Suspended Scaffold Outrigger Counterweight

The physical weight looks absurd next to the platform. An outrigger reaching eighteen inches inboard and six feet outboard carries a four-to-one disadvantage before any factor of safety, so a fifteen hundred pound suspended load needs six thousand pounds just to balance -- and a four-to-one factor against overturning puts the requirement into the tens of thousands per outrigger. Shortening the outboard reach or lengthening the inboard arm are the only two levers, and the inboard arm needed for a target counterweight is reported here because that is the one a crew can usually move. THE LOAD TO USE IS THE PLATFORM'S RATED LOAD, not what happens to be on it. The scaffold is designed to carry that load and the counterweight has to hold it down whether or not today's crew intends to use it -- a counterweight sized for two workers is inadequate the day someone stages material, and nobody re-runs the arithmetic before doing that. TWO REQUIREMENTS SIT ALONGSIDE THE WEIGHT AND ARE NOT SUBSTITUTES FOR IT. Counterweights must be non-flowable and secured to the outrigger: sand bags, water containers, masonry units, and loose material are prohibited because they leak, are removed, or get borrowed for other work, and a counterweight that walks away is the classic failure on this equipment. And a TIEBACK to independent structural anchorage is required in addition to the counterweight, so that the outrigger cannot slide or rotate even if the counterweight is disturbed. The anchorage that tieback goes to has its own requirement and is not a parapet clamp on a cornice. A static moment balance on one outrigger. It does not design the outrigger, the beam, its bearing on the roof, or the roof's ability to take the concentrated loads at both ends -- a counterweight of this size sitting on a roof is itself a structural question. It does not address the tieback capacity or its anchorage, the suspension ropes, the hoists, the secondary lines, or the personal fall arrest that is required independently of everything here. It does not cover parapet clamps, roof cars, or transportable outrigger systems, each of which has its own criteria. Suspended scaffolds kill people. OSHA 29 CFR 1926 Subpart L, the manufacturer's instructions, and the qualified person who designs the rigging govern.

rated load x outboard arm = counterweight x inboard arm, so the required counterweight = rated load x (outboard / inboard) x the factor of safety; the achieved factor is the resisting moment over the overturning moment.

The outrigger moment balance by name, with 4:1 against overturning the common requirement. The load used is the platform's RATED load, not its empty weight and not what happens to be on it. Counterweights must be non-flowable and secured to the outrigger, and a TIEBACK to independent structural anchorage is required IN ADDITION and is not a substitute. OSHA 29 CFR 1926 Subpart L, the manufacturer's instructions, and the qualified person who designs the rigging govern.

One lever ratio and one multiplication; no manufacturer rigging table is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: rated_load_lb, outboard_arm_ft, inboard_arm_ft, factor_of_safety, counterweight_unit_lb, target_counterweight_lb, lever_ratio, overturning_moment_ft_lb, balance_counterweight_lb, required_counterweight_lb, counterweight_units, resisting_moment_ft_lb, achieved_fos, inboard_for_target_ft

• The RATED load, not today's load a counterweight sized for two workers fails the day someone stages materialthe manufacturer's instructions
• A static balance on one outrigger the roof's ability to take the concentrated loads is a separate questionthe qualified person who designs the rigging
• Tieback and anchorage not evaluated required in addition to the counterweight, and not a parapet clamp on a corniceOSHA 29 CFR 1926 Subpart L