What is a switchback staircase?
It's the stair that turns back on itself at a mid-landing. The reason you see it everywhere in warehouses and stair towers isn't aesthetics — it's a floor-space answer to a building-code rule.
Short answer: a switchback staircase is two flights of stairs running in opposite directions, joined by an intermediate landing where the path reverses 180°. Also called a half-turn or U-shaped stair, it packs the same rise into roughly half the length of a straight run — the standard solution when a stair is tall and floor space is tight.
How it's built
You climb the first flight, reach a landing, turn 180°, and climb the second flight running back parallel to the first. The two flights sit side by side, so the overall plan is a compact rectangle instead of one long diagonal. Add more flights and landings and the same pattern stacks vertically through multiple storeys — that's a switchback stair tower.
Why it exists: the 16-riser rule
This is the part most people miss. The Ontario Building Code limits a single flight to a maximum of 16 risers — about 9 ft of rise — before an intermediate landing is required (OBC §3.4.6). Once a stair is tall enough to cross that threshold, a landing is mandatory regardless of layout. A switchback simply uses that required landing as the turning point, folding the stair back on itself instead of running it out in a straight line.
The landing has to be at least as deep as the stair is wide (OBC §3.4.6), and it resets the riser count so the next flight can run another full 16. Risers and treads must stay uniform across every flight — a change in dimension between flights is a fail at inspection.
When a switchback is the right call
- Tall rises in a tight footprint — mezzanine access, multi-storey egress, equipment mezzanines where a straight run would eat the floor.
- Egress stair towers — the half-turn geometry stacks cleanly through floors. See egress staircases.
- Where a landing is already required — if the rise forces a mid-landing anyway, turning the stair is usually the efficient use of it.
When it isn't
- Short rises under ~9 ft — a straight-run stair is simpler and cheaper when no landing is required.
- Long, low spaces — if floor length is plentiful and headroom isn't, a straight run can be the better fit.
- Pure equipment access with no occupant load — a ship's ladder may be permitted and far more compact.
Frequently asked
What is a switchback staircase?
Why use a switchback stair instead of a straight run?
What is the difference between a switchback and a dog-leg stair?
How big does the landing on a switchback stair need to be?
- Switchback stairs — fabrication & install
- OBC 2024 stair code guide — the full rule set
- Straight-run stairs — the simpler alternative
- Steel stairs pillar