Scaffolding Basics

Introduction

When scaffolds are not erected or used properly, fall hazards can occur. About 2.3 million construction workers frequently work on scaffolds. Protecting these workers from scaffold-related accidents would prevent an estimated 4,500 injuries and 50 fatalities each year.

Real-Life Scenario

On October 12, 1993, a 53-year-old male mason was fatally injured when he fell approximately twelve feet from the second level of an unguarded tubular welded scaffold system. It is not known what the victim was doing at the time of the incident; however, a witness saw him walk to the edge of the scaffold and place his foot on a piece of iron scaffold bracing. He either tripped or lost his balance, and fell to the sand covered asphalt below. The victim was transported to the local hospital where he died approximately two hours later.

Investigators concluded that in order to prevent similar future occurrences, employers should:

1. Install guardrails on all open sides of scaffolds which are more than ten feet above ground.

2. Ensure that scaffolding is properly erected, maintained, moved, dismantled and/or altered only under the supervision of a competent person.

3. Develop and implement a comprehensive safety program that includes, but is not limited to, training in fall hazard recognition and the use of fall protection devices.

What is a Scaffold?

A scaffold is defined as an elevated, temporary work platform. There are three basic types of scaffolds:

1. Supported scaffolds, which consist of one or more platforms supported by rigid, load- bearing members, such as poles, legs, frames, outriggers, etc.
2. Suspended scaffolds, which are one or more platforms suspended by ropes or other non-rigid, overhead support.
3. Other scaffolds, principally man lifts, personnel hoists, etc., which are sometimes thought of as vehicles or machinery, but can be regarded as another type of supported scaffold.

Scaffolding Terms

It’s important to know some of the common terms when dealing with scaffolding. For example, when an employee goes from one job site to another, knowing the proper scaffolding terms will improve communications and safety.

Here are the definitions for the most common terms, according to ANSI/ASSE A10.8-2011:

• Anchorage: A secure point of attachment for lifelines, lanyard, deceleration devices or tiebacks.
• Base Plate: A device used to distribute vertical load.
• Bearer: A horizontal member of a scaffold upon which the platform unit rests and that may be supported by runners.
• Boatswains’ Chair: A suspended seat designed to accommodate one worker in a sitting position.
• Body Harness, Full: Straps that are secured about an employee in a manner that distributes the arresting forces over at least the thighs, shoulders and pelvis with provisions for attaching a lanyard, lifeline or deceleration device.
• Brace: A device that holds one scaffold member in a fixed position with respect to another member.
• Competent Person: One who is capable of identifying existing and predictable hazards in the surroundings or working conditions that are unsanitary, hazardous or dangerous to employees, and who has the authority to take prompt corrective measures to eliminate such hazards.
• Crossbraces: Two diagonal scaffold members joined at their center to form an “X.” Used between frames or uprights or both
• Design Load: The maximum intended load; that is, the total of all loads including the worker(s), material and the equipment placed on the unit.

Scaffolding Terms (Continued)

Fall Protection Harness

• Electrical Ground: A conducting connection between an electrical circuit or equipment and the area, or some conducting body that serves in place of the earth.
• Fall Protection: A system designed to prevent or arrest a person’s fall.
• Guardrail System: A rail system erected along the open sides and ends of platforms. The rail system consists of a toprail and midrail and their supports.
• Guy: A rope, chain or cable used to stabilize a vertical object.
• Hoist: A device intended to be used to raise and lower a suspended scaffold. It may be either manually operated or power-operated.
• Lanyard: A flexible line to secure the wearer of a full body harness to a lifeline, trolley line or a fixed anchor.
• Maximum Intended Load: The total load of all workers, equipment, tools and materials.
• Midrail: A rail approximately midway between the toprail and platform of a guardrail system.
• Open Sides and Ends: That portion of a scaffold platform unit that is not protected by a guardrail system, crossbraces, vertical work surfaces or stirrups.

Scaffolding Terms (Continued)

Wood Plank Example
(Click to enlarge)

• Personal Fall Arrest System: An assembly of components and subsystems used to arrest a person in a fall from a working height.
• Plank: A wood board and fabricated component that serves as a platform unit.
• Plank (Metal): A metal platform united sized to support one or more workers or uniformly distributed loads. Metal planks would be similar dimensions as wood planks.
• Plank (Wood, Laminated): A platform unit of glue-laminated wood whose method of manufacture and assigned design values contemplate flat use in a scaffolding application.
• Plank (Wood, Sawn): A board of sawn lumber whose grading rules and assigned design values contemplate flat use in a scaffolding application.
• Platform: A general term for an elevated work surface composed of one or more platform units.
• Qualified Person: One who, by possession of a recognized degree, certificate, or professional standing, or who by extensive knowledge, training or experience has successfully demonstrated the ability to solve or resolve problems related to the subject matter, the work or the project.
• Rated Load: The manufacturer’s recommended maximum load.
• Runner: A horizontal scaffold member that forms a tie between posts and may also support a bearer.

Scaffolding Terms (Continued)

Safety Screen Example

• Safety Screen: A wire or plastic screening that protects the workers and passers-by below from dropped items.
• Scaffold: A temporary elevated or suspended work unit and its supporting structure used for supporting worker(s) or materials, or both.
• Sill: A footing (usually wood) which distributes the vertical loads to the ground or slab below.
• Tie: A device used between scaffold component and the building or structure to enhance lateral stability.
• Toeboard: A barrier secured along the sides and the ends of a platform unit to guard against the falling of material, tools and other loose objects.
• Toprail: The uppermost horizontal rail of a guardrail system.
• Working Load: Load imposed by persons, materials and equipment.

You can test your scaffolding vocabulary with an online crossword puzzle. It requires an Adobe Flash Player.

Who Uses Scaffolds

Workers on scaffolds can be divided into two groups, erectors/dismantlers and users:

Erectors/Dismantlers

Erectors and dismantlers are those workers whose are mainly responsible for assembling and disassembling scaffolding. This is done before other work can continue, and/or after work has been completed.

Training Requirements

OSHA requires employers to provide training by a competent person to each employee who is involved in erecting and/or disassembling a scaffold. A competent person must do adequate preplanning to make sure the scaffold is erected properly.

Preplanning includes:

• Determining the type of scaffold necessary for the job,
• Determining the maximum load of the scaffold,
• Assuring a good foundation, and
• Avoiding electrical hazards.

Users

Scaffold users are those whose work requires them, at least some of the time, to be supported by scaffolding. Employers are required to have a qualified person provide training to each employee who uses the scaffold.

Training Requirements

The training must teach employees to recognize the hazards associated with the type of scaffold being used. They must also understand the procedures to control or minimize those hazards. Here are a few of the hazards:

• Falls from elevation, due to lack of fall protection;
• Collapse of the scaffold, caused by instability or overloading;
• Being struck by falling tools, work materials, or debris; and
• Electrocution, principally due to proximity of the scaffold to overhead power lines.

Real-Life Scenario

In August, 1992, two workers were erecting an aluminum pump jack scaffold. As they were raising the second aluminum pole, the pole apparently contacted an overhead power line. The pole being raised was 29 feet 10 inches long and the line was 28 feet 10 inches high. The line was approximately 11 feet from the house. One employee died and the other suffered severe burns and was hospitalized. The surviving employee noted that he thought they had enough room to work around the power lines, which were not de-energized or shielded.

Final Words

That's a lot of information. It's now time for your first module quiz! Good luck!

Instructions

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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.

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