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Engineering Controls Database

Construction Guardrails

In the construction industry, injuries and fatalities caused by falls-from-elevation are serious problems in United States workplaces.
In 2008, 975 workers were killed in construction, 336 (34%) involved falling. Of these 336 fatalities, 113 (34%) involved workers falling from a roof edge, through roof and floor openings, or through skylights.

Thousands of serious non-fatal injuries also result from fall-through events. Serious injuries are de?ned by the Bureau of Labor Statistics as those that cause a worker to miss at least one day away from work (DAFW) beyond the day the incident occurred. An analysis of the Survey of Occupational Injuries and Illnesses for the five-year period of 2003-2007 indicated that 4,870 serious injuries occurred when workers fell through roof holes, ?oor holes, and skylights. These falls resulted in an estimate of 89,315 total DAFW [Bobick et al. 2010].
Researchers at NIOSH’s Division of Safety Research developed a patented multifunctional guardrail system that can help protect construction workers from injuries and fatalities due to falls to lower levels. The initial design, developed for residential roofing applications, was based on the footprint of the commonly used roof bracket, 3 inches wide by 18 inches long, that uses three 16-penny (16d) nails to attach the bracket (photo 1) to a sheathed roof truss.
photo 1

photo 1

Photo 2 depicts the NIOSH-designed roof bracket-guardrail system. The roof bracket base is designed to be used on flat surfaces and can be adjusted to seven roof slopes [6/12, 8/12, 10/12, 12/12, 15/12, 18/12 and 24/12 - or 27°, 34°, 40°, 45°, 51°, 56° and 63° (A-frame)].
photo 2

photo 2

As the roof slope increases in steepness, the vertical tube that supports the top rail and midrail will lean backward from vertical; this may cause the height of the top rail to be less than the 39-inch minimum required by the Occupational Safety and Health Administration (OSHA) regulation 29 CFR 1926.502(b)(1). To ensure the height regulation is met, the NIOSH system has been designed so the fixtures that support the top rail and midrail can be adjusted. Fixtures are loosened with a handle at the back of the fixture that permits it to be slid up the vertical tube to the required OSHA height.

OSHA regulation 29 CR 1926.502(b)(3) requires that a guardrail structure be able to withstand a 200-lb force (such as a worker weighing 200 lbs or more falling into the guardrail). Lab testing has verified that hand tightening is sufficient to ensure that cross-members will not slip down the vertical tube when contacted with a 200-lb force, as specified by OSHA. In fact, the system has successfully supported an impact force of 435 lb (more than twice the OSHA requirement) from a test manikin that fell against the top rail without slippage or failure of any components [McKenzie et al. 2004; Bobick & McKenzie 2005].
Bobick TG, McKenzie EA Jr. [2005]. Using guardrail systems to prevent falls through roof and floor holes. Proceedings of the 2005 ASSE Professional Development Conference, New Orleans, LA, USA.

Bobick TG, McKenzie EA Jr., Kau TS [2010]. Evaluation of guardrail systems for preventing falls through roof and floor holes. J Saf Rsch 4:203-211.

Bobick TG, McKenzie EA Jr. [2011]. Construction guardrails: development of a multifunctional system. Prof Saf 56(1):48-54.

McKenzie EA Jr., Bobick TG, Cantis DM [2004]. Design of testing apparatus to evaluate the strength of guardrail systems. Proceedings of ASME International Mechanical Engineering Congress and Exposition, USA.