Scaffolding Hazards.
- General Safety.
- Statistics.
Poor scaffolds lead to accidents and injuries. 17% of fall
fatalities are from scaffolds.
Avoid the following
unsafe practices:
- Lean-to scaffolds
- Stacking materials too high
- Using poor quality lumber or plywood
- Types of Scaffolds.
- Tubular welded frame:
Most common, used by many trades.
- Tube and clamp / system scaffolds:
- Metal A-frame horse scaffolds:
Useful for both exteriors and interiors of buildings.
- Rolling scaffolds:
Provide easy access for many work activities.
- Design.
- Plumb
- Level
- Square
- Secure
Safety Tip: Never climb on an improperly built scaffold.
- Erection
Scaffolds must be
erected with:
- Fully planked platforms (no holes or gaps)
- Specially designed, scaffold-grade planks
- Base plates or sills under each leg
- Feet (minimum of 4” x 4”) or adjustable jacks
- Proper access, e.g., ladders
- Guardrails, midrails, and toe boards as needed.
- Competent Person.
Scaffolds must be erected, moved, and dismantled by a
trained crew under supervision of a designated:
Competent person: one who can identify existing and
predictable hazards in the surroundings or working conditions that are
unsanitary, hazardous, or dangerous to employees and who has authorization to
take prompt corrective measures to eliminate them.
- Qualified Person.
When supported metal scaffolds are built higher than 125’,
or the design is unusual, the design and erection must be approved by a
designated:
Qualified person: a person designated by the employer who,
by reason of training; experience; or instruction, has demonstrated the ability
to safely perform assigned duties and, when required, is properly licensed in
accordance with federal; state; or local laws and regulations.
- Hazards.
- OSHA Requirements.
Scaffold users must be properly trained in:
- Electrical exposures
- Fall protection
- Falling object protection
- Load capacities
- Electrical Hazards.
If power lines cannot
be deenergized (ideal), the worker and scaffold must be separated by at least:
- 3’ if lines are insulated and < 300 volts
- 10’ if lines are uninsulated or ≥ 300 volts
When distances cannot be maintained, isolating barriers or
mats must be installed.
- Fall Hazards.
Scaffold platforms > 10 feet require fall protection.
If guardrails cannot be used:
Fall arrest must be provided, including:
- Anchorages (able to support 5000 pounds)
- Full body harness and shock absorbing lanyards.
Make sure you know where to tie off and how. If you are unsure, check with your supervisor.
- Falling Object Hazards.
Tools and materials can easily fall from a scaffold to
injure someone below.
Toe boards are generally required.
- Over the front and rear face of the scaffold
- All levels over entries or access points
- Nominal dimension if materials piled > 4 inches
- Preparing for Scaffold Erection.
- Load Capacities and Frame Spacing.
- Light Trade: 10-foot frame space, 25 psf
- Medium Trade: 8-foot frame space, 50 psf
- Heavy Trade: 6-foot frame space, 75 psf
- Load Capacity.
- Frames
- If bearers are closer, planks can carry greater loads.
Load rating can be
determined by the spacing:
- Light trade: 10 feet apart
- Medium trade: 8 feet apart
- Heavy trade: 7 feet apart
- Load Rating
Calculate load capacity for a 5-foot-wide scaffold:
Light trade scaffold (10 feet between bearers):
5 feet x 10 feet = 50
square feet
Light duty rating =
25 pounds per square foot
25 psf X 50 sf = 1250
pounds
Heavy duty scaffold (7 feet between bearers):
5 feet x 7 feet = 35
square feet
Heavy duty rating = 75 pounds per square foot
75 psf X 35 sf = 2625
pounds
- Stability.
Scaffold legs carry loads:
- Of people, planking, frames, and equipment
- From platform heights to the ground
- Weighing between 2000 and 3000 pounds
Plates or sills must:
- Include no unstable materials
- Bear fully and evenly on the ground
- Follow manufacturer’s requirements.
- Access.
- Safe Access.
There are many ways to get on a scaffold, including:
- Ladders
- Attachable stairs
- Ramps from an upper level
- Climb from inside a structure
- Climbing.
Never climb frames unless they are designed for it.
- Sufficient space for your feet
- Wide enough to be climbed comfortably
- Evenly spaced
Never jump onto
scaffold platforms.
- Erection Standards.
- Erection Criteria.
At least 10” square base plates – 2” lumber or 1 ⅛” plywood.
4” square foot nailed to the base plate – On soil or
asphalt, use feet and pads or full sills between frames; on concrete, pads not
required.
Screw jack that slides into the scaffold frame leg – Not to
be extended more than ⅔ of full extension.
Tubular Welded Frame Scaffolds
Standard frames,
fixed width, and height
Equipment should all
be of the same: Manufacturer – Metal makeup.
Each frame has locking studs welded onto it that: – Accept cross braces for installation – Should function properly – Do not replace with wire.
Held together with cross braces.
Length of cross brace determines frame spacing – Maximum =
10 feet (light trade) – Minimum = 7 feet (heavy trade).
Cross braces must be: Undamaged, Secured properly on welded
studs of frames.
Connection Pins.
- Properly built scaffolds should:
- Carry loads directly to the ground.
- Distribute appropriately to the supporting soil.
- Remain fairly stable without special connections; However, in some conditions (e.g., wind, ladders on the outside frame), connection pins can secure and stabilize tubular welded frame scaffolds.
Guardrails / Toe boards.
Requirements:
- Minimum height (if made after 2000): 39 inches
- Maximum height (normally): 45 inches
- Midrails halfway between top rail and platform
- Toe boards (if necessary): At least 4” nominal, Protect the entire edge.
Securing to Structures.
Requirements for securing a scaffold include:
- When scaffold reaches 4 times its narrowest base dimension (e.g., 20 feet for a 5-foot-wide scaffold): secure and brace away from structure.
- Scaffolds less than 3 feet wide: secure every 30 feet horizontally and every 20 feet vertically
- Scaffolds wider than 3 feet: secure every 30 feet horizontally and every 26 feet vertically.
Other methods of security include:
Bolts and threaded connections and 9-gauge wire; However,
scaffold must be tied to and braced away from the structure to assure the
scaffold is stable for work.
- Planking.
- Fully Planked Platforms.
Fully planked means:
- Scaffold frame is covered from front to back
- No more than 1” spacing between planks
- No more than 10” space from backside of frame
- Must bear on supports at least 6”
- Cleat if planks move or cannot make minimum
- For continuous runs, planks must overlap 12”
- Wood Planks.
Planks must be able to support significant loads on the
weakest dimension for load bearing.
Scaffold grade with straight grain and no knots. Inspected
for quality before installation.
4:1 safety factor
means that the load rating for the plank is ¼ of the break strength of the
plank.
- Grading Scaffold Planks.
Identifying
scaffold-grade materials:
- Planks should be straight grained without knots.
- Southern Pine or Douglas Fir are common.
- Check for defects.
- Standard lumber should not be used.
- Other Types of Planks.
Some manufacturers have combined lightweight aluminum frames
with plywood platforms.
- Secured with hooks
- Fit specific types and lengths of scaffolds
Newer planks are made
of laminated veneer lumber:
- Much like manufactured “glu-lam” beams
- Stronger than naturally selected materials
- No lumber grading, but marked for compliance
- Removing Planks from Service.
Indications of
deteriorating quality include:
- Deep checking
- Full penetration cracks
- Significant warping
- Chemical damage
- Saw cuts
- Extreme deflection under load
- Supported Scaffolds.
- Spacing from Building or Wall.
For most trade work, a distance of 14” is allowed from the
front face of the scaffold frame to the face of the finished building (unless
guardrails on the interior face are provided).
Plastering operations allow a distance of 18”.
Work from outrigger bracket sections allows only 3”.
- Extensions.
When working on a scaffold, there are times when you cannot
reach some areas of work.
Do NOT use a ladder on top of a scaffold. As tempting as it might be!
- Inclement Weather.
Discontinue scaffold work:
- During stormy or high wind conditions
- If the scaffold is covered with ice or snow
- Rolling Scaffolds.
- Standards of Erection.
Rolling scaffolds can be made using tubular welded frames or
tube and coupler or system components; Or manufactured specifically as a
rolling scaffold.
The scaffold sits on
wheels.
- Must be plumb, level, and square
- Base-to-height ratio cannot exceed 4 times the narrowest dimension. Some states, e.g., CA, are more restrictive.
Rolling scaffolds must be built to prevent racking. Horizontal
diagonal braces between frames.
Like supported
scaffolds, rolling scaffolds require:
- Fully planked platforms
- Guardrails
- Midrails
- Toe boards
- Safe Use.
Safe use of rolling scaffolds requires:
- Level surfaces (within 3 degrees)
- Safe use of rolling scaffolds requires:
- Balanced loads
- No obstructions or holes
- No extensions (e.g., ladders, barrels, or boxes) . Never stand on scaffold rails.
- Wheels locked during work. No self-propelling or surfing
- Moving a Rolling Scaffold.
Self-propelling is not allowed; However, OK to be pushed
with specific controls:
- 2:1 base-to-height ratio
- Rider must hold on while moving
- Pusher pushes (not pulls) at a height of ~ 5 feet
- Floor within 3 degrees of level
- Floor must be free of holes, pits, and obstructions
- Access.
As with supported scaffolds, there are many ways to get onto
a rolling scaffold:
- External ladders
- Internal stairs
- Internal ladders
- Other stable options
- Inspection.
Rolling scaffolds must be inspected:
Daily before use. By a competent person.