Skip Navigation

Course 804 - Safe Scaffold Erection and Inspection

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

Inspecting Other Supported Scaffolds

tube coupler
Tube and coupler scaffolds
(Click to enlarge)

Inspecting Tube and Coupler Scaffolds

A tube and coupler scaffold is a supported scaffold consisting of platforms supported by individual pieces of tubing, erected with coupling devices connecting uprights, braces, bearers and runners.

Tube and coupler scaffolds more than 125 feet high must be designed by a registered professional engineer and constructed and loaded consistent with the design.


Braces are rigid connections that hold one scaffold member in a fixed position with respect to another member, or to a building or structure.

  • Check that transverse bracing forming an "X" across the width of the scaffold is installed at the scaffold ends and at least at every third set of posts horizontally (measured from only one end) and every fourth runner vertically.
  • Ensure bracing extends diagonally from the inner or outer posts or runners upward to the next outer or inner posts or runners.
  • Check that building ties are installed at the bearer levels between the transverse bracing and conform to the requirements of 1926.451(c)(1).
  • Make sure bracing is placed for each section of six levels between the fourth and sixth levels.
  • Ensure bracing extends diagonally from the inner or outer posts or runners at the bottom of the fourth level, upward to the inner or outer posts or runners at the bottom of the fifth level, and likewise to the sixth level.
  • If this technique is used, check that the scaffold is tied at the "k" function level.
  • Check that on straight run scaffolds, longitudinal/diagonal bracing across the inner and outer rows of posts is installed diagonally in both directions and extends from the base of the end posts upward to the top of the scaffold at approximately a 45-degree angle.
  • When the length of the scaffold is greater than the height, bracing should be repeated starting at least with every fifth post.
  • When the length is shorter than the height, bracing should be installed from the base of end posts upward to the opposite end posts and then in alternating directions until the top of the scaffold is reached.
  • In situations where the attachment of bracing to posts is precluded, the bracing should be attached to the runners.

1. At what height must tube and coupler scaffolds be designed by a registered professional engineer?

a. More than 75 feet high
b. Between 100 and 150 feet high
c. More than 125 feet high
d. All heights above 100 feet

Next Section

Inspecting Tube and Coupler Scaffolds (Continued)

(Click to enlarge)


Bearers (putlogs) are horizontal transverse scaffold members (which may be supported by ledgers or runners) upon which the scaffold platform rests and which joins scaffold uprights, posts, poles, and similar members.

  • Bearers should be installed transversely between the posts, and when coupled to the posts, the inboard coupler should bear directly on the runner coupler.
  • When the bearers are coupled to the runners, the couplers should be as close to the posts as possible.
  • Bearers should extend beyond the posts and runners and provide full contact with the coupler.
  • When platforms are being moved to the next level, verify that the existing platform is left undisturbed until new bearers have been set in place and braced prior to receiving the new platforms.


Runners (ledgers or ribbons) are the lengthwise horizontal spacing or bracing members which may support the bearers.

  • The scaffold should have runners installed along its entire length and along both the inside and outside posts at the various level heights.
  • Runners should be interlocked on straight runs to create continuous lengths and be coupled to each post.
  • Bottom runners should be located as close to the base as possible. Couplers should be made of structural metal.

Improper Coupling Results in Two Deaths

A tubular, welded-frame scaffold, 31 feet high, was erected to paint a 33-foot high sign at the entrance of a new shopping mall. After the sign had been partially painted, the scaffold was moved to allow concrete to be placed around the sign. Several days later, a crew of seven workers was instructed to replace the scaffold and finish painting the sign. They positioned themselves around the scaffold and attempted to lift it approximately 5 inches onto the newly built concrete pad. As they were lifting the scaffold, the top section partially separated from the adjoining section, toppled over, and contacted a power line. A 28-year old carpenter and a 31-year old laborer were electrocuted. The other five workers were hospitalized with electrical burns.

2. The lengthwise horizontal spacing or bracing members a tube and coupler scaffold are called _____.

a. bearers
b. runners
c. sills
d. bracing

Next Section

Mobile Scaffolds

mobile scaffold
Two workers were injured working on a mobile scaffold with unlocked casters.
(Click to enlarge)

A mobile scaffold is a powered or non-powered, portable, caster or wheel-mounted supported scaffold. Mobile scaffolds constructed of tube and coupler components or of fabricated frames should conform to design, construction and loading requirements for those scaffolds.

  • Ensure scaffolds are braced by cross, horizontal or diagonal braces, or combination thereof, to prevent racking or collapse, and that vertical members are secured together laterally so that vertical members are squared and aligned.
  • Make sure scaffolds are plumb, level and squared and that all brace connections are secured.
  • Make sure caster and wheel stems are pinned or otherwise secured in scaffold legs.
  • Ensure platforms do not extend past the base supports unless outrigger frames or equivalent devices are used to ensure stability.
  • mobile scaffold

  • Make sure that, while in a stationary position, casters and wheels are locked with a positive wheel and/or wheel and swivel locks, or equivalent means, to prevent movement. Note: A rolling scaffold load capacity is limited by the weight its casters can support.
  • Check that employees are not allowed to ride on a mobile scaffold unless strict controls are followed (level and unobstructed surfaces, a height ratio to width of not more than two to one, slow speed of movement, confinement of employees within the scaffold frame, etc.)
  • When manual force is used to move the scaffold, make sure the force is applied as close to the base as practicable, but no more than 5 feet above the supporting surface (i.e., scaffold base or wheels when a powered system is used).
  • Make sure powered systems used to propel mobile scaffolds are designed for such use.
  • Ensure forklifts, trucks, similar motor vehicles or add-on motors are not used to propel scaffolds unless the scaffold is designed for such propulsion systems.

3. Check to verify platforms on mobile scaffolds do not extend past the base supports _____.

a. except when they are tied to the frame
b. more than six inches on ends
c. at any time after installation
d. unless outrigger frames are used

Next Section

Inspecting Pole Scaffolds

Single Pole Scaffold

Pole scaffolds are a type of supported scaffold in which every structural component, from uprights to braces to platforms, is made of wood. Because they have to be built from scratch and cannot easily be reused, pole scaffolds are considered old-fashioned and are rarely used today.

Single Pole Scaffold. A single pole scaffold is a supported scaffold consisting of platforms resting on bearers, the outside ends of which are supported on runners (ledgers or ribbons) secured to a single row of posts or uprights, and the inner ends of which are supported on or in a structure or building wall.

Double Pole Scaffold. A double pole (independent pole) scaffold is a supported scaffold consisting of platforms resting on cross beams supported by ledgers and a double row of uprights independent of support (except for ties, guys and braces) from any structure.

Specific Requirements

Double Pole Scaffold
  • When platforms are moved to the next level, the existing platform must be left undisturbed until the new bearers have been set in place and braced.
  • Where wooden poles are spliced, the following regulations apply:
    • The ends must be squared.
    • The upper section must rest squarely on the lower section.
    • Wood splice plates or scab plates must be provided on at least two adjacent sides, and must:
      • Extend at least 2 feet on either side of the splice.
      • Overlap the abutted ends equally.
      • Have at least the same cross-sectional areas as the pole.
    • Splice plates made of materials other than wood may be used, as long as they are of equivalent strength.
  • Pole scaffolds over 60 feet in height must:
    • Be designed by a registered professional engineer.
    • Be constructed and loaded in accordance with that design.

4. Which of the following is TRUE regarding pole scaffolds?

a. They must be built from scratch
b. They are easy to reuse
c. They are commonly used today
d. They are made entirely of metal

Next Section

Inspecting Pole Scaffold (Continued)

Pole scaffolds more than 60 feet in height must be designed by a registered professional engineer and constructed and loaded in accordance with that design.

Inspecting Braces, Bearers, and Runners

  • Crossbracing must be installed between the inner and outer sets of poles on double pole scaffolds.
  • Diagonal bracing must be installed in both directions across:
    • The entire outside face of double- and single-pole scaffolds.
    • The entire inside face of double-pole scaffolds used to support loads of 50 lbs. or more per square foot.
  • Runners and bearers must be installed on edge.
  • Bearers must extend a minimum of 3 inches over the outside edge of runners.
  • Runners must:
    • Extend over two poles at minimum.
    • Be supported by bearing blocks securely attached to the poles.
  • Braces, bearers, and runners must not be spliced between poles.

5. At what height must pole scaffolds be designed by a registered professional engineer?

a. Any height above 10 feet for single-pole scaffolds
b. Any height over 30 feet for double-pole scaffolds
c. More than 60 feet in height
d. More than 125 feet in height

Next Section

Bricklayer’s Square


A bricklayer’s square scaffold is a supported scaffold composed of framed squares that support a platform.

  • Ensure these types scaffolds do not exceed three tiers in height and are constructed and arranged so that one square rests directly above the other.
  • Make sure scaffolds made of wood are reinforced with gussets on both sides of each corner.
  • Check that diagonal braces are installed between squares on the rear and front sides of the scaffold and that they extend from the bottom of each square to the top of the next square.
  • Make sure the upper tiers of the scaffold stand on a continuous row of planks laid across the next lower tier and nailed down or otherwise secured to prevent displacement.

6. What is the maximum number of tiers a bricklayer's scaffold can have?

a. 2
b. 3
c. 4
d. 5

Next Section

Scissor Lifts

Scissor Lift
Aerial and Scissor Lifts.

Scissor lifts are mobile supported scaffold work platforms used to safely move workers vertically and to different locations in a variety of industries including construction, retail, entertainment and manufacturing. Scissor lifts move the work platform straight up and down using crossed beams functioning in a scissor-like fashion.

Although scissor lifts present hazards similar to scaffolding when extended and stationary, using scissor lifts safely depends on considering equipment capabilities, limitations and safe practices.

Click on the buttons below to see inspection items.

Inspection Items

When inspecting scissor lifts, check the following to make sure the scissor lift:

  • components are in proper working condition and not defective in any way;
  • brakes, once set, hold the scissor lift in position;
  • guardrails are installed before working on the lift to prevent workers from falling;
  • never moves in an elevated position;
  • is positioned so that work is within easy reach to avoid leaning away from the scissor lift;
  • is stable and will not tip over or collapse;
  • is positioned on firm, level surfaces away from hazards that can cause instability;
  • is isolated from other equipment that could contact it; and
  • is used outside only when weather conditions are good with wind speeds below 28 miles per hour.

The following work practices ensure that scissor lifts are used safely. Workers must:

  • only stand on the work platform; never stand on the guardrails;
  • never load the work platform beyond manufacturer's load rating;
  • only use the scissor lift mechanism to raise the work platform;
  • prevent the scissor lift from being struck by other equipment;
  • never move the scissor lift within 10 feet of energized or other overhead objects;
  • receive training on scissor lift safe use, identifying hazards, and reporting defects;
  • be receive electrical training to be qualified to work near electrical sources; and
  • use appropriate traffic control measures to prevent collision.

7. Which of the following is TRUE regarding scissor lift scaffolds?

a. They must not extend higher than 20 feet
b. The brakes must not be set when the scaffold lowered
c. They must never be moved in an elevated position
d. They may be used outside in winds up to 45 mph

Next Section

Aerial Lifts

Scissor Lift
Articulating (jointed) boom platform.

An aerial lift is any vehicle-mounted device used to elevate personnel. Types include:

  • Extendable boom platforms,
  • Aerial ladders,
  • Articulating (jointed) boom platforms,
  • Vertical towers, and
  • Any combination of the above.

Aerial lifts have replaced ladders and scaffolding on many job sites due to their mobility and flexibility. They may be made of metal, fiberglass reinforced plastic, or other materials. They may be powered or manually operated, and are considered to be aerial lifts whether or not they can rotate around a primarily vertical axis.

Many workers are injured or killed on aerial lifts each year. OSHA provides the following information to help employers and workers recognize and avoid safety hazards they may encounter when they use aerial lifts.

Inspecting the Lift

When inspecting aerial lifts, check the following pre-start, vehicle, lift, and guardrail system items:

Pre-start Inspection

Prior to each work shift, conduct a pre-start inspection to verify that the equipment and all its components are in safe operating condition. Follow the manufacturer’s recommendations and include a check of:

Vehicle components

  • proper fluid levels (oil, hydraulic, fuel and coolant);
  • leaks of fluids;
  • wheels and tires;
  • battery and charger;
  • lower-level controls;
  • horn, gauges, lights and backup alarms; and
  • steering and brakes.

Lift components

  • operating and emergency controls;
  • personal protective devices;
  • hydraulic, air, pneumatic, fuel and electrical systems;
  • fiberglass and other insulating components;
  • missing or unreadable placards, warnings, or operational, instructional and control markings;
  • mechanical fasteners and locking pins;
  • cable and wiring harnesses;
  • outriggers, stabilizers and other structures; and
  • loose or missing parts;

Guardrail systems

  • Do not operate any aerial lift if any of these components are defective until it is repaired by a qualified person.
  • Remove defective aerial lifts from service (tag out) until repairs are made.

Work Area Inspections

Employers must assure that work areas are inspected for hazards and take corrective actions to eliminate such hazards before and during operation of an aerial lift. Items to look for include:

  • drop-offs, holes, or unstable surfaces such as loose dirt;
  • inadequate ceiling heights;
  • slopes, ditches, or bumps;
  • debris and floor obstructions;
  • overhead electric power lines and communication cables;
  • other overhead obstructions;
  • other hazardous locations and atmospheres;
  • high wind and other severe weather conditions, such as ice; and
  • the presence of others in close proximity to the work.

Only trained and authorized persons are allowed to operate an aerial lift. The following training is required to ensure that aerial lifts are safely used:

  • Explanations of electrical, fall, struck-by and falling object hazards;
  • Procedures for dealing with hazards;
  • Recognizing and avoiding unsafe conditions in the work setting;
  • Instructions for correct operation of the lift (including maximum intended load and load capacity);
  • Demonstrations of the skills and knowledge needed to operate an aerial lift before operating it on the job;
  • When and how to perform inspections; and
  • Manufacturer’s requirements.

Workers should be retrained if any of the following conditions occur:

  • An incident occurs during aerial lift use,
  • Workplace hazards involving an aerial lift are discovered, or
  • A different type of aerial lift is used.
  • Employers should also retrain workers who they observe operating an aerial lift improperly.

8. Which vehicle-mounted device has replaced ladders and scaffolding on many job sites due to their mobility and flexibility?

a. Pneumatic lift
b. Hydraulic lift
c. Aerial lift
d. Scissor lift

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.

Next Module