What does OSHA do in construction?
The government agency responsible for regulating and legislating workplace safety is OSHA. Homeowners, contractors, or employees must understand the OSHA guideline to create a safe workplace. In 1970 the Occupational Safety and Health Act (OSHA) was created to ensure safe and healthful working conditions. OSHA's role of setting and enforcing standards is supplemented with training, outreach, education, and assistance to the workplace.
President Richard Nixon and United States Congress, with bipartisan support, created the national public health agency called OSHA with the fundamental proposition that no worker should choose between their lives and jobs. The creation of OSHA is considered a historical moment of cooperative national reform, making the right to a safe workplace a basic human right. Since the creation of workplace injuries, illnesses and fatalities have fallen dramatically.
OSHA is committed to protecting workers from safety hazards and toxic chemicals by ensuring at-risk workers have the information and education related to these hazards. OSHA provides employers with compliance assistance to promote best practices throughout the workplace.
The OSHA coverage includes most private sector employers, their workers, public sector employers, and workers in the 50 states, including most territories and jurisdictions under federal authority. Encouraging states and territories to develop an administrator OSHA approved their own safety and health programs OSHA will contribute up to fifty percent of the funding for the program.
OSHA's Construction standards protect workers from a wide range of serious hazards, including fall protection, cave-ins, confined spaces, exposure to harmful chemicals, machine guards, and respirators. OSHA has the availability to set and revised occupational safety and health standards at any time. The process involves many steps and opportunities for public engagement. When considering a new or revised standard, they often issue a Request for Information (RFI) or an Advance Notice of Proposed Rulemaking.
OSHA standards usually apply to areas not open to the public, and requirements are different from what you see in the residential and commercial building codes. Building a railing (guard rail) and Stair Railing standards defined by OSHA will not meet the IRC and IBC requirements.
Guardrail systems need to be smooth to protect employees from injuries and prevent catching or snagging of clothing. The top rails and midrails need to be at least 0.25-inches in diameter or thickness.
They are not to overhang the end posts except where it does not pose a hazard for employees. Post spacing needs to be 8-feet or less on center.
The guard railing must be 42 inches, +/- 3 inches, and may not exceed 45 inches above the walking-working surface on flat runs. This tolerance was established to meet the height requirement before and after a concrete pour on the walking surface. Midrails need to be at a height midway between the top edge of the guardrail system and the walking-working surface.
In some applications, a toe board is required to prevent objects, tools, and equipment from falling over the edge of a platform or roof. The toeboard must be 3.5 inches high with no gap greater than 1/4 inch between the toeboard and the walking-working surface. Often 2x4 lumber is used. A toeboard must be able to withstand a 50 lb force downward or outward.
A stair railing is required on stairs with four or more risers and needs to be 30 to 34 inches in height. Midrails need to be at a height midway between the top edge of the guardrail system and the stair tread. 
Besides Midrails, OSHA-compliant guard rails can also have infills of screens, mesh, intermediate vertical members, or solid panels. A midrail or infill is required with the gap between the top rail and the walking-working surface or pony wall exceeds 21 inches. Screens and mesh must extend from the walking-working surface to the top rail and across the entire opening between the top rail supports. Intermediate vertical members are no more than 19 inches apart. Architectural panels, screens, and mesh can not have spaces greater than 19 inches.
The load requirements for guardrails must be able to withstand a force of 200 pounds in both a downward or outward direction at any point along the top rail with a deflection of less than 2 inches. If a load of 200 pounds is applied downward on the top rail, the height can not deflect less than 39 inches above the walking surface. The infill must withstand a force of at least 150 pounds in any downward or outward direction across the panel. This load requirement limits the span between posts, wood guard rails will not meet a 6-foot span, and tube and pipe railings will not meet an 8-foot span.
