Scaffolding » General Requirements for Scaffolds [29 CFR 1926.451]
Each scaffold and scaffold component must support without failure its own weight and at least 4 times the maximum intended load applied or transmitted to it. [29 CFR 1926.451(a)(1)] A qualified person must design the scaffolds, which are loaded in accordance with that design. [29 CFR 1926.451(a)(6)] Scaffolds and scaffold components must not be loaded in excess of their maximum intended loads or rated capacities, whichever is less. [29 CFR 1926.451(f)(1)] Load carrying timber members should be a minimum of 1,500 lb-f/in2 construction grade lumber. [29 CFR 1926 Subpart L Appendix A(1)(a)]
Scaffold Platform Construction
Each platform must be planked and decked as fully as possible with the space between the platform and uprights not more than 1 inch (2.5 cm) wide. The space must not exceed 9½ inches (24.1 cm) when side brackets or odd-shaped structures result in a wider opening between the platform and the uprights. [29 CFR 1926.451(b)(1)]
Scaffold planking must be able to support, without failure, its own weight and at least four times the intended load. [29 CFR 1926.451(a)(1)]
Solid sawn wood, fabricated planks, and fabricated platforms may be used as scaffold planks following the recommendations by the manufacturer or a lumber grading association or inspection agency. [29 CFR 1926 Subpart L Appendix A(1)(b) & (c)]
Tables showing maximum permissible spans, rated load capacity, and nominal thickness are in 29 CFR 1926 Subpart L Appendix A(1)(b) & (c) of the standard.
The platform must not deflect more than 1/60 of the span when loaded. [29 CFR 1926.451(f)(16)]
The standard prohibits work on platforms cluttered with debris. [29 CFR 1926.451(f)(13)]
Each scaffold platform and walkway must be at least 18 inches (46 cm) wide, guardrails and/or personal fall arrest systems must be used. [29 CFR 1926.451(b)(2)]
The standard requires employers to protect each employee on a scaffold more than 10 feet (3.1 m) above a lower level from falling to that lower level. [29 CFR 1926.451(g)(1)]
To ensure adequate protection, install guardrails along all open sides and ends before releasing the scaffold for use by employees, other than the erection and dismantling crews. [29 CFR 1926.451(g)(4)(i)]
Guardrails are not required, however:
- When the front end of all platforms are less than 14 inches (36 cm) from the face of the work. [29 CFR 1926.451(b)(3)]
- When outrigger scaffolds are 3 inches (8 cm) or less from the front edge. [29 CFR 1926.451(b)(3)(i)]
- When employees are plastering and lathing 18 inches (46 cm) or less from the front edge. [29 CFR 1926.451(b)(3)(ii)]
Steel or plastic banding must not be used as a toprail or a midrail. [29 CFR 1926.451(g)(4)(xiii)]
Criteria for Supported Scaffolds
Supported scaffolds are platforms supported by legs, outrigger beams, brackets, poles, frames, or similar rigid support. [29 CFR 1926.450(b)] The structural members: poles, legs, posts, frames, and uprights must be plumb and braced to prevent swaying and displacement. [29 CFR 1926.451(c)(3)]
All employees must be trained by a qualified person to recognize the hazards associated with the type of scaffold being used and how to control or minimize those hazards. The training must include fall hazards, falling object hazards, electrical hazards, proper use of the scaffold, and handling of materials. [29 CFR 1926.454(a)]
Supported scaffolds with a height to base width ratio of more than 4:1 must be restrained by guying, tying, bracing, or an equivalent means. [29 CFR 1926.451(c)(1)]
Either the manufacturers' recommendation or the following placements must be used for guys, ties, and braces:
- Install guys, ties, or braces at the closest horizontal member to the 4:1 height and repeat vertically with the top restraint no further than the 4:1 height from the top.
- Vertically - every 20 feet (6.1 m) or less for scaffolds less than 3 feet (0.91 m) wide; every 26 feet (7.9 m) or less for scaffolds more than 3 feet (0.91 m) wide.
- Horizontally - at each end; at intervals not to exceed 30 feet (9.1 m) from one end. [29 CFR 1926.451(c)(1)]
Supported scaffolds' poles, legs, posts, frames, and uprights must bear on base plates and mud sills, or other adequate firm foundation. [29 CFR 1926.451(c)(2)(i) and 29 CFR 1926.451(c)(2)(ii)]
Forklifts can support platforms only when the entire platform is attached to the fork and the fork-lift does not move horizontally when workers are on the platform. [29 CFR 1926.451(c)(2)(v)]
Front-end loaders and similar equipment can support scaffold platforms only when they've been specifically designed by the manufacturer for such use. [29 CFR 1926.451(c)(2)(iv)]
Also see, OSHA Standards Interpretation and Compliance Letter: 09/30/1999 - Forklifts in construction: Elevating personnel and operator training.
What materials can be used to increase the working level height of employees on supported scaffolds?
Stilts may be used on a large area scaffold. When a guardrail system is used, the guardrail height must be increased in height equal to the height of the stilts. The manufacturer must approve any alterations to the stilts. [29 CFR 1926.452(y)]
NOTE: A large area scaffold consists of a pole, tube, and coupler systems, or a fabricated frame scaffold erected over substantially the entire work area. [29 CFR 1926.450(b)]
Criteria for Suspended Scaffolds
A suspension scaffold contains one or more platforms suspended by ropes or other non-rigid means from an overhead structure, 29 CFR 1926.450(b), such as the following scaffolds: single-point, multi-point, multi-level, two-point, adjustable, boatswain's chair, catenary, chimney hoist, continuous run, elevator false car, go-devils, interior hung, masons', and stone setters'.
Some of the requirements for all types of suspension scaffolds include:
- Employers must ensure that all employees are trained to recognize the hazards associated with the type of scaffold being used. [29 CFR 1926.454(a)]
- All support devices must rest on surfaces capable of supporting at least four times the load imposed on them by the scaffold when operating at the rated load of the hoist, or at least one-and-a-half times the load imposed on them by the scaffold at the stall capacity of the hoist, whichever is greater. [29 CFR 1926.451(d)(1)]
- A competent person must evaluate all direct connections prior to use to confirm that the supporting surfaces are able to support the imposed load. [29 CFR 1926.451(d)(3)(i)]
- All suspension scaffolds must be tied or otherwise secured to prevent them from swaying, as determined by a competent person. [29 CFR 1926.451(d)(18)]
- Guardrails, a personal fall-arrest system, or both must protect each employee more than 10 feet (3.1 m) above a lower level from falling. [29 CFR 1926.451(g)]
- A competent person must inspect ropes for defects prior to each workshift and after every occurrence that could affect a rope's integrity. [29 CFR 1926.451(d)(10)]
- When scaffold platforms are more than 24 inches (61 cm) above or below a point of access, ladders, ramps, walkways, or similar surfaces must be used. [29 CFR 1926.451(e)(1)]
- When using direct access, the surface must not be more than 24 inches (61 cm) above or 14 inches (36 cm) horizontally from the surface. [29 CFR 1926.451(e)(8)]
- When lanyards are connected to horizontal lifelines or structural members on single-point or two-point adjustable scaffolds, the scaffold must have additional independent support lines equal in number and strength to the suspension lines and have automatic locking devices. [29 CFR 1926.451(g)(3)(iii)]
- Emergency escape and rescue devices must not be used as working platforms, unless designed to function as suspension scaffolds and emergency systems. [29 CFR 1926.451(d)(19)]
Counterweights used to balance adjustable suspension scaffolds must be able to resist at least four times the tipping moment imposed by the scaffold operating at either the rated load of the hoist, or one-and-a-half (minimum) times the tipping moment imposed by the scaffold operating at the stall load of the hoist, whichever is greater. [29 CFR 1926.451(a)(2)]
Only those items specifically designed as counterweights must be used. [29 CFR 1926.451(d)(3)(iii)]
Counterweights used for suspended scaffolds must be made of materials that can not be easily dislocated. Flowable material, such as sand or water, cannot be used. [29 CFR 1926.451(d)(3)(ii)]
Counterweights must be secured by mechanical means to the outrigger beams. [29 CFR 1926.451(d)(3)(iv)]
Vertical lifelines must not be fastened to counterweights. [29 CFR 1926.451(g)(3)(i)]
No. Such materials cannot be used as counterweights. [29 CFR 1926.451(d)(3)(ii) and 29 CFR 1926.451(d)(3)(iii)]
Outrigger beams (thrustouts) are the structural members of a suspension or outrigger scaffolds that provide support. [29 CFR 1926.450(b)] They must be placed perpendicular to their bearing support. [29 CFR 1926.451(d)(3)(viii)]
Where do tiebacks for outrigger beams, cornice hooks, roof hooks, roof irons, parapet clamps, or similar devices need to be secured?
Tiebacks must be secured to a structurally sound anchorage on the building or structure. Sound anchorages do not include standpipes, vents, other piping systems, or electrical conduit. [29 CFR 1926.451(d)(3)(ix) and 29 CFR 1926.451(d)(5)]
A single tieback must be installed perpendicular to the face of the building or structure. Two tie-backs installed at opposing angles are required when a perpendicular tieback cannot be installed. [29 CFR 1926.451(d)(3)(x)]
The suspension ropes must be long enough to allow the scaffold to be lowered to the level below without the rope passing through the hoist, or the end of the rope configured to prevent the end from passing through the hoist. [29 CFR 1926.451(d)(6)] Also see, OSHA Standards and Interpretation Letter: 06/16/1999 - Scaffolds: Lifelines, support lines, and suspension ropes cannot have a common anchor point.
The standard prohibits using repaired wire. [29 CFR 1926.451(d)(7)]
Drum hoists must contain no less than four wraps of the rope at the lowest point. [29 CFR 1926.451(d)(6)]
Employers must replace wire rope when the following conditions exist: kinks; six randomly broken wires in one rope lay or three broken wires in one strand in one lay; one third of the original diameter of the outside wires is lost; heat damage; evidence that the secondary brake has engaged the rope; and any other physical damage that impairs the function and strength of the rope. [29 CFR 1926.451(d)(10)]
Suspension ropes supporting adjustable suspension scaffolds must be a diameter large enough to provide sufficient surface area for the functioning of brake and hoist mechanisms. [29 CFR 1926.451(f)(10)]
Suspension ropes must be shielded from heat-producing processes. [29 CFR 1926.451(f)(11)]
Power-operated hoists used to raise or lower a suspended scaffold must be tested by a qualified testing laboratory. [29 CFR 1926.451(d)(13)]
The stall load of any scaffold hoist must not exceed three times its rated load. [29 CFR 1926.451(a)(5)]
The stall load is the load at which the prime-mover (motor or engine) of a power-operated hoist stalls or the power to the prime-mover is automatically disconnected. [29 CFR 1926.450(b)]
Gasoline power-operated hoists or equipment are not permitted. [29 CFR 1926.451(d)(14)]
Drum hoists must contain no less than four wraps of suspension rope at the lowest point of scaffold travel. [29 CFR 1926.451(d)(6)]
Gears and brakes must be enclosed. [29 CFR 1926.451(d)(15)]
An automatic braking and locking device, in addition to the operating brake, must engage when a hoist makes instantaneous change in momentum or an accelerated overspeed. [29 CFR 1926.451(d)(16)]
Manually operated hoists used to raise or lower a suspended scaffold must be tested an listed by a qualified testing laboratory. [29 CFR 1926.451(d)(13)]
These hoists require a positive crank force to descend. [29 CFR 1926.451(d)(17)]
Welding can be done from suspended scaffolds when
- a grounding conductor is connected from the scaffold to the structure and is at least the size of the welding lead.
- the grounding conductor is not attached in series with the welding process or the work piece.
- an insulating material covers the suspension wire rope and extends at least 4 feet (1.2 m) above the hoist.
- insulated protective covers cover the hoist.
- the tail line is guided, retained, or both, so that it does not become grounded.
- each suspension rope and any other independent lines are insulated from grounding. [29 CFR 1926.451(f)(17)]
What materials can be used to increase the working level height of employees on suspended scaffolds?
No materials or devices may be used to increase the working height on a suspension scaffold. This includes ladders, boxes, and barrels. [29 CFR 1926.451(f)(14) and 29 CFR 1926.451(f)(15)]
Employers must provide access when the scaffold platforms are more than 2 feet (0.6 m) above or below a point of access. [29 CFR 1926.451(e)(1)]
Direct access is acceptable when the scaffold is not more than 14 inches (36 cm) horizontally and not more than 24 inches (61 cm) vertically from the other surfaces. [29 CFR 1926.451(e)(8)]
The standard prohibits the use of crossbraces as a means of access. [29 CFR 1926.451(e)(1)]
Several types of access are permitted:
- Ladders, such as portable, hook-on, attachable, and stairway [29 CFR 1926.451(e)(2)]
- Stair towers [29 CFR 1926.451(e)(4)]
- Ramps and walkways [29 CFR 1926.451(e)(5)]
- Integral prefabricated frames [29 CFR 1926.451(e)(6)]
Effective September 2, 1997, employees erecting and dismantling supported scaffolding must have a safe means of access provided when a competent person has determined the feasibility and analyzed the site conditions. [29 CFR 1926.451(e)]
Shore and lean-to scaffolds are strictly prohibited. [29 CFR 1926.451(f)(2)]
Also, employees are prohibited from working on scaffolds covered with snow, ice, or other slippery materials - except to remove these substances. [29 CFR 1926.451(f)(8)]
The standard does require specific clearance distances. [29 CFR 1926.451(f)(6)]
Fall Protection Requirements
Employers must provide fall protection for each employee on a scaffold more than 10 feet (3.1 m) above a lower level. [29 CFR 1926.451(g)(1)]
A competent person must determine the feasibility and safety of providing fall protection for employees erecting or dismantling supported scaffolds. [29 CFR 1926.451(g)(2)]
Fall protection includes guardrail systems and personal fall arrest systems. Guardrail systems are explained below in another question. A personal fall-arrest system is a system used to arrest an employee in a fall from a working level. Personal fall-arrest systems include harnesses, components of the harness/belt such as D-rings, and snap hooks, lifelines, and anchorage points.
NOTE: As of January 1, 1998, subpart M of this part provides that body belts are not acceptable as part of a personal fall arrest system. [29 CFR 1926.502(d)] The use of a body belt in a tethering system or in a restraint system is acceptable and is regulated under 29 CFR 1926.502(e). [29 CFR 1926.453(b)(2)(v) and 29 CFR 1926.451(g)(3)]
Vertical or horizontal lifelines may be used. [29 CFR 1926.451(g)(3)(iii) and 29 CFR 1926.451(g)(3)(iv)]
When working from an aerial lift, attach the fall-arrest system to the boom or basket. [29 CFR 1926.453(b)(2)(v)]
The following chart illustrated the type of fall protection required for specific scaffolds.
|Type of Scaffold||Fall Protection Required|
|Aerial lifts||Personal fall-arrest system|
|Boatswains' chair||Personal fall-arrest system|
|Catenary scaffold||Personal fall-arrest system|
|Personal fall-arrest system, or a guardrail system, or a ¾ inch (1.9 cm) diameter grabline or equivalent handhold securely fastened beside each crawling board|
|Float scaffold||Personal fall-arrest system|
|Ladder jack scaffold||Personal fall-arrest system|
|Needle beam scaffold||Personal fall-arrest system|
|Self-contained scaffold||Both a personal fall-arrest system and a guardrail system|
|Single-point and two-point suspension scaffolds||Both a personal fall-arrest system and a guardrail system|
|Supported scaffold||Personal fall-arrest system or guardrail system|
|All other scaffolds not specified above||Personal fall-arrest system or guardrail systems that meet the required criteria|
Personal fall arrest systems can be used on scaffolding when there are no guardrail systems. [29 CFR 1926.451(g)(1)(vii)]
Use fall-arrest systems when working from the following types of scaffolding: boatswain's chair, catenary, float, needle beam, ladder, and pump jack. [29 CFR 1926.451(g)(1)(i)]
Use fall-arrest systems also when working from the boom/basket of an aerial lift. [29 CFR 1926.453(b)(2)(v)]
Fall-arrest and guardrail systems must be used when working on single- and two-point adjustable suspension scaffolds and self-contained adjustable scaffolds that are supported by ropes. [29 CFR 1926.451(g)(1)]
Falling Object Protection
To protect employees from falling hand tools, debris, and other small objects, install toeboards, screens, guardrail systems, debris nets, catch platforms, canopy structures, or barricades. In addition, employees must wear hard hats. [29 CFR 1926.451(h)(1), 29 CFR 1926.451(h)(2) and 29 CFR 1926.451(h)(3)]