Guardrail systems are required to have a top edge height of 42 inches (1.1 m) plus or minus 3 inches (8 cm) above the walking/working level [1]. The height of the top edge may exceed 45 inches if the guardrail system meets all other criteria [1]. When employees are using stilts, the top edge height of the top rail should be increased by an amount equal to the height of the stilts [1]. Midrails, screens, mesh, intermediate vertical members, or equivalent intermediate structural members must be installed between the top edge of the guardrail system and the walking/working surface when there is no wall or parapet wall at least 21 inches (53 cm) high [1].

Additional guardrail requirements include:

• Midrails should be installed at a height midway between the top edge of the guardrail system and the platform surface [2].
• Screens and mesh should extend from the top edge of the guardrail system to the scaffold platform, along the entire opening between the supports [2].
• Intermediate members should not be more than 19 inches (48 cm) apart [2].
• Guardrail systems must be capable of withstanding a force of at least 200 pounds (890 N) applied within 2 inches (5.1 cm) of the top edge, in any outward or downward direction, at any point along the top edge [3].
• When the 200-pound test load is applied downward, the top edge of the guardrail should not deflect to a height less than 39 inches (1.0 m) above the walking/working level [3].
• Midrails, screens, mesh, intermediate vertical members, solid panels, and equivalent structural members must withstand a force of at least 150 pounds (666 N) applied in any downward or outward direction [3].
• Guardrail systems should be surfaced to prevent injury and snagging of clothing [3].
• The ends of top rails and midrails should not overhang terminal posts unless it doesn't create a projection hazard [3].
• Steel or plastic banding should not be used as top rails or midrails [3].
• Top rails and midrails should be at least one-quarter inch (0.6 cm) nominal diameter or thickness [3].
• If wire rope is used for top rails, it should be flagged at intervals of not more than 6 feet with high-visibility material [3].
• A chain, gate, or removable guardrail section should be placed across the access opening between guardrail sections when hoisting operations are not taking place in hoisting areas [3].
• Guardrail systems should be erected on all unprotected sides or edges of holes [3].
• When guardrail systems are used around holes for the passage of materials, the hole should have no more than two sides with removable guardrail sections. When the hole is not in use, it should be closed with a cover, or a guardrail system should be provided along all unprotected sides or edges [3].

For wood railings, wood components should be minimum 1500 lb-ft/in2 fiber (stress grade) construction grade lumber; the posts should be at least 2-inch by 4-inch (5 cm x 10 cm) lumber spaced not more than 8 feet (2.4 m) apart on centers; the top rail should be at least 2 inch by 4-inch (5 cm x 10 cm) lumber, the intermediate rail should be at least 1-inch by 6 inch (2.5 cm x 15 cm) lumber [4].

For pipe railings, posts, top rails, and intermediate railings should be at least one and one-half inches nominal diameter (schedule 40 pipe) with posts spaced not more than 8 feet (2.4 m) apart on centers [4].

For structural steel railings, posts, top rails, and intermediate rails should be at least 2 inch by 2-inch (5 cm x 10 cm) by 3/8-inch (1.1 cm) angles, with posts spaced not more than 8 feet (2.4 m) apart on centers [4].