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.

A registered professional engineer may need to be consulted about the design, construction, and loading of the scaffold.

  1. Verify tube and coupler scaffolds more than 125 feet high are designed by a registered professional engineer and constructed and loaded consistent with the design.
  2. Inspecting bracing
    1. 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.
    2. Ensure bracing extends diagonally from the inner or outer posts or runners upward to the next outer or inner posts or runners.
    3. Check that building ties are installed at the bearer levels between the transverse bracing and conform to the requirements of 1926.451(c)(1).
    4. Make sure bracing is placed for each section of six levels between the fourth and sixth levels.
    5. 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.
    6. If this technique is used, check that the scaffold is tied at the “k” function level.
    7. 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.
    8. When the length of the scaffold is greater than the height, such bracing should be repeated starting at least with every fifth post.
    9. When the length is shorter than the height, such 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.
    10. In situations where the attachment of bracing to posts is precluded, the bracing should be attached to the runners.

Inspecting Tube and Coupler Scaffolds (Continued)

guardrail
(Click to enlarge)
  1. Inspecting bearers
    1. Bearers should be installed transversely between the posts, and when coupled to the posts, the inboard coupler should bear directly on the runner coupler.
    2. When the bearers are coupled to the runners, the couplers should be as close to the posts as possible.
    3. Bearers should extend beyond the posts and runners and provide full contact with the coupler.
  1. Inspecting runners
    1. The scaffold should have runners installed along its entire length and along both the inside and outside posts at the various level heights.
    2. Runners should be interlocked on straight runs to create continuous lengths and be coupled to each post.
    3. Bottom runners should be located as close to the base as possible. Couplers should be made of structural metal.
  1. Verify that when platforms are being moved to the next level, the existing platform is left undisturbed until new bearers have been set in place and braced prior to receiving the new platforms.

Real-Life Example

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.

Mobile Scaffolds

mobile scaffold
The mobile scaffold in this image is over a 10-foot pit. There is a fall hazard of 16 feet to the lower level. There are also tools that may cause a tripping hazard as well as an improper climbing method.
(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.

  1. 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.
  2. Make sure scaffolds should be plumb, level and squared and that all brace connections are secured.
  3. Ensure platforms do not extend past the base supports unless outrigger frames or equivalent devices are used to ensure stability.
  4. Check to see that platforms do not extend past the base supports unless outrigger frames are used.
  5. Make sure caster and wheel stems are pinned or otherwise secured in scaffold legs.
  6. mobile scaffold
    Two workers were injured working on a mobile scaffold with unlocked casters. One of the casters came off when it hit a floor hole and the scaffold tipped over. The workers were lucky: they lived.
    (Click to enlarge)
  7. 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.
  8. 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.)
  9. 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).
  10. Make sure powered systems used to propel mobile scaffolds are designed for such use.
  11. 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.

Pole Scaffolds

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.

singlepole
Single Pole Scaffold
components
Double Pole Scaffold

Double Pole Scaffold (Continued)

  1. On double pole scaffolds, make sure crossbracing is installed between the inner and outer sets of poles.
  2. Make sure diagonal bracing in both directions are installed across the entire outside face of double pole scaffolds used to support loads equivalent to a uniformly distributed load of 50 pounds or more per square foot.
  3. On both double and single pole scaffolds, ensure diagonal bracing is installed across the entire outside face.
  4. Ensure runners and bearers are installed on the edges (e.g., narrow side on a two-by-four, the edge would be the 2-inch side).
    1. Bearers should extend a maximum of 3 inches over the outside edges of runners.
    2. Runners should extend over a minimum of two poles and be supported by bearing blocks securely attached to the poles.
    3. Braces, bearers and runners cannot be spliced between poles.
    4. Where wooden poles are spliced, the ends should be squared and the upper sections should rest squarely on the lower sections.
  1. When platforms are being moved to the next level, make sure the existing platforms are left undisturbed until the new bearers have been set in place and braced, prior to receiving the new platforms.
  2. Make sure pole scaffolds more than 60 feet in height are designed by a registered professional engineer and constructed and loaded in accordance with that design.

Bricklayer’s Square

bricklayer

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

  1. 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.
  2. Make sure scaffolds made of wood are reinforced with gussets on both sides of each corner.
  3. 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.
  4. 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.

Instructions

Before beginning this quiz, we highly recommend you review the module material. This quiz is designed to allow you to self-check your comprehension of the module content, but only focuses on key concepts and ideas.

Read each question carefully. Select the best answer, even if more than one answer seems possible. When done, click on the "Get Quiz Answers" button. If you do not answer all the questions, you will receive an error message.

Good luck!

1. Tube and coupler scaffolds more than _____ high should be designed by a registered professional engineer.

2. When the length of tube and coupler scaffolds is greater than the height, longitudinal bracing should be repeated at least every _____.

3. When inspecting mobile scaffolds, make sure that, while in a stationary position, _____ to prevent movement.

4. When manual force is used to move a mobile scaffold, make sure the force is applied _____, but not more than 5 feet above the supporting surface.

5. What is the maximum number of tiers allowed for Bricklayer's Square type scaffolds?


Have a great day!

Important! You will receive an "error" message unless all questions are answered.