Supported Scaffold Safety

An Overview of Scaffold Safety

May, 2011

Topics Covered

Scaffold hazards

Duties of a “competent person”

Basic scaffold requirements

Fall protection and guardrails

Employee training

Supported Scaffolds Examples

Supported scaffolds are scaffolds that are in contact with the ground rather than being suspended by cables.

Ladder jack scaffold

Mobile scaffoldFabricated frame scaffold

More Supported Scaffold Examples

Hazards of Scaffold Work

According to the scaffold industry association, the five most serious scaffold hazards are:

FallsUnsafe accessFalling objectsElectrocutionScaffold collapse

Falls, scaffold collapse and electrocution account for most scaffold related fatalities.

A combination of regular inspection and consistent training of workers can go a long way to reducing these risks.

Scaffold Collapse Can Happen

The safety of a scaffold is highly dependent upon being built right in the first place. When scaffolds fail, they fail in a catastrophic way and can cause many serious injuries or deaths depending on who is on or around it when it fails.

Damage Scaffold Parts

Damaged or weakened parts must immediately be:

• Repaired, replaced, braced to meet minimum strength

OR

• Removed from service until repaired.

Erecting, moving, altering or dismantling scaffolds

Must be supervised and directed by a competent person

Must be done by trained employees selected by a competent person

What is a “Competent Person”?

A competent person is able to:

• Identify existing and predictable hazards,

• Identify working conditions that are unsanitary, hazardous or dangerous and:

• Has authority to eliminate hazards.

Have knowledge of what the scaffolding standard requires for workplace safety training and experience in erecting and inspecting scaffolds,

know about the kinds of hazards that can exist around scaffolds,

be designated by management as the competent person,

have authority to take action to stop unsafe activities and eliminate hazards identified.

A competent person must:

Erecting and Dismantling Scaffolds

A “competent person” determines feasibility of fall protection, and

the employer must provide the maximum feasible fall protection.

Questions to ask are:•Is there a nearby structure from which a lifeline can be dropped that the worker can tie off to?•Can we install guardrails immediately after installing the fabricated frames and before moving to the next level?•Can we sequence disassembly to keep the worker protected for the maximum feasible time?Whatever is feasible to do must be done during the assembly/ disassembly stages.

While scaffolding is being erected or dismantled:

Fall Protection on Scaffold

• Employers must provide fall protection on a scaffold more than 10 feet above a lower level by one of these methods:

– Guardrails, which must be:

o Installed along open sides and ends and

o In place before employees use the scaffold

OR

– Personal fall arrest system

o In accordance with WAC 296-155 Part C-1 and WAC 296-874 -20052

o Must be attached to the structure or a lifeline and not the scaffold

Examples of Lack of Fall Protection

Requirements for Guardrails• Guardrails consist of toprail, midrail and falling

object protection, such as a toeboard

• The toprail must be between 38” – 45” high and withstand a 200 lb. force

• The midrail must be installed midway between the top edge and the platform surface and withstand a 150 lb. force

• A toeboard, when used, must be 3 ½ inches tall and able to withstand a 50 lb. force. Barricades at base of scaffold can be substituted for toeboard

GuardrailsCross bracing or “X” brace can substitute for top rail or mid rail but not both.

Cross bracing is acceptable in place of a midrail when the crossing point of two braces is between 20 inches and 30 inches above the work platform.

Cross bracing can be used as a top rail when the crossing point is between 38 inches and 48 inches above the work platform.

The end points at each upright must be no more than 48 inches apart.

Provide a Ladder, Ramp or Direct AccessFor platforms more than two above or below a point of access

In the picture on right, the worker is climbing the scaffold frame, which is in violation of the rule.

Power Line ClearanceInsulated power lines Uninsulated power lines

Less than 300 volts – 3 feet Less than 300 volts – 10 feet

- 300 volts – 50 kilovolts = 10 feet

- Over 50k Volts, add .4” per KV

Examples of scaffolds too close to power lines

You can get closer than these distances if you contact the power company and they deenergize the lines and visibly ground them or install protective shields.

Footings

Support the load without settling or displacement

Level

Sound

Rigid

A mud sill isn’t needed on a concrete surface or dry compacted soil. You always need the base plate.

Unstable Footing Examples

Cardboard, sticks, blocks, rocks or bricks aren’t a sound method of leveling

Platform Specifications

• Each working level fully planked; no more than 1” gaps

• Minimum platform and walkway width of 18”

• Overlap planks between scaffold sections by at least 12”

• Extend end over support 6” min. (Maximum end extension 12”)

• Don’t paint planks since they will hide defects

• Front edge within 14” of the work, or guard rails or fall protection must be used.

Scaffold platforms must be fully planked with no gaps greater than one inch.(and this employee needs fall protection)

Examples of Improper Scaffold Planking

Gaps too wide between planks

Planks can’t extend more than 18” beyond their support

If it’s not adequately secured, it can tip if you walk out past the support.If a plank extends too far past the support because it’s too long, you can barricade access to the hazardous area.

Plank Specifications

• Scaffold grade or equivalent

– 1,500 lb-f/in2 (stress grade) construction lumber

– Manufactured planks used according to manufacturer’s recommendations

Wood Plank Inspection

Damaged wood planks include:Rot - "squishy" feel, or powdery appearance from termite damage Cupping of 3/8" or more on a 10" wide or 1/2" or more on 12" wide plank.Crook of more than 5/16”, bow of more than 7/16” or twist of more than ¾” on a 10’ long 10” board.Wane of more than ¼ the width and ¼ the thickness for more than ¼ the length of the plank.A split that has a length of 1 ½ times the board width or more.Knots that are more than 1 ½” diameter if loose or 2” diameter if tight on a 10” plank.A notch cut into a plank more than 1/3 the plank width.Any saw kerf cut across the plank weakens the plank by the depth of the cut. The problem may not be noticed if the plank is later laid with the cut side down.

Plank Load Capacity

4 times the intended load + scaffold weight

Planks must not deflect more than 1/60 of span when loaded

Downward deflection must be no more than 1.8”

10’ total plank length 6” overlap

6” overlap

Examples of Overloaded Scaffolds

Overlaps

Angled plank is not on the bottom

Not fully planked at transition

No guardrail at transition

On a corner, planks that don’t come in at a right angle to the support must be on the bottom and then overlapped by the planks that are at a right angle.

Example of Unstable Support

Forklifts and front-end loaders are not designed by the manufacturer for such use.

Guying, Tying or Bracing

If the ratio of height to base is more than 4:1, then:

Install guys every 26’ above this tie point for scaffolds more than 3’ wide.Install these guys at each end of the scaffold and space additional middle guys no more than 30’ apart.

If you use a cantilevered work platform (outside the framework of the scaffold), then you must use some type of bracing such as tying or outriggers to prevent the scaffold from tipping.

Other Scaffold Use Rules

Don’t • Move a scaffold when someone

is on it.

• Work on a scaffold covered with snow or ice.

• Work on a scaffold during a storm or high winds.

• Use boxes, barrels or a ladder on top of a scaffold to increase its height.

Do clean up debris on platforms before it accumulates.

Unacceptable Scaffold Example• Shore or “lean to”

• Also, a competent person must approve the use of dissimilar metals

• Intermixed scaffold components must fit together without force and not effect the structural integrity of the scaffold.

This is an example of a lean-to scaffold. In this picture, the workers have a shore scaffold on top of another shore scaffold. Access is unsafe both from above and below. The only thing holding this scaffold up is the DUMPSTER!

Worker Must Be Trained On:• Recognizing hazards of the type of scaffold they’ll be using

• Understanding the procedures to control or minimize hazards

• How to erect, maintain and disassemble the fall protection and falling object protection systems

• Using the scaffold and handling materials on the scaffold

• Maximum intended load and capacity

• Other information as needed

Employees need training so they don’t misuse the scaffold or do things that will cause it to lose its integrity, such as removing cross bracing so they can do their work. Training needs to be specific to the scaffold the workers will be using. Job-specific issues would include power line clearances, surface conditions.

Worker Must Be Retrained When:• You believe an employee lacks the skill or understanding

to safely erect, use or dismantle a scaffold

• If an employee's work is inadequate

• If there is a change in any of the following that presents new hazards:

– Worksite

– Type of scaffold

– Fall protection

– Falling object protection

– Other equipment

Additional InformationDOSH Scaffolds Rules: WAC 296-874, Scaffolds

Scaffold Accident Video – A Life-Changing Moment

OSHA – Scaffolding eTool

YouTube – Scaffold Safety

CPWR – Scaffold Safety Hazard Alert

Oregon OSHA – Supported Scaffolds in Construction

Oregon OSHA – Scaffold Safety (Spanish)