Scaffold stairway and stair tower

Stair flights with handrails built into their own tower in front of the scaffold, giving upright, hands-free access to every lift.

Also called: stair tower, stair unit, landing stair, aluminium stairway, scaffold stairs

Anyone who has to reach the fifth lift eight times a day with a bucket, toolbox or measuring kit soon learns to value a stair. The scaffold stairway replaces the ladder bay with proper treads and a handrail. You walk upright, your hand is free for the rail, and less practised people – site managers, surveyors, clients at handover – get up safely too.

It is the first choice on tall scaffolds or where several trades work at once, and usually stands as a separate stair tower in front of the scaffold; for access and industrial scaffolds there are also freestanding towers.

Components and variants

A stair tower is a basic scaffold – frames, or standards with ledgers – into which one flight is hung per lift.

• Landing stair: mostly aluminium, a flight with integrated landings at top and bottom. It hangs in a bay often 2.57 m long and climbs one lift of about 2 m.
• Stringers and treads: on modular systems separate stringers and treads are often combined, with the number of treads depending on length and height.
• Handrail: on the outside as a stair guard rail or double handrail, frequently with half couplers already fitted; an inner rail can be added.
• Same direction or switchback: either all flights run the same way and you walk a short distance along the scaffold at each lift, or they alternate and always arrive at the same point.

The tower is carried by normal frames or standards, or by dedicated stair uprights. The width of the stair bay depends on the system.

Building the tower

1. Fix the position, check the ground and set sole boards with base jacks.
2. Build the bottom level with deck transoms or base collars and level it.
3. Hang the first flight, add the next frames or standards and secure them against falling over.
4. Fit diagonals and rails and connect the stair guard rail.
5. Line the tower up with the scaffold and connect it at regular intervals, often every 4 m, with tube and couplers. Tie the scaffold at these points – even where it would otherwise need no tie.
6. Finish the top like the top lift of the scaffold, with full side protection and gap-free transitions.

Dismantling runs in reverse; the stair stays as long as anyone works above.

What to watch

• Ties: a stair tower has a large wind area and heavy traffic; missing connections are one of the commonest defects. Freestanding towers need ballast, guying or a structural calculation.
• Continuous handrail, including at the top exit, where a piece of rail is often missing.
• No storage on the stair: treads and landings are an escape route, not a shelf.
• Deformed stringers, cracked treads or loose hook-on claws mean rejection.
• Buying used: check hook claws, tread surfaces and welds, and make sure stair, rail and bay length suit the system you own.

Where there is no room for a tower, the ladder bay remains the alternative. Used stair units are listed under ladders and stairs.