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How Formwork Works

Balancing Quality, Cost and Safety

A common sentiment in the concrete industry is that formwork should balance quality, cost and safety. In terms of quality, forms should accurately create concrete structures to the architect-engineer's specifications, without causing bulges or other defects to the surface of the concrete. In terms of cost, we already mentioned that formwork comprises a good chunk of the project's concrete budget. Failure to finish formwork in a timely fashion can also delay the rest of the construction schedule and lead to additional labor expenses, giving concrete workers an incentive to work efficiently.

But safety trumps all. About 25 percent of all construction failures result from collapses and failure of concrete structures, and formwork failures account for more than half of the figure [source: Hanna]. In December 2011, a slab collapsed during the pouring of concrete during a casino construction project in Cincinnati, Ohio, resulting in several injuries to workers on the job site. The following month, another slab at different casino construction site collapsed during the concrete pour in Cleveland, Ohio [source: Feran].

Formwork has also caused hundreds of deaths on construction sites [source: Nemati]. In Bailey's Crossroads, Va., in 1972, workers removed the shores -- the supports that hold up horizontal slabs while the concrete sets -- from the 24th floor of an apartment building too early, triggering the collapse of the entire building, killing 14 workers and maiming many others [source: Hurd]. Forms can collapse from overloading with concrete, inadequate bracing, inadequate shoring, insufficient strength in the concrete before removal of the formwork, improper stripping and a host of other reasons.

Organizations like the Occupational Safety and Health Administration issue guidelines for designing and working with formwork. Having supervisors on site during the erection of the forms and the pouring of concrete can help minimize the hazards of using formwork. If the formwork design needs to be altered, contractors should consult the form designer ahead of time. Formwork might be a temporary structure, but its consequences to the structure and those who build it can be permanent.

For lots more information on the construction process, see the links on the next page.