Scaffold Dismantle Sequence Calculator

How to work it out

1. Count the lifts first: height ÷ lift height, rounded up. 20 m at 1.8 m lifts is 12 lifts — that is how many levels come down.
2. Decide the sections: adjacent sections must not differ by more than two lifts (3.6 m at 1.8 m lifts). Beyond that, extra ties must be added to that section, otherwise the two halves behave independently and the joint goes first.
3. Fix the order within each lift: boards off, then netting and toe boards, then transoms, then ledgers, then standards. Never pull a member out of the middle and never work at two levels at once.
4. Take the ties out lift by lift, with the frame. Never strip a whole floor or several floors of ties and come back for the scaffold later — that is the single most common cause of dismantling collapses.
5. When only about 6.5 m is left (roughly the fourth lift at 1.8 m lifts, 7.2 m elevation), install temporary raking props on the outside first, then remove the ties at that level. That stub has no frame above it and almost no ties left, which makes it the least stable it will ever be.
6. Lower components on a rope or in a chute — never throw them. Sort tubes, couplers and boards on the ground and count them the same day, so shortages are found while the crew is still on site.

Where it goes wrong

• Ties out before the frame — the most common and most lethal mistake. Ties are the only members transferring horizontal load into the structure; strip a whole floor and the frame becomes a free-standing set of tubes that self-weight, people and material will topple. Investigation reports into dismantling collapses cite exactly this as the direct cause.
• Working top and bottom at once — one dropped 6 m tube is a serious injury. The code prohibits it; the area below needs exclusion and a banksman.
• Sections more than two lifts apart with no extra ties — each section then stands on its own and the joint fails first. The code requires added ties beyond a two-lift step.
• Removing the ties at the bottom without props — the frame gets shorter and less restrained as you go down, so the last stub is the most dangerous part. Props go in at about 6.5 m, normally at 45 to 60 degrees to the ground.
• Stacking stripped tubes and couplers on the scaffold — the frame is already partly dismantled and weaker, and several tonnes of stock on it is load you added yourself. Components come down as they are stripped, not later.

On site

• Four things before anyone touches a coupler: check the coupler connections, ties and bracing against the design; revise the sequence in the method statement and get it approved; brief the crew; and clear debris from the scaffold and obstructions from the ground.
• A named person must direct the work. Where several people work at once, split the tasks, keep them in step and give each enough room — do not crowd one spot.
• Land-based tubular scaffolds 24 m and above are high-risk works, so the method statement needs the contractor's technical lead and the chief supervising engineer to sign; 50 m and above also needs an expert review panel. Get the paperwork and the briefing done before stripping starts — those two sheets are what separates compliance from liability.

Basis

• EN 12811-1:2003 (work scaffolds — assembly, use and dismantling)
• NASC TG20:21 (tie duty, alteration and dismantling sequence)
• BS 5975:2019 (temporary works coordination and supervision)
• OSHA 29 CFR 1926.451(c) (guys, ties and braces during erection and dismantling)