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Course 804 - Safe Scaffold Erection and Inspection

Safety guides and audits to make your job as a safety professional easier

Inspecting Fabricated Frame Supported Scaffolds

supported scaffold
Supported scaffold examples
(Click to enlarge)

Introduction

Supported scaffolds consist of one or more platforms supported by outrigger beams, brackets, poles, legs, uprights, posts, frames, or similar rigid support. Because frame scaffolds are the most common type of supported scaffold, this course uses the Fabricated Frame Scaffold to describe requirements that are common to all supported scaffolds. Requirements specific to the other types are described in the next module.

Self-Supporting Scaffolds

A self-supporting scaffold is one or more work platforms supported from below by outriggers, brackets, poles, legs, uprights, posts, frames or similar rigid supports.

1. What is the most common type of supported scaffold?

a. Pole scaffolds
b. Frame supported scaffold
c. Shore or Lean-to scaffolds
d. Tube and Coupler scaffolds

Next Section

fab frame

Inspecting Fabricated Frame Scaffolds

Fabricated frame scaffolds are the most common type of scaffold because they are versatile, economical, and easy to use. They are frequently used in one or two tiers by residential contractors, painters, etc., but their modular frames can also be stacked several stories high for use on large-scale construction jobs.

Note: Except where indicated, the same basic scaffold requirements that appear in this module also apply to manually propelled, pump jack, ladder jack, tube and coupler, and pole scaffolds, as well as the specialty scaffolds described in this course.

Base Section

It is impossible for a stable structure to be built upon a foundation that does not start out square and level. OSHA has standards that apply specifically to the steps that must be taken to assure a stable scaffold base.

Real-Life Example

Scaffold Collapses and Worker Injured

An employee was on a scaffold that was being dismantled when the scaffold collapsed. He fell, sustaining a concussion for which he was hospitalized. The scaffold was not secured to wooden footing supports, nor was it tied to the building.

2. It is impossible for a stable scaffold structure to be built unless _____.

a. the base is wider than the top level
b. it contains vibration sensors
c. the foundation is square and level
d. it is attached to the building

Next Section

Inspecting Fabricated Frame Scaffolds (Continued)

Foundations

fab frame

Scaffolds are never as safe as the foundations they are built on. In order to assure scaffold stability, make sure:

  • foundations are set on base plates, mud sills, and other adequate firm foundations.
  • footings are capable of supporting the loaded scaffold without settling or displacement.
  • unstable objects are not used to support scaffolds or platform units.
  • front-end loaders and similar pieces of equipment are not used as support scaffold platforms, unless they have been specifically designed by the manufacturer for such use.
  • forklifts are not used to support scaffold platforms, unless:
    • the entire platform is attached to the fork; and
    • the forklift is not moved horizontally while the platform is occupied.

Note: One way to ensure a stable foundation when a sill is used is to secure it to the baseplate.

Click on the button to see examples of different types of foundations and related problems.

foundation
Poor foundation: Scaffold end frames, which have no base plate, are erected on top of scrap wood and unstable cement blocks.
(Click to enlarge)

Compacted Soils & Then Frozen - Compacted soils, as with all soils, swell and heave due to moisture content or water contained within the soil. This creates a dangerous situation during the freeze/thaw cycle (which can occur in the course of a day) causing the soil to swell or settle and may not result in a level rigid footing. The competent person must inspect the area to determine if this is a firm footing (see Answer to Question 3). Then this must be inspected when conditions change, such as sunny conditions, warming temperatures, etc.

Cold asphalt paving (winter) - Asphalt has minimal compressive strength, even when cold, and especially when applied. By itself it is not normally a useable foundation material.

Hot asphalt paving (summer) - This type of asphalt (top coat) is soft when placed and then compacted with rollers. It is generally applied as a thin coat over a base coat and takes several days to achieve its designed strength. Only the base coat gives the asphalt compressive strength.1

Wood decking - This may lend itself for use as a foundation. However, an evaluation of the deck for its maximum allowable loading would be required, since the decking or deck structure could fail under a full scaffold load. The competent person would need to know the individual scaffold base plate loading and if each one is below the maximum allowable deck loading. A light weight supported scaffold could be used on wood decking when the competent person has determined the structure would support the scaffold and its entire load.

Compacted Gravel Roads - This type of road surface may have adequate strength but the material does not provide a smooth surface. Additionally, there is no material cohesion; during a storm the material can wash away under the scaffold base plates.

3. What are supported scaffold foundations set on to ensure stability?

a. wet sand
b. loose, deep gravel
c. mud slopes
d. base plates

Next Section

Inspecting Fabricated Frame Scaffolds (Continued)

unstable
Scaffold is not level because it was erected without base plates on an uneven surface.
(Click to enlarge)

Scaffold Plumb

Supported scaffold poles, frames, uprights, etc. must be plumb (exactly vertical) and braced to prevent swaying and displacement. In general, a level is the easiest way to achieve the desired right angles.

Inspecting the Support Structure

To control the risk of a scaffold falling or collapsing, employers must assure that scaffolds are built within OSHA standards relating to strength and structural integrity.

Note: Except where indicated, these requirements also apply to manually propelled, pump jack, ladder jack, tube and coupler, and pole scaffolds, as well as the specialty scaffolds described in their applicable sections.

Capacity

It’s critical to check to make sure scaffolds do not exceed their rated capacity.

  • Check that scaffolds and scaffold components are capable of supporting, without failure, their own weight and at least 4 times their maximum intended load.
  • Ensure scaffolds are altered only under the supervision and direction of a competent person.

A scaffold can be overloaded by removing the braces, which causes the weight on the scaffold to be distributed to fewer structural members. Even if they are "in the way," braces should not be removed while work is being performed on a scaffold!

4. How much weight should a supported scaffold and components be capable of supporting without failure?

a. The scaffold's own weight
b. The scaffold's own weight and at least 2 times its maximum intended load
c. The scaffold's own weight and at least 4 times its maximum intended load
d. At least 3 times its maximum intended load

Next Section

Inspecting the Support Structure (Continued)

Bracing

capacity
Using wire to connect bracing is not safe.
capacity
Pins help to prevent scaffold collapse.

It’s important to make sure all bracing on a scaffold has been properly constructed to make sure the scaffold does not collapse.

  • Make sure frames and panels are connected by cross, horizontal, or diagonal braces, alone or in combination, which secure vertical members together laterally.
  • Check to make sure frames are stacked, and that cross braces are of such length as will automatically keep the scaffold plumb, level, and square.
  • Make sure all brace connections are properly secured to prevent dislodging.

Note: A level should be used during assembly to make sure new structural components remain in line.

Pinning

Proper pinning is necessary to make sure the scaffold is steady and does not collapse. Separation of frames can occur in high winds (uplift), or when workers climb endframes, overload the platform, or strike the scaffold with tools, materials, etc.

  • Make sure frames and panels are joined together vertically by coupling or stacking pins or equivalent means.
  • Ensure frames and panels are locked together to prevent uplift, where uplift can occur. Uplift is the separation of a frame from the frame below it.

5. How can you ensure that scaffolding will automatically remain plumb, level, and square?

a. Alternate the length of diagonal braces
b. Make sure lower braces are longer than upper braces
c. Install cross braces that are the appropriate length
d. Connect frames with vertical braces

Next Section

Inspecting the Support Structure (Continued)

Components

components
How can the components of this jury-rigged scaffold possess sufficient structural integrity?

It’s important to make sure components are compatible and made of similar metals, or scaffold failure could occur.

  • Make sure scaffold components manufactured by different manufacturers are not intermixed, unless they fit together without being forced and the scaffold's structural integrity is maintained.
  • Ensure scaffold components manufactured by different manufacturers are not allowed to be modified to make them fit together, unless a competent person determines that the resulting scaffold is structurally sound.
  • Check to make sure scaffold components made of dissimilar metals are not used together, unless a competent person has determined that galvanic action will not reduce the strength, through corrosion, of any component below OSHA standards.

6. Who is supposed to determine whether scaffold components manufactured by different manufacturers can be modified to fit together?

a. Experienced worker
b. A Competent person
c. A certified safety professional
d. On-site safety manager

Next Section

Inspecting for Adequate Access

Workers are most vulnerable to fall hazards when climbing on or off a scaffold. Therefore, employers are required to provide safe scaffold access.

Erectors and dismantlers face additional access problems due to the incomplete condition of the scaffolding. Requirements to prevent falls that apply only to these workers are addressed separately below.

The competent person is responsible for determining the safety and feasibility of installing and using safe means of access, based on site conditions and the type of scaffold involved.

  • Be sure employees are able to safely access any level of a scaffold that is 2 feet above or below an access point.
  • Make sure employees do not use cross-braces as a means of access.
supported scaffold

Real-Life Example

Improper Access Leads to Serious Injuries

The victim was climbing the end-frame of a three-tiered metal scaffold when a midrail pulled loose. He fell approximately 12 feet to a concrete dock. He suffered multiple fractures to the head, left and right foot, and left wrist, and torn ligaments in the knees.

7. When are workers on scaffolding most vulnerable to fall hazards?

a. When training new workers
b. When planning the construction of the scaffold
c. When working and properly connected to a fall harness
d. When climbing on or off a scaffold

Next Section

Ladders

ladder

The most frequent fall-from-elevation accident is a fall off ladders. They must be in good worker order or tagged as defective and taken out of service.

  • Make sure portable, hook-on, and attachable ladders are positioned so as not to tip the scaffold.
  • Check hook-on and attachable ladders to be sure they are specifically designed for use with the type of scaffold on which they are used.
  • Make sure hook-on and attachable ladder rungs:
    • are positioned so that their bottom rung is not more than 24 inches above the scaffold supporting level;
    • have uniform spacing between rungs of a maximum 16¾ inches;
    • have minimum rung length of 11½ inches; and
    • have rest platforms provided at a maximum of 35-foot vertical intervals
  • Ensure stairway-type ladders:
    • are positioned so that their bottom step is not more than 24 inches above the scaffold supporting level;
    • have rest platforms at maximum vertical intervals of 12 feet;
    • have a minimum step width of 16 inches, except for mobile scaffold stairway-type ladders, which must have a minimum step width of 11½ inches; and
    • have slip-resistant treads on all steps and landings
  • Check that steps and rungs of ladders and stairway-type ladders line up vertically with each other between rest platforms.

8. What do you need to do with a ladder that is defective?

a. Tag it and take it out of service
b. Put it on a review list for evaluation and possible removal
c. Use it "carefully" until the company can afford a new ladder
d. Nothing, just ignore it because it's likely no one will be hurt

Next Section

ladder

Ladders (Continued)

Integral (Built-in ladder) Frames

Make sure integral (built-in ladder) scaffold access frames:

  • are specifically designed and constructed for use as ladder rungs
  • are not used as work platforms when rungs are less than 11½ inches in length, unless each affected employee uses appropriate fall protection
  • have rungs which are uniformly spaced and a length of at least 8 inches, with a maximum space between rungs of 16¾ inches
  • have rest platforms provided at a maximum of 35 foot vertical intervals

Ladders on Stair Towers

Stair towers have many specific design requirements.

Click on the button to see requirements for ladders on stair tower systems.

Make sure stair towers have:

stairs
  • a stair rail consisting of a toprail and a midrail on each side of the stairway
  • a toprail of each stair rail system capable of serving as a handrail, unless a separate handrail is provided
  • sufficient handhold on handrails, and toprails serving as handrails, for employees grasping them to avoid falling
  • stair rails and handrails surfaced to prevent punctures or lacerations to employees, and to prevent snagging of clothing
  • stair rails and handrails constructed so that they do not constitute a projection hazard
  • a space of at least 3 inches between handrails, or stair rails used as handrails, and other objects
  • a distance of no less than 28 inches and no more than 37 inches from the upper surface of the stair rail to the forward edge of the tread, in line with the face of the riser
  • a landing platform at least 18 inches wide by 18 inches long at each level
  • a scaffold stairway width of at least 18 inches between stair rails
  • slip-resistant surfaces on treads and landings
  • stairways installed between 40 degrees and 60 degrees from the horizontal
  • guardrails meeting OSHA requirements on the open sides and ends of each landing
  • uniform riser height, within ¼-inch, for each flight of stairs
  • greater variations in riser height are allowed for the top and bottom steps of the entire system (not for each flight of stairs)
  • uniform tread depth, within ¼-inch, for each flight of stairs

9. What are integral (built-in) access frames specifically designed for?

a. Dismantling scaffolding
b. Temporary scaffolding
c. Single-level scaffolding
d. Use as ladder rungs

Next Section

fab scaffold

Ramps and Walkways

  • Ensure ramps and walkways 6 feet or more above lower levels have guardrails that comply with 1926 Subpart M - Fall Protection.
  • Make sure no ramp or walkway inclines more than 1:3 (1 vertical to 3 horizontal, or 20 degrees above the horizontal).
  • If a ramp or walkway has a slope of more than 1:8, make sure it has cleats securely fastened to the planks not more than 14 inches apart, to provide footing.

Direct Access

Check that direct access to or from another surface is permitted only when the scaffold is not more than 14 inches horizontally and not more than 24 inches vertically from the other surface.

Erectors and Dismantlers

  • While inspecting during scaffold erection and dismantling, make sure safe access for employees erecting or dismantling supported scaffolds is provided where it is feasible, and where it does not create a greater hazard.
  • Ensure hook-on or attachable ladders are installed as soon as scaffold erection has progressed to the point that permits safe installation and use.
  • When erecting and dismantling tubular, welded-frame scaffolds, and end frames are used as climbing devices for access, make sure:
    • Horizontal members are parallel, level, and not more than 22 vertical inches apart.
    • Horizontal members are erected in a manner that creates a usable ladder and provides good hand hold and foot space.
  • Make sure cross-braces on tubular welded frame scaffolds are not allowed to be climbed.

10. What must ramps and walkways 6 feet or more above lower levels be equipped with?

a. Vertical walls
b. Fall harnesses
c. Guardrails
d. Hatchways

Next Section

Inspecting for Fall Protection

The number one scaffold hazard is worker falls. Fall protection consists of either personal fall-arrest systems or guardrail systems, and must be provided on any scaffold 10 feet or more above a lower level. Specific requirements are described below.

Note: Except where indicated, these requirements also apply to manually propelled, pump jack, ladder jack, tube and coupler, and pole scaffolds, as well as the specialty scaffolds.

  • Ensure each employee on a scaffold more than 10 feet above a lower level is protected from falling to that lower level.
  • Ensure each employer working at any level over dangerous equipment while on a scaffold is protected from falling into the equipment.
  • Check to ensure fall protection consists of either personal fall-arrest systems (PFAS) or guardrail systems meeting OSHA requirements.
  • Ensure that employees performing overhand bricklaying operations from a supported scaffold are protected from falling from all open sides and ends of the scaffold, except at the side next to the wall being laid.
platform

Fall-Arrest Systems

Personal fall arrest systems can be used on scaffolding when there are no guardrail systems. Personal fall-arrest systems used on scaffolds should be attached by lanyard to a vertical lifeline, horizontal lifeline, or scaffold structural member.

  • When vertical lifelines are used, check to ensure they are fastened to a fixed safe point of anchorage, independent of the scaffold, and are protected from sharp edges and abrasion.
  • Check to ensure safe points of anchorage, such as structural members of buildings, are being used.
  • Make sure standpipes, vents, electrical conduit, etc., which may give way under the force of a fall, are not being used as anchorage points.
  • Make sure two or more vertical lifelines are not attached to each other, or to the same point of anchorage.
  • When horizontal lifelines are used, make sure they are being secured to two or more structural members of the scaffold.

Real-Life Example

Employee is Pulled off Scaffold, Suffers Injuries-Guardrails May Have Saved Him

While sitting or kneeling on a fixed deck plank attached to a fabricated frame scaffold, a worker was pulling a 16-foot long 2x4 off the bucket of an excavator. There were no guardrails at the working level. When the other end of the 2x4 slipped off the bucket, the employee did not let go of his end, and was pulled off the deck. He fell 16 feet to the ground, sustaining facial fractures and other injuries.

11. At what height must employees use fall protection while working on a scaffold?

a. Four or more feet above ground level
b. Six feet while working above dangerous equipment
c. Ten feet or more above a lower level
d. More than 15 feet above a lower level

Next Section

Guardrail Systems

components
This scaffold has no guardrails and is not fully planked.

Guardrail systems — or guardrails — are barriers erected along an unprotected or exposed side or edge of a walking-working surface to prevent falls. 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. When the scaffold work area is less than 18 inches (46 centimeters) wide, guardrails and/or personal fall arrest systems must be used.

  • Height: The height of the toprail for scaffolds manufactured and placed in service after January 1, 2000 must be between 38 inches (0.9 meters) and 45 inches (1.2 meters). The height of the toprail for scaffolds manufactured and placed in service before January 1, 2000 can be between 36 inches (0.9 meters) and 45 inches (1.2 meters).
  • Placement: 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.
  • Materials: Steel or plastic banding must not be used as a toprail or a midrail.
  • Strength:
    • Guardrail systems must be capable of withstanding, without failure, a force of at least 200 pounds applied in a downward or outward direction at any point within two inches of the top edge of the top rail. The guardrail system must not deflect to a height less than 39 inches.
    • Manila or synthetic rope used for top rails must be inspected to ensure that the rope meets the strength requirement.
    • Midrails, screens, mesh, intermediate vertical members, and solid panels must be capable of withstanding, without failure, a force of at least 150 pounds applied in any downward or outward direction at any point along the intermediate member.
    • Manila or synthetic rope used for midrails must be inspected to ensure that the rope meets the strength requirement.
  • Midrails: Midrails must be installed approximately halfway between the toprail and the platform surface. When a crosspoint of crossbracing is used as a midrail, it must be between 20 inches (0.5 meters) and 30 inches (0.8 m) above the work platform.
  • Crossbracing: When the crosspoint of crossbracing is used as a toprail, it must be between 38 inches (0.97 m) and 48 inches (1.3 meters) above the work platform.
  • Screens and mesh: When used, must extend from the walking-working surface to the top rail and along the entire opening between top-rail supports.
  • Intermediate vertical members: Must be installed no more than 19 inches apart.
  • Surfaces: Guardrail systems must have smooth surfaces.
  • Ends of top rails and midrails: Must not pose a projection hazard.
  • Steel or plastic banding: Must not be used for top rails or midrails. Chain or cables can be used when they satisfy all of the guardrail requirements.
  • Top rail and midrail dimensions: Must be at least 0.25 inches in diameter or 0.25 inches thick.
  • Guardrail systems used at hoist areas: A removable guardrail section, consisting of a top rail and midrail, must be placed across the access opening between guardrail sections when the hoist is not being used. Chains or gates are acceptable if they offer equivalent protection.
  • Use of Stilts: Stilts may be used by employees 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.
  • Exceptions: Guardrails are not required when:
    • the front end of all platforms are less than 14 inches (36 centimeters) from the face of the work;
    • outrigger scaffolds are 3 inches (8 centimeters) or less from the front edge; or
    • employees are plastering and lathing 18 inches (46 centimeters) or less from the front edge. )

12. Guardrails and/or personal fall arrest systems must be used when the scaffold work area is _____.

a. less than 18 inches wide
b. more than 18 inches wide
c. less than 12 inches wide
d. more than 12 inches wide

Next Section

Inspecting the Platform

Except when used only as a walkway, the platform is the work area of the scaffold. Therefore, an inspection of a scaffold platform requires safety checks of both the platform structure and how the platform is used by the workers.

Planking

gaps
The platform gaps are too wide. The spaces between platforms cannot exceed one inch.
  • Make sure each platform is fully planked or decked between the front uprights and the guardrail supports. Note: Platforms used solely as walkways, or during erection or dismantling, require only the planking that the employer establishes is necessary to provide safe working conditions.
  • Make sure no gaps greater than 1 inch are permitted between adjacent planks or deck units, or between the platform and the uprights.
  • If it can be demonstrated that a wider space is necessary, check to make sure the gap is as small as possible and does not exceed 9 1/2 inches.
  • Ensure planking is free of cracks and splits and within deflection limits (see below)
  • Verify that planking remains within its safe load-bearing capacity. Make sure the planks are not allowed deflect more than 1/60th of its span between supports. A competent person should monitor deflection.
  • components
    This scaffold is overloaded and planks are strained.
  • Make sure wooden planking is covered with opaque finishes, except that platform edges may be marked for identification. Note: Platforms may be coated periodically with wood preservatives, fire retardants, and slip-resistant finishes, provided they do not obscure the top or bottom wood surfaces.
  • Ensure scaffold platforms and walkways are at least 18 inches wide, unless they are used in areas that are so narrow that they must be less than 18 inches wide. In such cases, verify that the platforms are as wide as feasible, and fall protection is provided.
  • Make sure that anything that could cause a slip, trip or fall (i.e. tools, scrap material, chemicals, snow, ice, etc.) has not been allowed to accumulate on the platform. Note: For the same reason, cleats or other means of connecting planks should be on the underside.
  • Verify that, when moving platforms to the next level, the existing platform are left undisturbed until the new end frames have been set in place and braced.

13. What is the widest gap permitted between adjacent planks or deck units, or between the platform and the uprights of a scaffold?

a. No gaps permitted
b. No more than 1 inch
c. No more than 2 inches
d. No more than 3 inches

Check your Work

Read the material in each section to find the correct answer to each quiz question. After answering all the questions, click on the "Check Quiz Answers" button to grade your quiz and see your score. You will receive a message if you forgot to answer one of the questions. After clicking the button, the questions you missed will be listed below. You can correct any missed questions and check your answers again.

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