Scaffolding Safety
The year 2023 began with a scaffolding collapse in Charlotte, killing 3 and injuring 2 workers. A month later, another scaffold collapsed in Chicago and injured 2 workers. Last month, a scaffolding collapse injured 2 pedestrians and damaged a street light in Toronto.
Scaffolds surround the skyscrapers of many cities, making them a popular choice for construction and maintenance work. A scaffold is an elevated temporary platform that allows employees to perform various tasks at higher heights or hard to reach places.
Working at heights always poses a falling hazard, be it falling objects, falling workers, or both. Some workers have even fallen from a height of 200 feet. In 2020, the U.S. Bureau of Labor Statistics reported a total of 3,250 scaffolding-related injuries and 52 fatalities.
Scaffolds fall into two main categories: Suspended scaffolds and supported scaffolds. Suspended scaffolds hang off a structure with ropes or cables. Supported scaffolds sit on top of a strong support structure made of poles, frames, and load-bearing members.
This post will focus on supported scaffolds.
Scaffolds endanger both public and occupational safety. Supported scaffolds require a firm foundation along with plumb (perfectly vertical) and braced support structures.
Both forms of scaffolding need sturdy guardrails and safe access points. The dangers of scaffolding also demand daily inspections, training, and personal protective equipment (PPE), such as an effective fall arrest system.
A SOUND STRUCTURE
A scaffolding collapse must always prompt an inspector or manager to question the integrity of the structure. A strong structure, for the most part, should not sway in the wind or break under its own weight.
The Base
A solid base initiates stability for all supported scaffolds. A tall structure can never stay put on uneven or slanting ground. All supported scaffolds must be set on base plates and mudsills.
Base plates: A base plate is a thin, flat slab of steel that attaches to the bottom of a column. The plate allows for the weight of the column to be distributed across a wider surface area, hence improving stability. The plate comes with holes to insert bolts and an extension to connect a column.
Mudsills: The bolts fasten the base plate to the mudsill, a larger layer of flat wood that allows for a greater distribution of weight.
Support Structures
Supported scaffolds, as the name suggests, require support structures to prop up the platform in place. Support structures normally include standards, ledgers, and braces. All these members must be secured using joints, hooks, or pins.
Standards: Standards include all the vertical members such as upright columns, poles or tubes. These members add height to the scaffold and must be completely plumb or perfectly vertical.
Plumbness ensures stability and transfers the weight of the scaffold straight down to the base plate and mudsill. Plumb structures maximize the load-bearing capacity as opposed to slanting members that suffer extra stress when exposed to weight. Levels or plumb bobs can help determine plumbness.
Ledgers: The horizontal beams, known as ledgers, link the standards together. Ledgers enhance stability and prevent the structure from falling over. These horizontal members also support platforms, providing a rigid work surface.
Braces: To establish full stability for the scaffolding structure, braces run diagonally through the standards and tie the whole structure together.
Remaining Upright
Despite installing plumb standards with ledgers and braces, a scaffolding system may still lose its balance as it increases in height. The general rule of thumb suggests that a scaffold becomes unstable if its height exceeds four times its base dimensions. Extreme weather conditions may also cause a scaffold to topple.
Ties act as an anchorage system that fastens the scaffold to the building or another rigid body. An example of a tie system includes guy wires. Guy wires are tension cables that extend from the scaffold to the ground in a diagonal manner to prevent it from tipping over.
The Platform
The platform may be frequented by workers in construction, maintenance, project management, sales, or health and safety. The platform rests on top of several ledgers and contains planks or decking to provide safe flooring for workers. Planks or decking can be made out of wood or metal.
Some planks may have small gaps between them, depending on the job at hand. Plank gaps cannot exceed 1 inch. Platforms must also be at least 18 inches wide to accommodate proper movement.
Guardrails
Guardrails must contour all open sides and ends of a scaffolding platform. Guardrails protect workers from suffering fatal falls and normally stretch between 39 and 48 inches in height. Guardrails, being an engineering control, provide one of the best forms of defense against falling hazards.
A guardrail system includes top rails, mid rails, mesh, and balusters (vertical posts) to prevent workers from sliding out from underneath the railing. Top rails should be able to withstand at least 200 pounds of force to provide a safe barrier between the worker and the drop. The midrail should withstand 150 pounds.
Toe Boards and Mesh
When working on scaffolds, workers may take their tools and other materials and place it on the platform for easy reach. These objects can accidentally get kicked off the surface and end up falling on other workers below. Toe boards act as a barricade and line the edge of a platform to prevent items from falling over. These boards must be 3.5 inches in height and be able to withstand a force of 50 pounds.
Covering scaffolds with mesh also prevents construction debris from escaping the platform and affecting other persons or the environment.
Load Capacity
Scaffolds must be able to support their own weight plus at least 4 times their maximum intended load. In mathematical terms, the scaffolding load capacity (SWL) is equal to the dead load (DL) capacity + 4 times the live load (LL) capacity or SWL = DL + 4 (LL).
The dead load refers to the weight of a completed structure before any form of operation. The live load includes the moving or movable loads that may be added to the structure during operation.
Companies must refrain from overloading a scaffold beyond its capacity. Live loads can include extra people or extra materials on the platform. Concentrating loads on one part of the platform can also overload the scaffold.
Access Points
Workers can easily lose their balance when climbing on or off a scaffold. Scaffold braces and ledgers are not meant for climbing and can detach and collapse under misuse. OSHA specifically forbids climbing scaffold members.
Scaffold erectors must ensure safe means of access and egress such as ladders, ramps, stairwells, walkways, or elevators. Ladders, if built into the scaffolding structure, should remain vertical and include resting platforms every 25 feet along with anti-slip treads. Ramps, stairwells, and walkways should have proper guardrails. Stairwells must be built at a 60 degree angle or less, while ramps should not exceed a 20 degree angle. Elevators can save time, reduce fatigue, and allow workers to carry many materials and equipment at the same time.
ELECTRICAL HAZARDS
Many scaffolds, often made of metal, pose a serious electrical hazard when they tower near power lines. Metal, being a strong conductor of electricity, can put workers at risk of electrocution.
Erect scaffolds at least 10 feet away from uninsulated power lines that exceed 300 volts. Keep in mind that some metal tools like long paint rollers can still make contact with a power line despite the distance. Companies should substitute these metal tools with non-conductive tools to alleviate this risk.
Conductive materials can also line conduits and pipes. All conduits and pipes must be secured away from any electrical source. When using electrical power tools, ensure the grounding prong on the plug and a ground-fault circuit interrupter (GFCI) receptacle.
If workers must go closer than 10 feet, OSHA mandates that companies call the local utility provider to de-energize the power lines or provide proper insulation.
WEATHER ELEMENTS
Thunderstorms, snow, and ice can result in slippery conditions on platforms and accessways, possibly leading to falls. Lightning can also strike a taller scaffold and endanger workers on top, not to mention the entire scaffolding structure. Extreme wind can also cause scaffolds to collapse, especially if they haven’t been erected, tied, or maintained properly.
To ensure safety for workers, companies must prohibit work during extreme weather conditions. Extreme temperatures can also affect people working at heights, leading to heat stress or cold stress.
After being hit with stormy or snowy weather, companies must address all slippery surfaces and remove remnants of ice, large puddles, and debris.
THE FALL ARREST SYSTEM AND PPE
In addition to guardrails, all workers must don a full-body harness with a lanyard that can attach to an anchor point. OSHA mandates the use of a harness when working at a height of 10 feet or over.
The full-body harness consists of adjustable straps that fit around the worker’s chest, thighs, shoulders, hips, and back. During a fall, the full-body harness distributes the force of the fall across the entire body. The lanyard clips the harness to the anchor point in order to “arrest” a fall and prevent the person from hitting the ground. The lanyard also helps restrict movement on the platform itself. Together, the anchor point, lanyard, and harness make up the fall arrest system, with the harness constituting as PPE.
When a worker falls off a platform, the fall-arrest system has them vertically hanging in the air, which can pose its own dangers. Dangling in the air can cause blood to pool at the feet, causing suspension trauma, unconsciousness or even death. Workers who fall must be rescued within 5–10 minutes to avoid fatal consequences.
To save a worker on time, companies must build a Fall Rescue Plan prior to starting any work on scaffolds. The plan indicates steps, reporting paths, contact information, resources, tools, and equipment for effective emergency rescues.
An ill-fitting harness can also induce additional harm during a fall. For example, a harness fitting on the wrong side of the chest or shoulders can cause additional injury, reduce the protection factor, or cut off circulation. Women especially need to take extra precautions when choosing a harness.
The best way to protect workers is to prevent falls all together. Keep away from power lines (electrocution can also push a person off a platform), remove slip and trip hazards, and maintain sturdy guardrails and toe boards.
INSPECTIONS
Scaffolds require pre-use inspections to detect abnormalities before each work shift. Inspections may look for structural integrity, ladder defects, slippery conditions, tripping hazards, plank damages, anchorage issues, or weakening tie or guy wire systems. Companies should assign a “competent person” to conduct inspections, meaning that this person should have the ability to identify hazards and have the authority to control them.
Full-body harnesses, lanyards and hooks must also be inspected properly by the wearer. Any damages or rips can affect the protection factor of a harness or lanyard.
TRAINING
Scaffolding safety cannot move forward without knowledgeable workers. All workers must complete a certified training on fall protection and working at heights. Some jurisdictions require re-certification every 3 or 4 years as well. The certified training gives a broad overview of how to work at heights, identify hazards, and use a fall-arrest system.
However, simply sending workers to an external training program does not fully prepare them for the dangers on the specific job-site. The company must also provide additional training to promote awareness of site-specific hazards and controls. This training may cover different company policies, PPE requirements, hazardous materials at the site, housekeeping methods, thermal stress, incident reporting, and fall rescue planning.
These topics can be covered during an orientation, daily safety huddles, or toolbox talks. Communicating with workers brings the team together to work towards the same goal, the goal of safety.
REFERENCES
ETool : Scaffolding — supported scaffolds — frame or fabricated. (n.d.). Osha.gov. Retrieved May 1, 2023, from https://www.osha.gov/etools/scaffolding/supported/frame
Guidelines for Guying and Tying off Scaffolds. (2010, July). Saiaonline.org. https://www.saiaonline.org/files/SSFI%20Tech%20Bulletin_Guidelines%20for%20Guying%20and%20Tying%20of%20Scaffolds.pdf
Scaffolds — access and egress. (n.d.). Ihsa.Ca. Retrieved May 2, 2023, from https://ohsguide.ihsa.ca/en/topic/scaffolds_access.html
Supported Scaffold Inspections. (n.d.). Oshatrain.org. Retrieved May 2, 2023, from https://www.oshatrain.org/courses/pdf/QCsupported_scaffold_tips2.pdf
