute or turnout over the lowest tread.

That is a minimum written for the general population. The 2010 ADA Standards, which do not govern a private home but are the best dimensional reference available, use handrails on both sides of a stair (504.6) at the same 34 in to 38 in (505.4). For many older and disabled users, both sides is the working requirement, whatever the code calls for. See related: What the ADA Does and Does Not Cover in a Private Home.

Why one rail is not enough for many people

• One-sided weakness. After a stroke, or with arthritis or an injury on one side, a person grips well with one hand only. A single rail serves that hand in one direction of travel and the weak hand in the other.
• Two-handed support. A person with weak legs often climbs by pulling with both arms, one on each rail, and descends the same way. On a stair about 36 in wide, rails on both walls sit about shoulder width apart, and a person can hold both at once.
• Carrying something. Laundry, a cane in the free hand, a hand on a child. With rails both sides, whichever hand is free has a rail.
• Fatigue. At the end of the day, or on the way down to a basement after a long one, the strong side tires. A second rail lets a person switch.

What makes a rail graspable

A handrail works when the hand can close around it in a power grip, fingers wrapping under and meeting the thumb, so a slip can be stopped by clenching. A wide flat board, a decorative rail molding, or the top cap of a guard is something to rest a palm on, not something to stop a fall with.

The IRC defines two graspable shapes (R311.7.8, 2021 edition):

• Type I: a circular cross section between 1 1/4 in and 2 in outside diameter, or a non-circular one with a perimeter between 4 in and 6 1/4 in and no cross-section dimension over 2 1/4 in.
• Type II: a larger profile, over 6 1/4 in of perimeter, permitted only with a finger recess on both sides that the fingers can curl into.

For an older user, and especially one with arthritis, the smaller end of Type I is the better choice: a round rail about 1 1/4 in to 1 1/2 in across lets a smaller or stiffer hand close fully. The rail has to be continuous along the gripping surface too: brackets mounted underneath, so the hand slides the full length without having to let go at each one.

Continuous runs, returns and extensions

Continuity. A rail that stops at a landing or a newel and restarts a few inches away makes the person let go, at exactly the point where they are changing direction. Where the stair has a landing, run the rail around it continuously if the geometry allows.

Returns. The end of a rail should turn back into the wall or down into a post. An open rail end catches a sleeve, a purse strap or a bathrobe belt and can pull a person off balance; a return removes the hook.

Extensions. The ADA reference carries the rail 12 in horizontally beyond the top riser (505.10.2) and, at the bottom, one tread depth beyond the last riser at the slope of the stair (505.10.3). The top extension matters most: it gives a person something to hold while they stand at the top, steady themselves and take the first step down, which is the most dangerous step on the stair. The IRC does not require the extension, so check that a top extension does not project into a door swing or a hallway path where it becomes something to walk into.

The load the rail has to carry

The IRC (Table R301.5, as adopted) sets a 200 lb concentrated load at any point along the top, in any direction, for handrails and guards. A rail on drywall anchors meets nothing. The structural rule and how to back a rail belong to See related: Grab Bar Backing and Load: The Structural Rule, and the method to See related: How to Add a Handrail That Actually Holds.

A worked example: the decorative rail on the wrong side

A 79-year-old woman has right-side weakness after a stroke; her left hand is strong. Her basement stair is a straight flight of 13 risers, enclosed by walls on both sides, 36 in between finished wall surfaces, with 10 in treads. It has one rail, on the left going up: a decorative profile 2 5/8 in wide at the top. She climbs well with her left hand on it. Coming down, she turns sideways and grips that same rail with her left hand, crossing her body, one step at a time.

What the code says of the existing stair: one rail on a 13-riser flight meets the one-side minimum. The rail profile does not: at 2 5/8 in across it exceeds the 2 1/4 in maximum cross-section dimension for a non-circular Type I rail, and it has no finger recess for Type II. It is a code-compliant number of rails with a non-compliant rail.

The work:

• Replace the left rail with a 1 1/2 in round rail on under-mounted brackets, continuous from directly above the top riser to directly above the bottom riser, returned to the wall at both ends.
• Add a matching rail on the right wall, same height, same profile. Coming down, that wall is on her left, under her strong hand, so she can face forward.
• Set both rails at 36 in above the nosing line, in the middle of the 34 in to 38 in range, so her hands sit level when she holds both.
• At the top, the hall continues straight past the stair, with no door swing, so both rails extend 12 in horizontally past the top riser before returning. At the bottom, a basement doorway sits close to the last tread on the right, so the right rail returns at the bottom riser without the one-tread extension, and the left rail extends 10 in at the slope.

Width check. The IRC (R311.7.1, as adopted) requires a stairway at least 36 in wide above the handrails, limits each rail to projecting no more than 4 1/2 in, and requires a clear width at and below the rail of at least 31 1/2 in with a rail on one side, or 27 in with rails on both. Each new rail, with its 1 1/2 in wall clearance and 1 1/2 in diameter, projects about 3 1/2 in once the bracket is counted. 36 minus 3 1/2 minus 3 1/2 leaves 29 in clear, which clears the 27 in both-sides minimum by 2 in. With one rail it would have left 32 1/2 in against 31 1/2 in.

The hazards in this job. Before drilling, scan both walls for studs, wiring and pipes, and keep drill holes out of the space directly above and below the light switch at the top of the stair, where cable usually runs. The house is from the 1950s, so the plaster may carry lead paint: mist before drilling, catch the dust on plastic, and clean with a HEPA vacuum rather than sweeping. Nobody uses the stair while the old rail is down and the new one is not yet fastened; she uses the other stair or waits upstairs. Work from the treads, not from a stepladder set on them, and keep the drill's cord off the steps.

Return to use. Before she touches it, the tech leans full body weight on each rail at every bracket, pulling out, pushing down and pushing sideways, and watches for any movement at the brackets or cracking in the plaster. Then she walks it, up and down, with the tech one step below her on the way down. She comes down facing forward, left hand on the right-wall rail.

What changes the answer

An open side with balusters. The guard's top cap is usually too wide to grip, so mount a graspable rail on the stair side of the guard posts, at 34 in to 38 in, rather than counting the cap as a rail. The guard's own height and load are separate requirements.

A stairlift. A stairlift's track runs along one side of the stair and takes some of the width; plan the rails and the track together, because the width check above changes and the rail on the track side may need a different bracket. See related: Stairlifts, Platform Lifts and Who May Install Them.

Winders. On a stair that turns with tapered treads, the safer walking line is usually on the wide side, so the rail on that side carries most of the load, and continuity around the turn matters more than on a straight flight.

A renter. Adding a rail is a modification the landlord may have to permit. See related: Reasonable Modifications for Tenants.

How to verify

Measure each rail's height from the nosing line at the top, middle and bottom of the flight, and record all three; a rail that is 36 in at the top and 33 in at the bottom fails the bottom of the range. Measure the wall clearance at several brackets. Have the person close their hand around the rail; if their fingers cannot meet their thumb, the profile is too big for them. Then watch them use both directions, at their usual time of day, and watch the first step down from the top in particular.

References

• International Residential Code, 2021 edition, R311.7.1, R311.7.8 and Table R301.5, as adopted by your jurisdiction
• U.S. Department of Justice, 2010 ADA Standards for Accessible Design, sections 504.6 and 505 (dimensional reference, not a requirement in a private home)
• See related: How to Add a Handrail That Actually Holds
• See related: Grab Bar Backing and Load: The Structural Rule; Contrast and Cues for Low Vision